# Morbidity and Mortality Weekly Report
www.cdc.gov/mmwr



## Surveillance Summaries September 12, 2008 / Vol. 57 / No. SS-9



# Surveillance for Waterborne Disease and Outbreaks Associated with Recreational Water Use and Other Aquatic Facility-Associated Health Events — United States, 2005–2006 and Surveillance for Waterborne Disease and Outbreaks Associated with Drinking Water and Water not Intended for Drinking — United States, 2005–2006

depar tment of health and human ser vices Centers for Disease Control and Prevention Centers for Disease Control and Prevention

### MMWR

The MMWR series of publications is published by the Coordinating Center for Health Information and Service, Centers for Disease Control and Prevention (CDC), U.S. Department of Health and Human Services, Atlanta, GA 30333.
Suggested Citation: Centers for Disease Control and Prevention. [Title]. Surveillance Summaries, [Date]. MMWR 2008;57(No. SS-#).
Centers for Disease Control and Prevention Julie L. Gerberding, MD, MPH Director Tanja Popovic, MD, PhD Chief Science Officer James W. Stephens, PhD Associate Director for Science

Steven L. Solomon, MD Director, Coordinating Center for Health Information and Service Jay M. Bernhardt, PhD, MPH Director, National Center for Health Marketing Katherine L. Daniel, PhD Deputy Director, National Center for Health Marketing

Editorial and Production Staff Frederic E. Shaw, MD, JD

Editor, MMWR Series Susan F. Davis, MD ( Acting ) Assistant Editor, MMWR Series Teresa F. Rutledge Managing Editor, MMWR Series David C. Johnson ( Acting ) Lead Technical Writer-Editor

Patricia A. McGee

Project Editor Peter M. Jenkins ( Acting ) Lead Visual Information Specialist Malbea A. LaPete Stephen R. Spriggs Visual Information Specialists Kim L. Bright, MBA Quang M. Doan, MBA Erica R. Shaver Information Technology Specialists

Editorial Board William L. Roper, MD, MPH, Chapel Hill, NC, Chairman Virginia A. Caine, MD, Indianapolis, IN

David W. Fleming, MD, Seattle, WA William E. Halperin, MD, DrPH, MPH, Newark, NJ Margaret A. Hamburg, MD, Washington, DC

King K. Holmes, MD, PhD, Seattle, WA Deborah Holtzman, PhD, Atlanta, GA John K. Iglehart, Bethesda, MD Dennis G. Maki, MD, Madison, WI Sue Mallonee, MPH, Oklahoma City, OK Patricia Quinlisk, MD, MPH, Des Moines, IA Patrick L. Remington, MD, MPH, Madison, WI

Barbara K. Rimer, DrPH, Chapel Hill, NC John V. Rullan, MD, MPH, San Juan, PR

William Schaffner, MD, Nashville, TN

Anne Schuchat, MD, Atlanta, GA Dixie E. Snider, MD, MPH, Atlanta, GA John W. Ward, MD, Atlanta, GA 

### CONTENTS

Surveillance for Waterborne Disease and Outbreaks Associated with Recreational Water Use and Other Aquatic Facility-Associated Health Events — United States, 2005–2006 **Introductio n .........................................................................**  **2 Background** 

**......................................................................... 3** 
**Methods**

**.............................................................................. 4** 
**Results**

**................................................................................. 6** 
**Discussion**

**......................................................................... 14** 
**Conclusion**

**........................................................................ 25** 
**References**

**......................................................................... 26**  **Appendices**

**....................................................................... 30** 

Surveillance for Waterborne Disease and Outbreaks Associated with Drinking Water and Water not Intended for Drinking — United States, 2005–2006 **Introductio n .......................................................................**  **39 Background** 

**....................................................................... 40** 
**Methods**

**............................................................................ 41** 
**Results**

**............................................................................... 44** 
**Discussion**

**......................................................................... 52** 
**Conclusion**

**........................................................................ 59** 
**References**

**......................................................................... 61**  **Appendices**

**....................................................................... 63** 



### On the Cover ( left to right ) : A child filling a cup with tap water. A man standing in a natural body of water. Young children playing in a swimming pool.

### 1 **Vol. 57 / SS-9 Surveillance Summaries** 


# Surveillance for Waterborne Disease and Outbreaks Associated with Recreational Water Use and Other Aquatic Facility-Associated Health Events — United States, 2005–2006

Jonathan S. Yoder, MSW, MPH 1 Michele C. Hlavsa, MPH 1 Gunther F. Craun, MPH 2 Vincent Hill, PhD 1 Virginia Roberts, MSPH 1,3 Patricia A. Yu, MPH 4 Lauri A. Hicks, DO 5 Nicole T. Alexander, MPH 5 Rebecca L. Calderon, PhD 6 Sharon L. Roy, MD 1 Michael J. Beach, PhD 1
1 Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases, CDC 2 Gunther F. Craun and Associates, Staunton, Virginia 3 Atlanta Research and Education Foundation 4 Division of Foodborne, Bacterial, and Mycotic Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases, CDC 5 Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases 6

U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 

## Abstract

Problem/Condition: Since 1971, CDC, the U.S. Environmental Protection Agency, and the Council of State and Territorial Epidemiologists have collaboratively maintained the Waterborne Disease and Outbreak Surveillance System for collecting and reporting data related to waterborne-disease outbreaks (WBDOs) associated with drinking water. In 1978, WBDOs associated with recreational water (natural and treated water) were added. This system is the primary source of data regarding the scope and effects of disease associated with recreational water in the United States. In addition, data are collected on individual cases of recreational water-associated illnesses and infections and health events occurring at aquatic facilities but not directly related to water exposure. Reporting Period: Data presented summarize WBDOs and case reports associated with recreational water use that occurred during January 2005–December 2006 and previously unreported disease reports and outbreaks during 1978–2004. Description of the System: Public health departments in the states, territories, localities, and the Freely Associated States (i.e., the Republic of the Marshall Islands, the Federated States of Micronesia, and the Republic of Palau, formerly parts of the U.S.-administered Trust Territory of the Pacific Islands) have primary responsibility for detecting, investigating, and voluntarily reporting WBDOs to CDC. Although the surveillance system includes data for WBDOs and cases associated with drinking water, recreational water, and water not intended for drinking, only cases and outbreaks associated with recreational water and health events at aquatic facilities are summarized in this report. Results: During 2005–2006, a total of 78 WBDOs associated with recreational water were reported by 31 states. Illness occurred in 4,412 persons, resulting in 116 hospitalizations and five deaths. The median outbreak size was 13 persons (range: 2–2,307 persons). Of the 78 WBDOs, 48 (61.5%) were outbreaks of gastroenteritis that resulted from infectious agents or chemicals; 11 (14.1%) were outbreaks of acute respiratory illness; and 11 (14.1%) were outbreaks of dermatitis or other skin conditions. The remaining eight were outbreaks of leptospirosis (n = two), primary amebic meningoencephalitis (n = one), and mixed or other illnesses (n = five). WBDOs associated with gastroenteritis resulted in 4,015 (91.0%) of 4,412 illnesses. Fifty-eight (74.4%) WBDOs occurred at treated water venues, resulting in 4,167 (94.4%) cases of illness. The etiologic agent was confirmed in 62 (79.5%) of the 78 WBDOs, suspected in 12 (15.4%), and unidentified in four (5.1%). Thirty-four (43.6%) WBDOs had a parasitic etiology; 22 (28.2%), bacterial; four (5.1%), viral; and two (2.6%), chemical or toxin. Among the 48 gastroenteritis outbreaks, Cryptosporidiumwas Corresponding author: Jonathan S. Yoder, MSW, MPH, Division of Parasitic 

### confirmed as the causal agent in 31 (64.6%), and all Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases, 4770 

### except two of these outbreaks occurred in treated water Buford Hwy., NE, MS F-22, Atlanta, GA 30341. Telephone: 770-488-3602; Fax: 770-488-7761. E-mail: jey9@cdc.gov. 

### venues where Cryptosporidium caused 82.9% (29/35) of the gastroenteritis outbreaks.

### 2 **MMWR September 12, 2008** 



### Case reports associated with recreational water exposure that were discussed and analyzed separately from outbreaks include three fatal Naegleria cases and 189 Vibrio illnesses reported to the Cholera and Other Vibrio Illness Surveillance System. For Vibrio reporting, the most commonly reported species were Vibrio vulnificus

, V. alginolyticus , and V. parahaemolyticus

. V. vulnificus illnesses associated with recreational water exposure had the highest Vibrioillness hospitalization (77.6%) and mortality (22.4%) rates. In addition, 32 aquatic facility-related health events not associated with recreational water use (e.g., pool chemical mixing accidents) that occurred during 1983–2006 were received from New York. These events, which caused illness in 364 persons, are included in this report but analyzed separately. Interpretations: The number of WBDOs summarized in this report and the trends in recreational water-associateddisease and outbreaks demonstrate a substantial increase in number of reports from previous years. Outbreaks, especially the largest ones, occurred more frequently in the summer at treated water venues and caused gastrointestinal illness. Deficiencies leading to WBDOs included problems with water-quality, venue design, usage, and maintenance. Case reports of illness associated with recreational water use expand our understanding of the scope of waterborne illness by further underscoring the contribution of less well-recognized swimming venues (e.g., oceans) and illness (e.g., nongastrointestinal illness). Aquatic facilities are also a focus for injuries involving chemicals or equipment used routinely in the operation of swimming venues, thus illustrating the lack of training of some aquatics staff.
Public Health Actions: CDC uses WBDO surveillance data to 1) identify the etiologic agents, types of aquatic venues, water-treatment systems, and deficiencies associated with outbreaks and case reports; 2) evaluate the adequacy of efforts (i.e., regulations and public awareness activities) to provide safe recreational water; 3) expand the scope of understanding about waterborne disease and health events associated with swimming and aquatics facilities; and 4) establish public health prevention priorities, data, and messaging that might lead to improved regulations, guidelines, and prevention measures at the local, state, and federal levels.



# IntroductionDuring 1920–1970, statistical data regarding waterbornedisease outbreaks (WBDOs) in the United States were collected by different researchers and federal agencies ( 1 ). Since 1971, CDC, the U.S. Environmental Protection Agency(EPA), and the Council of State and Territorial Epidemiologists (CSTE) have collaboratively maintained the Waterborne Disease and Outbreak Surveillance System (WBDOSS), a surveillance system that tracks the occurrences and causes of WBDOs and cases of disease associated with drinking water (2–11 ). In 1978, WBDOs associated with recreational water were added to the surveillance system. The types of outbreaks and disease case reports included in the Surveillance Summaries have expanded multiple times to more accurately reflectthe scope of waterborne disease in the United States. Outbreaks of Pontiac fever (PF) were added in 1989 (9), outbreaks of Legionnaires’ disease (LD)were added in 2001 (3,12 ), and single cases of Vibrioillness reported to the Cholera and Other VibrioIllness Surveillance System that were associated with recreational water use were added in 2003. WBDOs associated with drinking water and water not intended for drinking are presented in a separate report ( 13 ). WBDO surveillance activities are intended to 1) characterize the epidemiology of waterborne disease; 2) identify trends in the etiologic agents and other factors associated with WBDOs; 3) identify major deficiencies in pr oviding safe recreational water; 4) encourage public health personnel to detect and investigate WBDOs; 5) foster collaboration among local, state, federal, and international agencies on initiatives to prevent waterborne disease; and 6) collect data needed to support future prevention efforts. Additional data on cases of waterborne disease related to recreational water are gatheredfrom separate disease surveillance systems and through supplementary surveillance activities (Figure 1). Some of these dataare collected and analyzed in WBDOSS, and some are discussed in this report. These data are useful for expanding our understanding of the scope of waterborne disease, identifyingimportant factors associated with unsafe or unhealthy recreational water, influencing research priorities, supporting public health recommendations, and encouraging improved water-quality policies and regulations. However, WBDOs andcase reports summarized in this report are thought to represent only a portion of the illness associated with recreationalwater exposure. Reliable estimates of the number of unrecognized WBDOs are not available. In addition, the surveillanceinformation described in this report does not include estimates of the number of recreational water illnesses (RWIs).

### 3 **Vol. 57 / SS-9 Surveillance Summaries** 

**FIGURE 1. D**  **ata sources and outputs of the Waterborne Disease and Outbreak Surveillance System**

Waterborne disease outbreaks (WBDOs) reported routinely to CDC by jurisdictional health authorities (e.g., states and territories) Single water-associated cases of • Primary Amebic Meningoencephalitis

(e.g., ) • Chemical/toxin poisoning • Wound infections (reported sporadically

by some jurisdictional health authorities) Naegleria fowleri

Aquatic facility-related health events not associated with recreational water (reported sporadically by jurisdictional health authorities) Recreational water-associated Vibrio cases (reported separately to the Cholera and Other Surveillance System) Vibrio

Periodic reports of waterbornedisease outbreaks Waterborne Disease and Outbreak

(recreational, drinking, and other uses) published biennially in Surveillance Summaries

MMWR Analysis of waterborne disease and outbreaks and dissemination of waterborne-disease prevention messages Waterborne Disease and Outbreak Surveillance System (WBDOSS)

Use of surveillance data by public health researchers and policy makers to understand and reduce waterborne disease and outbreaks



# Background EPA sets guidelines for recreational use of natural waters(e.g., lakes, rivers, and oceans). In 1986, EPA developed rec

## Regulation of Recreational Water ommended bacterial water-quality criteria for coastal recre

## Quality ation waters ( 16 ) and recently established federal standards for those states and territories that have not yet adopted In the United States, state and local governments establish water-quality criteria that meet or exceed the 1986 criteria and enforce regulations for protecting recreational water from ( 17 ). For freshwater, full-body contact beaches (e.g., lakes and naturally occurring or human-made contaminants. For treated rivers), EPA has recommended that the monthly geometric water venues (e.g., swimming pools and water parks), no fed­ mean water-quality indicator concentration be <33 CFU/100 eral regulatory agency has authority, and no national guide­ mL for enterococci or <126 CFU/100 mL for Escherichia coli

. lines for standards of design, construction, operation, For marine-water, full-body contact beaches, EPA has recom­ disinfection, or filtration exist, except recent regulation to pre­ mended that the monthly geometric mean water-quality vent entrapment injuries ( 14 ). Swimming pool codes are indicator concentration be < 35 CFU/100 mL for enterococci. developed and enforced by state and local health departments; However, state and local authorities have discretionary therefore, substantial variation is observed across the country authority to determine which interventions should be used in terms of policy, compliance, and enforcement ( 15 ). Efforts (e.g., posting signs to alert visitors of water contamination or are underway to develop a Model Aquatic Health Code (avail­ closing the beach for swimming) when these limits have been able at http://www.cdc.gov/healthyswimming/model_code.htm) exceeded. Beach Watch, EPA’s Action Plan for Beaches and to be used as a national voluntary guideline. These data-driven Recreational Waters (report available at http://www.epa.gov/ and knowledge-based guidelines will be focused on promot­ waterscience/beaches/technical.html), was published in 1999 ing healthy recreational water experiences by preventing dis­ as part of the Clean Water Action Plan (available at http:// ease and injuries. The model code will be available to state www.epa.gov/beaches). The intent of Beach Watch is to assist and local health agencies needing guidance in writing, updat­ state, tribal, and local authorities in strengthening and extend­ ing, and implementing state or local pool codes and might ing existing programs to protect users of fresh and marine rec­ help standardize pool codes across the United States. reational waters; as part of the BEACH Act of 2000, the U.S. Congress directed EPA to update its guidelines for recreational

### 4 **MMWR September 12, 2008** 



### water use on the basis of improved water-quality indicators and testing. As a result, EPA has been collaborating with CDC since 2002 on the National Epidemiologic and Environmental Assessment of Recreational (NEEAR) Water Study at fresh andmarine water recreational beaches in the United States. Information on the NEEAR is available at http://www.epa.gov/ nheerl/neear. This study is being conducted to evaluate rapid new water-quality methods that are able to produce results in <2 hours and to correlate these indicators with health effects among beachgoers. Results from freshwater Great Lakes beaches have demonstrated an association between an increasing signal detected by a quantitative polymerase chain reaction-based test method for enterococci and human health effects ( 18, 19 ). Children aged <10 years were at greater risk for gastrointestinal illness following exposure ( 19 ) to water with elevated levels of enterococci.



# Methods

Data Sources

Public health departments in individual states, territories, localities, and the Freely Associated States (FAS)* have the primary responsibility for detection and investigation of WBDOs. The outbreaks are voluntarily reported to CDC through a standard form (i.e., CDC form 52.12; available at http://www.cdc.gov/healthyswimming/downloads/cdc_5212_waterborne.pdf). The form solicits data on WBDO, including characteristics of person, place, and time and results of epidemiologic studies, disease symptoms, diagnostic testing,and water sampling. Information gathered regarding the setting of the outbreak includes the type of aquatic facility, watersource and treatment, sanitary measures in place, and possible factors contributing to the contamination of the water.Public health professionals in each state or locality are designated as WBDO surveillance coordinators, and CDC annually requests reports from coordinators in all states and localities and conducts as much follow-up correspondence as neededto resolve unaddressed questions. Although national reporting only includes WBDOs, single cases of certain waterborne diseases (e.g., primary amebic meningoencephalitis (PAM) andchemical toxin poisoning) are also solicited from coordinators. Outbreaks, cases, or other health events, where applicable, are assigned to a state on the basis of the location of the exposure rather than state of residence of ill persons. Numeric and text data from the CDC waterborne disease outbreak form and any supporting documentation are entered into a data­

* Composed of the Republic of the Marshall Islands, the Federated States of

Micronesia, and the Republic of Palau; formerly parts of the U.S.-administered Trust Territory of the Pacific Islands. 

### base for analysis. Although all WBDOs are collected throughthe same CDC reporting system, the recreational waterassociated outbreaks are analyzed and published separately from drinking water-associated outbreaks and other WBDOs ( 13 ). Information on WBDOs and cases is sometimes solicited from other CDC surveillance systems and confirmed with the state or locality for inclusion in WBDOSS or Surveillance Summary (Figure 1). Vibrio illnesses associated with recreational water exposure were received from the Cholera and Other VibrioIllness Surveillance System.



## Definitions †



### Waterborne Disease Outbreaks

The unit of analysis for the summary is an outbreak, not an individual case of a waterborne disease. To be defined as a WBDO associated with recreational water, an event must meettwo criteria. First, two or more persons must be epidemiologically linked by the location of the exposure to recreational water, time, and illness. Recreational water settings include swimming pools, wading pools, spas, waterslides, interactive fountains, wet decks, and fresh and marine bodies of water. Second, the epidemiologic evidence must implicate water orvolatilization of water-associated compounds into the air surrounding an aquatic facility as the probable source of the illness. For this report, WBDOs are separated by venue as untreated (i.e., fresh and marine surface water) or treated (i.e., filtered or disinfected [e.g., chlorinated]) water. WBDOs associated with ships are not included in this report.


## Case Reports of Waterborne Illness or Reports of Aquatic Facility-Associated Health Events

This report also includes 1) individual cases of laboratoryconfirmed PAM associated with recreational water use, 2) single cases of wound infections or other Vibrioinfections associated with recreational water use, 3) single cases of chemical and toxin poisoning if water or air-quality data indicate contamination by the chemical or toxin, and 4) outbreaks or case reports of health events associated with aquatic facilitiesbut not associated with the recreational water but rather contaminated aquatic facility air (e.g., mixing of chemicals in thepump room might release toxic gas that injures staff or facility users) (Figure 1). Because these four event categories do not meet WBDO definition, they are analyzed separately from WBDOs.

† Additional terms have been defined (Appendix A, Glossary of Definitions).

### 5 **Vol. 57 / SS-9 Surveillance Summaries** 


## Strength of Evidence Classification for Waterborne-Disease Outbreaks

WBDOs reported to WBDOSS are classified according to the strength of evidence that implicates water as the vehicle of transmission (Table 1). The classification scheme (i.e., Classes I–IV) is based on the epidemiologic and water-quality data provided on WBDO report form. Although in certain instances WBDOs without water-quality data were included in this report, outbreaks that lacked any epidemiologic data linking the outbreak to water were excluded.

Class I indicates that adequate epidemiologic and waterquality data were reported (Table 1). However, the classification does not necessarily imply that an investigation was conducted optimally. Likewise, a classification of II, III, or IV does not imply that an investigation was inadequate orincomplete. Outbreaks and investigations occur under varying circumstances, and not all outbreaks can or should be rigorously investigated. In addition, outbreaks that affect fewer persons are more likely to receive classifications of III or IV because of the limited sample size available for data analysis.


## Changes in the 2005–2006 Surveillance Summary

The definition of a waterborne outbreak has been modified for this report to be consistent with generally accepted public health practice (i.e., two or more epidemiologically linked cases associated with use of recreational water). Health events ataquatic facilities not associated with direct exposures to recreational water are, for the first time, presented and discussed but not analyzed as waterborne outbreaks. DefinitionPreviously, the definition of a recreational waterborne disease outbreak included certain single cases of waterborne disease. The definition of a recreational waterborne-disease outbreak has been clarified to include two or more persons who have been epidemiologically linked to recreational water by location of exposure, time, and illness. Exposures include contact with or accidental ingestion of water and certaininhalation exposures (e.g., exposure to water-associated compounds [e.g., chloramines] volatilizing into the air of theaquatic facility). Single cases of PAM, recreational waterassociated Vibrioillness, and illness related to chemical exposure caused by water are included in WBDOSS but are not classified or analyzed as outbreaks. These single cases are analyzed separately. Aquatic Facility-Related Health Events not Associated with Recreational Water

Previous Surveillance Summaries only included outbreaks inwhich the vehicle of transmission was water or airborne chemical products originating from water (e.g., chloramines). Nonwater-related illnesses resulting from chemical inhalation or exposure at aquatic facilities have not been discussed in previous Surveillance Summaries. This report includes, as aseparate analysis, chemical injury (e.g., mixing of pool chemicals that release toxic gas) cases and outbreaks at aquatic facilities in which direct exposure to water was not the cause of illness. Whereas these events are not classified or analyzed as waterborne outbreaks, they highlight important public health and safety concerns related to the design, operation, and maintenance of recreational water venues and are targeted to the same audiences who are the focus of the waterborne disease and outbreaks already included in this report.

**TABLE 1. Classification of investigations of waterborne-disease outbreaks based on strength of evidence inplicating water as the vehicle of transmission — United States**  **Class Epidemiologic data**  **Water-quality data**
I

II

III

IV Adequate Data provided about exposed and unexposed persons, with relative risk or odds ratio >2 or p-value <0.05

Adequate

Provided but limited

Epidemiologic data provided that did not meet the criteria for Class I, or claim made that ill persons had no exposures in common, besides water, but no data provided

Provided but limited Provided and adequate Laboratory data or historical information (e.g., the history that a chlorinator or pH acid feed pump malfunctioned, no detectable free-chlorine residual, or a breakdown in a recirculation system)

Not provided or inadequate (e.g., laboratory testing of water not

conducted and no historical information)

Provided and adequate

Not provided or inadequate

### 6 **MMWR September 12, 2008** 



# Results
Waterborne-Disease Outbreaks

Excluding Vibrioand PAM cases and aquatic facility-related health events, a total of 78 outbreaks (38 in 2005 and 40 in 2006) associated with recreational water were reported to CDC (Tables 2–5). This is the highest number of outbreaks reported for a 2-year summary since reporting began in 1978. Of the 50 states and 10 territories, localities, and FAS participatingin WBDOSS, 31 states reported WBDOs (Figure 2). Descriptions of selected WBDOs are presented in this report (Appendix B, Selected Descriptions of Waterborne Disease and Outbreaks [WBDOs] Associated with Recreational Water). These 78 outbreaks affected 4,412 persons andresulted in five deaths. The median outbreak size was 13 persons (range: 2–2,307 persons). Minnesota reported the highest number of WBDOs (nine), New York and Florida each reported seven WBDOs, and Wisconsin reported six WBDOs.

During 2005–2006, treated water venues were associated with 58 (74.4%) of the recreational water outbreaks and 4,167 (94.4%) of the cases (Tables 2 and 3; Figure 3). Untreated venues were associated with 20 (25.6%) of WBDOs but only 245 (5.6%) of the cases (Tables 4 and 5).

Of the 78 WBDOs, 48 (61.5%) were outbreaks of acute gastroenteritis illness (AGI), 11 (14.1%) were outbreaks of dermatitis or other skin conditions, and 11 (14.1%) were outbreaks of acute respiratory illness (ARI). The remaining WBDOs resulted in leptospirosis (n = two), PAM (n = one), and mixed or other illnesses (n = five) (Table 6, Figure 3). WBDOs associated withgastroenteritis accounted for 4,015 (91.0%) of the cases of illness. The route of entry implicated for each WBDO was ingestion for 48 outbreaks (61.5%), inhalation for 10 (12.8%), contact for 8 (10.3%), combined routes for nine (11.5%), and other ( Naegleria and Leptospira ) for three (3.8%) Figure 3). WBDOs occurred in every calendar month. However, the summer months (June through August) accounted for 51(65.4%) WBDOs and 3,890 (88.2%) cases (Figure 4). Gastroenteritis was particularly clustered during these months with 40/48 (83.3%) outbreaks and 3,777/4,015 (94.1%) cases being reported.

**TABLE 2. Waterborne-disease outbreaks (n = 24) associated with treated recreational water, by state — United States, 2005**
**No. of cases**

**State Month Class*** **Etiologic agent Predominant**  **illness †**  **(deaths) (n = 3,376)**  **Type Setting**  Connecticut Apr I Pseudomonas aeruginosa Skin 4 Pool, Spa Hotel Florida Jun II Cryptosporidium AGI 47 Pool Hotel Iowa Jun II Cryptosporidium AGI 24 Pool Community Kansas Jul II Cryptosporidium AGI 84 Pool Water park Kentucky Jun IV Cryptosporidium AGI 53 Pools Community Kentucky Jun IV Cryptosporidium AGI 9 Pool, wading pool Community Louisiana Aug IV Cryptosporidium AGI 31 Interactive fountain Water park Massachusetts Jul III Giardia intestinalis AGI 11 Pool Membership club Minnesota May II Unidentified AGI 32 Pool, spa Membership club Minnesota Aug IV Legionella pneumophila serogroup 1 ARI 3 Spa Private residence Minnesota Apr I Unidentified § ARI, eye 20 Pool, spa Hotel Minnesota Mar IV Unidentified ¶ Skin 8 Spa Hotel North Carolina Apr III L. pneumophila serogroup 1 ARI 4 (1) Spa Private residence New Mexico Apr III P. aeruginosa Skin, ear 7 Pool, spa Hotel New York Aug II Cryptosporidium AGI 97 Pool Camp New York Oct III Cryptosporidium AGI 22 Pool Membership club New York Jun I C. hominis ** AGI 2,307 Interactive fountain State park Ohio Jul III Chlorine gas †† ARI 19 Pool Community Ohio Aug III C. hominis AGI 523 Pools Community Oregon Jul II C. parvum AGI 20 Pool Membership club South Carolina Oct III L. pneumophila §§ ARI 18 Spa Hotel Vermont Feb IV Unidentified ¶ Skin 18 Spa Hotel Wisconsin Jul I P. aeruginosa Skin 9 Pool, Spa Hotel Wyoming Jul IV Campylobacter jejuni AGI 6 Kiddie pool Private residence * On the basis of epidemiologic and water-quality data provided on CDC form 52.12 (available at http://www.cdc.gov/healthyswimmi ng/downloads/

cdc_5212_waterborne.pdf) (see Table 1). † Skin: illness, condition, or symptom related to skin; AGI: acute gastrointestinal illness; ARI: acute respiratory illness; Eye: illness, condition, or symptom

related to eyes; and Ear: illness, condition, or symptom related to ears. § Etiology unidentified: contamination from excess chlorine levels or pool disinfection by-products (e.g., chloramines) suspected

. ¶ Etiology unidentified: P. aeruginosa suspected on the basis of clinical syndrome and setting. ** Species determined using molecular technology and current taxonomic guidelines ( **Source:** Xiao L, Ryan UM. 2008: Molecular epidemiology,

In: Cryptosporidium and cryptosporidiosis. Fayer R, Xiao L, eds. Boca Raton, Florida: CRC Press; 2008:119-71). †† Chlorine gas was released after high levels of liquid chlorine and acid were mixed in the recirculation system and subsequentlyreleased into the pool water. §§ Fifteen persons were diagnosed with Pontiac fever and three persons were diagnosed with Legionnaires' disease.

### 7 **Vol. 57 / SS-9 Surveillance Summaries** 

**TABLE 3. Waterborne-disease outbreaks (n = 34) associated with treated recreational water, by state — United States, 2006**
**No. of cases**
**State Month Class* Etiologic agent** **Predominant illness**  **† (deaths)**  **(n = 791) Type**  **Setting**
Arkansas Jul I Legionella pneumophila § ARI 37 Pool, spa Hotel California Jul II Shigella sonnei AGI 9 Kiddie pool Private residence California Jul III Cryptosporidium ¶ AGI 16 Interactive fountain Community Colorado Aug II Cryptosporidium** AGI 12 Pool Community Colorado Oct II L. pneumophila serogroup 1 †† ARI 6 Spa Private home Florida Jan I L. pneumophila serogroup 1 ARI 11 (1) Spa Hotel Florida May III Giardia, Cryptosporidium §§ AGI 55 Interactive fountain Community Florida Aug IV Cryptosporidium AGI 3 Pool Hotel Georgia Aug IV Cryptosporidium AGI 19 Pool Community Georgia Feb IV Unidentified ¶¶ Skin 4 Spa Cabin Georgia Oct IV Cryptosporidium AGI 4 Pool Community Illinois Jan I Legionella*** ARI 43 (1) Pool, spa Hotel Illinois Jul I C. hominis** AGI 65 Pool Day camp, water park Illinois Jun III Unidentified ††† Skin 9 Pool Community Illinois Aug IV Cryptosporidium AGI 4 Pool Water park Illinois Aug IV Cryptosporidium AGI 18 Pool Water park Indiana Apr IV Unidentified ARI, ear 12 Pool Membership club Kansas Dec IV Pseudomonas aeruginosa Skin 8 Spa Private residence Louisiana Jul II Cryptosporidium** AGI 29 Pool, interactive fountain Water park Minnesota Sep II C. hominis AGI 47 Pool Schools Missouri Jul IV Cryptosporidium AGI 6 Pool Community Missouri Jun III Cryptosporidium AGI 116 Pool, interactive fountain Water park Montana Jul IV Cryptosporidium AGI 82 Pools Community Nebraska Dec III Unidentified §§§ ¶¶¶ ARI, eye 24 Pool Hotel New York Oct III L. pneumophila serogroup 1 ARI 2 Spa Water park New York Mar IV Unidentified §§§ ARI 9 Pool Water park Pennsylvania Jun IV Cryptosporidium AGI 13 Pool Membership club South Carolina Jul III C. hominis** AGI 12 Pool Community Tennessee Mar IV Unidentified ¶¶ Skin 15 Pool, spa Hotel Wisconsin Feb III Unidentified ¶¶ Skin 28 Pool, spa Hotel Wisconsin May I Norovirus AGI 18 Pool Hotel Wisconsin Aug II Cryptosporidium AGI 22 Pool Campground Wisconsin Aug IV Cryptosporidium AGI 4 Pool Community Wyoming Jun II Cryptosporidium ** AGI 29 Pools**** Community * On the basis of epidemiologic and water-quality data provided on CDC form 52.12 (available at http://www.cdc.gov/healthyswimmi ng/downloads/

cdc_5212_waterborne.pdf) (see Table 1). † ARI: acute respiratory illness; AGI: acute gastrointestinal illness; Skin: illness, condition, or symptom related to skin; Ear: illness, condition, or

symptom related to ears; and Eye: illness, condition, or symptom related to eyes. § Pontiac fever was diagnosed in 34 persons, and Legionnaires’ disease was diagnosed in three persons. ¶ Eleven pulsed-field gel electrophoresis-matched cases of Salmonella stanley were also detected among persons who visited the fountain during this outbreak; however, the outbreak investigation did not rule out other possible common exposures among those case-pat ients. **** Source:** CDC. Cryptosporidiosis outbreaks associated with recreational water use — five states, 2006. MMWR 2007;56:729–32. †† All cases were diagnosed as Pontiac fever. §§ Thirty-five persons had stool specimens that tested positive for Giardia , seven persons had stool specimens that tested positive for Cryptosporidium, and two persons had stool specimens that tested positive for both Giardia and Cryptosporidium

. ¶¶ Etiology unidentified: Pseudomonas aeruginosa suspected on the basis of clinical syndrome and setting. *** Pontiac fever was diagnosed in 40 persons, and Legionnaires’ disease was diagnosed in three persons. L. pneumophila and L. maceachernii were detected in both pool and spa water. ††† Etiology unidentified: low pH suspected on the basis of water testing and symptoms. §§§ Etiology unidentified: chemical contamination from pool disinfection by-products (e.g., chloramines) suspected. ¶¶¶ **Source:** CDC. Ocular and respiratory illness associated with an indoor swimming pool—Nebraska, 2006. MMWR 2007;56:929–32.   Case-patients identified in this outbreak reported exposure to multiple community pools and to an untreated reservoir.



### Etiologic Agents parasites; 22 (28.2%), bacteria; four (5.1%), viruses; and two (2.6%), chemicals (Figure 3). Of the 78 WBDOs associated with recreational water, the Of the 47 outbreaks associated with treated water venues etiologic agent was confirmed in 62 (79.5%), suspected in 12 with an identified etiologic agent: 31 (66.0%) involved para­ (15.4%) and unidentified in four (5.1%) (Table 7). Thirty- sites; 14 (29.8%), bacteria; one (2.1%), a virus; and one (2.1%) four (43.6%) outbreaks were confirmed as being caused by

### 8 ** MMWR** **September 12, 2008**

**TABLE 4. Waterborne-disease outbreaks (n = 14) associated with untreated recreational water, by state — United States, 2005**
**No. of cases Predominant**  † **(deaths) State Month**  **Class* Etiologic agent** **illness (n = 171) Type**  **Setting** California Jul IV Unidentified § Skin 2 Lake Lake California Jul IV Leptospira Lep 3 Stream Stream Florida Jul I Unidentified ¶ Other 24 Ocean ¶ Beach Florida Nov II Leptospira Lep 43 Stream Adventure race Maine Jul III Unidentified AGI 10 Lake Swimming beach Massachusetts Jul IV Shigella sonnei AGI 5 Lake Lake Michigan Jun IV Copper sulfate ARI 3 Lake Lake Minnesota Jun IV Escherichia coli O157:H7 AGI 4 Lake Swimming beach Minnesota Jul IV S. sonnei AGI 12 Lake Swimming beach Minnesota Aug IV Norovirus AGI 8 Lake Swimming beach New York Jul III Cryptosporidium AGI 27 Lake Swimming beach New York Aug III Unidentified** AGI 13 Lake Lake Oklahoma Jul IV Naegleria fowleri Neuro 2 (2) Unknown †† Unknown Pennsylvania Jul IV S. sonnei AGI 15 Lake Swimming beach * On the basis of epidemiologic and water-quality data provided on CDC form 52.12 (available at http://www.cdc.gov/healthyswimmi ng/downloads/

cdc_5212_waterborne.pdf) (see Table 1). † Skin: illness, condition, or symptom related to skin; Lep: leptospirosis; Other: undefined or mixed illness, condition, or symptom. AGI: acute gastrointestinal illness; ARI: acute respiratory illness; Skin: illness, condition, or symptom related to skin; and Neuro: neurologic cond ition or symptoms (e.g. meningitis). § Etiology unidentified: clinical diagnosis of cercarial dermatitis (caused by avian schistosomes). ¶ Etiology unidentified: whereas certain swimmers had symptoms consistent with seabathers eruption (caused by jellyfish larvae), a majority of persons

affected in this outbreak experienced systemic, flu-like illnesses which might have been related to another etiology. Swimmers alternated between marine and chlorinated swimming venues. ** Etiology unidentified: Illness was most consistent with norovirus infection on the basis of clinical syndrome. †† Whereas an interactive fountain at a water park was a common exposure for both case-patients, other potentially shared and untreated recreational water

exposures could not be ruled out.

**TABLE 5. Waterborne-disease outbreaks (n = six) associated with untreated recreational water, by state — United States, 2006**
**Predominant No. of cases** **State Month Class* Etiologic agent** **illness †**  **(n = 74) Type**  **Setting** Florida May II Norovirus G2 AGI 50 Lake Swimming beach Massachusetts Aug III Cryptosporidium AGI 6 Pond Camp Minnesota May II Norovirus G1 AGI 10 Lake Private beach Ohio Aug IV Unidentified § Skin 2 Pond Pond Tennessee Jul IV Escherichia coli O157:H7 AGI 3 Lake Swimming beach Wisconsin Jun IV E. coli O157:H7 AGI 3 Lake State park * On the basis of epidemiologic and water-quality data provided on CDC form 52.12 (available at http://www.cdc.gov/healthyswimmi ng/downloads/

cdc_5212_waterborne.pdf) (and Table 1). † AGI: acute gastrointestinal illness; and Skin: illness, condition, or symptom related to skin. § Etiology unidentified: clinical diagnosis of cercarial dermatitis (caused by avian schistosomes).



### a chemical (Table 7). Parasites were responsible for approximately 20 times more cases than bacteria (3,784 versus 167). Of the 15 WBDOs associated with untreated water venues with an identified etiologic agent, eight (53.3%) involved bacteria; three (20.0%) parasites; three (20.0%) viruses; and one (6.7%) a chemical.
Parasites

Of the 48 outbreaks of gastroenteritis, 33 (68.8%) were parasitic in origin, including 31 (93.9%) caused by Cryptosporidium , one (3.0%) caused by Giardia intestinalis

, and one (3.0%) caused by both Cryptosporidiumand Giardia (Tables 2–7; Figure 5). Of the 13 gastroenteritis outbreaks associated with untreated water venues, only two (15.4%) were caused by parasites. Two cryptosporidiosis outbreaks occurred; one in an untreated lake and the other in an untreated pond, causing 27 and six cases of illness, respectively. In contrast,parasites were the most common causes of gastroenteritis outbreaks associated with treated water venues; Cryptosporidium was the most common parasitic agent, causing 29 (82.9%) ofthe 35 outbreaks of gastroenteritis. Thirty-one of these parasitic gastroenteritis outbreaks occurred in treated water venues, causing illness in 3,784 persons. Three of these outbreakseach caused over 100 (range: 116–2,307 persons) cases of illness. In June 2005, an outbreak caused by C. hoministransmitted through a New York spray park resulted in 2,307 cases, mostly among young children. In August 2005, a C. hominis outbreak spread through multiple Ohio pools and resulted

### 9 **Vol. 57 / SS-9 Surveillance Summaries** 



### in 523 cases; this outbreak subsequently was linked to an outbreak in an adjoining state (Kentucky). In June 2006, an outbreak caused by Cryptosporidium at a water park in Missouri caused gastroenteritis in 116 persons

The one additional parasitic outbreak was caused by Naegleria fowleriand led to the death of two persons in Oklahoma. Despite an investigation by local public health authorities, the location of suspected common exposure (i.e., exposure in which the two persons probably became ill at the same time and place) was not identified.
Bacteria

Eight reported gastroenteritis outbreaks of confirmed bacterial origin were reported (Figure 5), two of which were at treated water venues. An outbreak of Camp ylobacter jejuni occurred in a fill-and-drain pool at a Wyoming home in July 2005, resulting in five children and one adult becoming ill. This same type of pool was the setting for a Shigella sonnei outbreak at a California home in July 2006, leading to nine persons becoming ill, including three who were hospitalized. Both of these outbreaks were caused by a lack of disinfection and heavy use of these pools by young diaper-aged childr en. The other six outbreaks of gastroenteritis, caused by bacteria, were associated with swimming in lakes, including three additional shigellosis outbreaks and three outbreaks of E. coli O157:H7infection. All six lake-associated outbreaks occurred during June and July and five were associated with exposure to lake water during holidays or weekends.

Four of the bacterial outbreaks involved 28 cases of dermatitis caused by P seudomonas aeruginosa ; one of these outbreaks also resulted in ear infections. All four outbreaks of Pseudomonasinfection occurred at treated water venues that involved heated spa water (some of these outbreaks also involved pools). Five additional outbreaks were suspected to have been caused by Pseudomonas on the basis of the clinical symptoms and exposure to a spa.

Eight outbreaks caused by Legionella were associated with treated recreational water venues during 2005–2006, causing 124 cases of legionellosis (i.e., LD and PF) and resulted in three deaths. The largest **FIGURE 2. Number of recreational water-associated outbreaks (n = 78) — United States, 2005–2006** *

>4 (six states) 3 (three states) 2 (nine states) 1 (13 states) 0 (19 states)

* **Note:** These numbers are largely dependent on reporting and

surveillance activities in individual states and do not necessarily indicate the true incidence in a given state.

**FIGURE 3. Recreational water-associated outbreaks, by type of exposure, type of etiologic agent, predominant illness, and route of entry — United States, 2005–2006** 

Type of exposure (n = 78) Type of etiologic agent (n = 78)

Treated water Parasitic 74.4% 43.6%

Viral 5.1% Bacterial- Chemical/Toxin Legionella 10.3% 2.6%

Untreated Bacterial- Unidentified

water non- Legionella 17.9% 25.6% 20.5%

Predominant illness (n = 78)* Route of entry (n = 78)

AGI Ingestion 61.5% 61.5%

Other †
Mixed 6.4% 3.8% Combined Neuro 1.3% 3.8% Leptospirosis 2.6% Inhalation ARI Skin 14.1% 14.1% 14.1% Contact 15.4%

* AGI: acute gastrointestinal illness; ARI: acute respiratory illness; Skin: illness, condition or symptom

related to skin; Mixed: a combination of illnesses, conditions, or symptoms that might also include the eyes and ears; and Neuro: neurologic condition or symptoms (e.g., meningitis). † Infection with Naegleria was categorized as other because of the nasal, noninhalational route of

infection. Infection with Leptospira was categorized as other because the route of infection is typically through contact with mucous membrane or broken or abraded skin.

### 10 **MMWR September 12, 2008** 

**TABLE 6. Number of waterborne-disease outbreaks (n = 78) associated with recreational water, by predominant illness and type**  **of water — United States, 2005–2006 Type of water**  **Treated Untreated**  **Total**
**No. of No. of**  **No. of No. of**  **No. of No. of**  **Predominant illness outbreaks**  **cases outbreaks**  **cases outbreaks (%)**  **cases (%)**
AGI 35 3,849 13 166 **48 (61.5)**  **4,015 (91.0)**  ARI 10 152 1 3 **11 (14.1)**  **155 (3.5)**  Ear and Skin 1 7 0 0 **1 (1.3)**  **7 (0.2)**  Ear and ARI 1 12 0 0 **1 (1.3)**  **12 (0.3)**  Eye and ARI 2 44 0 0 **2 (2.6)**  **44 (1.0)**  Leptospirosis 0 0 2 46 **2 (2.6)**  **46 (1.0)**  Neuro 0 0 1 2 **1 (1.3)**  **2 (0.0)**  Skin 9 103 2 4 **11 (14.1)**  **107 (2.4)**  Other 0 0 1 24 **1 (1.3)**  **24 (0.5)**  **Total (%) 58 (74.4)**  **4,167 (94.4) 20 (25.6)**  **245 (5.6) 78 (100.0)**  **4,412 (100.0)** * AGI: acute gastrointestinal illness; ARI: acute respiratory illness; Ear: illness, condition, or symptom related to ears; Skin: illness, condition, or symptom

related to skin; Eye: illness, condition, or symptom related to eyes;. Neuro: neurologic condition or symptoms (e.g. meningitis); and Other: etiology unidentified. Whereas certain swimmers had symptoms consistent with seabathers eruption (caused by jellyfish larvae), the major ity of persons affected in this outbreak experienced systemic, flu-like illnesses which might have been related to another etiology. Swimmers alternated between marine and chlorinated swimming venues.

**FIGURE 4. Number of recreational water-associated outbreaks** **(n = 78), by predominant illness* and month — United States,** **2005–2006**

25

20

15

10

5

0 Leptospirosis
Mixed
Neuro
ARI
Skin
AGI

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
* Mixed: a combination of illnesses, conditions or symptoms that also

might include the eyes and ears; Neuro: neurologic condition or symptoms (e.g., meningitis); ARI: acute respiratory illness; Skin: illness, condition, or symptom related to skin; AGI: acute gastrointestinal illness.



### of these outbreaks was linked to a spa at an Illinois hotel and involved 43 persons, including three cases of LD resulting in one death. The environmental investigation documented inadequate disinfection in the spa and isolated both L. pneumophilaand L. maceachernii from the spa water. Two outbreaks in untreated recreational water were caused by Leptospira . Leptospirosis was diagnosed in 43 persons who participated in an adventure race in Florida in November 2005. A July 2005 outbreak of leptospirosis in California involved three persons who had contact with water from a low flowing stream at the time of exposure Viruses Four outbreaks of confirmed viral origin occurred, all of which caused gastroenteritis. Norovirus was identified as the etiologic agent in each of the outbreaks; three occurred at lakeswimming beaches, and one occurred in a treated water setting. These four norovirus outbreaks resulted in 86 cases of gastroenteritis. For the two outbreaks where lake water fecal indicator testing was conducted; no water quality-violations were documented. The water might have been contaminatedby ill swimmers at the time of exposure rather than by ongoing point source water contamination. The treated venue outbreak occurred in a hotel pool and was related to inadequatedisinfection and continued use by ill swimmers. One additional outbreak that was suspected to have been caused by norovirus resulted in 13 cases.
Chemicals

During 2005–2006, two outbreaks associated with chemicals involved 22 persons. In June 2005, a chemical-associated outbreak occurred in a Michigan lake causing respiratory symptoms in three swimmers. This outbreak was attributed to the unapproved addition of excessive amounts of copper sulfate to the lake water for aquatic nuisance control.

The other outbreak occurred in a treated water venue. In July 2005, the recirculation pump at a community pool was shut down for maintenance; however, the liquid chlorine (i.e., NaOCl) and muriatic (i.e., hydrochloric) acid continued to feed into the system and probably released chlorine gas in the piping. When the pump was restarted, a concentrated bolus of these swimming pool chemicals and chlorine gas was sent into a small pool where it caused respiratory distress in 19**TABLE 7. Number of waterborne-disease outbreaks (n = 78) associated with recreational water, by etiologic agent(s) and type of**  **water — United States, 2005–2006 Type of water**  **Total Treated**  **Untreated**

**Predominant illness No. of**  **outbreaks No. of**  **No. of cases outbreaks**  **No. of**

**cases No. of**  **outbreaks (%) No. of**  **cases (%)**
**Bacteria 14**  Campylobacter jejuni 1 Escherichia coli spp. 0 Leptospira spp. 0 Legionella spp.* 8 Pseudomonas aeruginosa 4 Shigella sonnei 1 **Parasites 31**  Cryptosporidium spp. 29 Giardia intestinalis 1 Naegleria fowleri 0 Cryptosporidium and Giardia spp. † 1 **Viruses 1** 

Norovirus 1 **Chemicals/toxins 1** 

Copper sulfate 0 Chlorine gas § 1 **Suspected etiology 9** 

Suspected chemical exposure ¶ 1 Suspected chloramines 3 Suspected norovirus 0 Suspected P. aeruginosa 5 Suspected schistosomes 0 **Unidentified 2**  **Total (%) 58 (74.4)**  **167** 6 0 0 124 2 8

9 **3,784** 3,718 1 1 0 5 5 **18** 18 **19**

0 1 9 **135**

9 53

0 7 3

0
**44 4,167 (94.4)**  **8** 0 3 2 0 0 3 **3** 2 0 1 0 **3** 3
**1** 1 0 **3** 0 0 1 0 2
**2 20 (25.6)**  **88** 0 10 46

0 0 3 2 **35** 33

0 2 0 **68** 68

**3** 3 0
**17**

0 0 13 0 4 **34 245 (5.6)**  **22 (28.2) 1**  **3 2**  **8 4**  **4 34 (43.6)**  **31**

**1 1**  **1 4 (5.1)**  **4 2 (2.6)**  **1 1**  **12 (15.4)**

**1 3**  **1 5**  **2 4 (5.1)**  **78 (100.0) 255 (5.8)**  **6 1**  **0 4**  **6 124** 

**2 8**  **4 1**  **3,819 (86.6) 3,751**  **1 1** 

**2 5**  **5 86 (1.9)**  **8 6**  **22 (0.5)**

**3 1**  **9 152 (3.4)** 

**9 5**  **3 1**  **3 7**  **3**

**4 78 (1.8)**  **4,412 (100.0)** 

### 11 **Vol. 57 / SS-9 Surveillance Summaries** 

* Five outbreaks were attributed to Legionella pneumophila , two outbreak investigations did not identify a Legionella species, and one outbreak investigation detected L. pneumophila and L. maceachernii in both pool and spa water. † Thirty-five persons had stool specimens that tested positive for Giardia , seven persons had stool specimens that tested positive for Cryptosporidium, and two persons had stool specimens that tested positive for both Giardia and Cryptosporidium

. § Chlorine gas was released after high levels of liquid chlorine and acid were mixed in the recirculation system and subsequently released into the pool

water. ¶ Low pH suspected on the basis of water testing and symptoms.



### persons. Three additional outbreaks in treated venues were suspected of being caused by disinfection by-products (e.g., chloramines) on the basis of symptoms and settings (i.e., indoor pool). Suspected Agents

Twelve outbreaks were reported in which no etiologic agentwas confirmed; however, investigation reports indicated a suspected agent on the basis of symptoms, type of water, setting,and background information (Table 7). Five of these 12 outbreaks were suspected to be caused by P. aeruginosa in treated spas. One outbreak, which caused rashes in nine children, was suspected of being caused by low pH. Three chemical-related outbreaks were suspected to be associated with exposure to excess chloramines (i.e., disinfection by-products of chlorination) ( 20–22 ) in the indoor pools and surrounding areas (i.e., indoor pool air), which resulted in ARI, and eye irritation. Norovirus was the suspected pathogen in one gastroenteritis outbreak associated with a lake on the basis of epidemiologic and clinical evidence. Two outbreaks were suspected to be the result of contact with avian schistosomes, causing cercarial dermatitis Unidentified Etiologic Agents

Data collected during investigations of four outbreaks ofunidentified etiology were not sufficient to suggest an etiologic agent. Gastroenteritis was reported as the predominant illness in two of these outbreaks, and ARI and ear infections were reported for the third one. The AGI outbreak in a treated venue (Minnesota 2005) caused illness in 32 persons over the course of nearly a month; 15 persons reportedly continued to swim while ill. Stool samples tested negative for bacteria,viruses, and parasites. A lake-associated AGI outbreak sickened 10 persons and caused five hospitalizations. Environmental testing revealed water-quality violations (e.g., elevated E. coli levels). An outbreak of ARI and ear infections among lifeguards occurred in a pool that had not officially opened for the season. The water was reportedly cloudy and possibly contaminated by water leaking from a pipe in the facility.

### 12 **MMWR September 12, 2008** 



### Finally, an outbreak of influenza-like illness linked to an ocean beach was associated with marine and pool water; possible etiologies might include contact with jellyfish larvae and other etiologies may have contributed to some of these illnesses.


## Single Cases of Waterborne Disease

Vibriosis Cases Associated with Recreational Water

During 2005–2006, a total of 189 vibriosis cases associated with recreational water use or exposure to flood water were reported from 20 states; representing 14.7% (189/1287) of the total number of vibriosis cases reported in 2005–2006 (62). Eighty-five (45.0%) of 189 patients were hospitalized, and 18 (9.5%) died (Table 8).

The most frequently isolated Vibriospecies was Vibrio vulnificus , which was isolated from 67 (35.4%) persons; 52 (77.6%) were hospitalized, and 15 (22.4%) died. V. alginolyticus was isolated from 60 (31.7%) persons; seven (11.7%) were hospitalized, and none died. V. parahaemolyticus was isolated from 33 (17.5%) persons; 12 (36.4%) were hospitalized, and one (3.0%) died. Other Vibrio species (including V. cholerae non-O1, non-O139, V. damsela

, V. fluvialis

, V. hollisae

, V. mimicus
, V. alginolyticus/parahaemolyticuscoinfection, V. alginolyticus/fluvialis coinfection, V. parahaemolyticus/ vulnificus coinfection, V. vulnificus /unidentified Vibriospecies coinfection and Vibrio species not identified) were identified in

**FIGURE 5. Recreational water-associated outbreaks of gastroenteritis, by type of exposure and etiologic agent — United States, 2005–2006** 

Etiologic agent: untreated water (n = 13) Etiologic agent: treated water (n = 35)*

S. sonnei 23.1%

Norovirus 23.1% E. coli O157:H7 23.1%

Unidentified

15.4% Cryptosporidium spp. 82.8% Etiologic agent (n = 48)

Cryptosporidium spp. 64.6% Escherichia coli O157:H7 6.3% Type of exposure (n = 48)*

Untreated water 27.1% Treated water 72.9%

Campylobacter spp. 2.9% 2.9%

9 9 Norovirus 2.9%

Unidentified 2.9%

2. %

and spp. 2. % S. sonnei G. intestinalis Cryptosporidium Giardia

Cryptosporidium spp. 15.4% spp. 2.1% Campylobacter

Cryptosporidium Giardia spp. 2.1% and Unidentified 6.3%

Norovirus 8.3% G. intestinalis 2.1%
Shigella sonnei 8.5%

* For one outbreak (Wyoming 2006) case-patients reported exposure to multiple community pools

and to a reservoir. This outbreak is being analyzed as exposure to treated water. 

### 29 (15.3%) persons; 14 (48.3%) were hospitalized, and two (6.9%) died.

Geographic location. Nearly all Vibriopatients reported that they were exposed to recreational water in a coastal state (Figure 6). The most frequently reported location was the Gulf Coast (61.9%); Atlantic Coast states, excluding Florida (19.6%); Pacific Coast states (16.9%); and inland states (1.6%)(Table 9). Florida and Mississippi reported the highest number of cases, 55 and 28 cases, respectively (Figure 6; Table 9).

Seasonality. The temporal distribution of illness in patients from whom Vibriospecies were isolated displayed a clear seasonal peak during the summer (Figure 7). The greatest frequency of Vibrio cases occurred during July through September.

Exposures. Activities associated with Vibriocases included swimming, diving, or wading in water (70.9%); walking or falling on the shore or rocks (32.8%); and boating, skiing, or surfing (19.6%). Twenty-five case-patients reported exposure to Hurricane Katrina flood waters.

Signs/Symptoms. Symptoms associated with Vibrioillnesses included cellulitis (56.6%), fever (36.0%), muscle pain (21.2%), bullae (15.9%), ear infections (14.3%), nausea (13.8%), and shock (10.1%). V. vulnificus accounted for the majority of skin infections (e.g., cellulitis, bullae), causing 70 (50.7%) of 138. V. vulnificus also accounted for the majorityof severe illnesses, including those with fever (51.5%), bacteremia (75.0%), shock (73.7%), and amputations (83.3%). V. alginolyticus accounted for the majority of ear infections (24 [92.3%] of 26). Other symptoms and infections were reported in low frequencies (e.g., bladder infections, hematuria, eye infections, respiratory symptoms, sinus infections, diarrhea, and vomiting). Naegleria Infections

In addition to the outbreak of PAM (two cases), three individual fatal cases of PAM caused by N. fowleriwere reported in 2005–2006 (Table 10). A child in Texas died in September 2005, 13 days after swimming in a lake. In August 2006, a child died of PAM associated with N. fowleriafter swimming, using a personal watercraft, and tubing in an Arizona lake. In August 2006, a child died after swimming in a Georgia pond.**TABLE 8. Number of illnesses associated with Vibrio**  **isolation (n = 189) and recreational water, by species and year — United**  **States, 2005–2006**
**Year Total**  **2005 2006**  **Species Cases**  **Hospitalizations Deaths**  **Cases Hospitalizations**  **Deaths Cases**  **Hospitalizations Deaths**  Vibrio alginolyticus V. cholerae non-O1, non-O139 V. damsela V. fluvialis V. hollisae V. mimicus V. parahaemolyticus V. vulnificus Multiple* Vibrio , species not identified **Total (% of cases) Percentage by year**  31 4 2 2 1 0 21 50

3 4 **118 (62.4)**  6 2 0 2 0 0 8 41

3 3 **65 (55.1%) (76.5)**  0 0 0 1 0 0 1 11

1 0 **14 (11.9%) (77.8)**  29 4 0 1 0 1 12 17 2 5
**71 (37.6)**  1 1 0 0 0 0 4 11

1 2 **20 (28.2%) (23.5)**  0 0 0 0 0 0 0 4 0 0 **4 (5.6%) (22.2)**  **60 8**  **2 3**  **1 1**  **33 67** 

**5 9**  **189 (100)**  **7 0 3 0**  **0 0 2 1**  **0 0 0 0**  **12 1 52 15** 

**4 1 5 0**  **85 (45.0%) 18 (9.5%)**

**(100) (100)** 

### 13 **Vol. 57 / SS-9 Surveillance Summaries** 

* Includes V. alginolyticus /parahaemolyticus coinfection, V. alginolyticus /fluvialis coinfection, V. parahaemolyticus/vulnificus coinfection , V. vulnificus/ unidentified, and Vibrio species coinfection.


### Previously Unreported Outbreaks

Thirty-one previously unreported recreational water-associated outbreaks and one case of waterborne disease during 1978– 2004 were received and entered into WBDO database (Table 11). These outbreaks were summarized but not included in analysis for this report. One outbreak of leptospirosis in Hawaii was associated with exposure to flood water ( 48).Reports on the remaining 30 events were received from Minnesota, New York, and Tennessee. These states participate in the Environmental Health Specialist Network Water program(EHS-Net Water), which is an EPA and CDC funded initiative that supports a waterborne-disease environmental health specialist in each site. These three sites identified outbreaks and case reports that were previously unreported to CDC and reported them as part of a retrospective review of waterborne disease outbreaks in these states. The 31 previously unreported outbreaks affected 673 persons; 25 (80.6%) of the outbreaks occurred in treated water venues.


## Surveillance Reports Not Classified as Waterborne Disease and Outbreaks

One report from New Hampshire was not included in this summary. In February 2005, three children had lesions believed to be caused by Molluscum contagiosum . These children all swam at the same community pool; however, afterinvestigation, it was not clear that these lesions were associated with waterborne transmission of this organism versusother modes of transmission (e.g., person to person or contact with contaminated towels or objects). **FIGURE 6. Number* of illnesses associated with** **Vibrio isolation**  **and recreational water (n = 189) — United States, 2005–2006**

>10 (six states) 5–9 (four states) 2–4 (five states) 1 (five states) 0 (30 states)

* **Note:** These numbers are largely dependent on reporting and

surveillance activities in individual states and do not necessarily indicate the true incidence in a given state.



### Aquatic Facility-related Health Events not Associated with Recreational Water

Thirty-two reports of nonwater related health events that occurred during 1983–2006 and were associated with aquatic facilities were reported by New York (Table 12). Although they are not counted as waterborne-disease cases or outbreaks for analysis purposes, they are included in this report because they illustrate important lessons about pool maintenance and operation. Most of these events, 90.6% (29/32), were caused by improper use of chemicals; incompatible pool chemicals (e.g., acid and bleach) were mixed, which resulted in the release of chlorine gas. Persons at these aquatic facilities expe­

### 14 **MMWR September 12, 2008** 

**TABLE 9. Number of recreational water-associated Vibrio**  **isolations (n = 189) and deaths (n = 18), by region/state and species — United States, 2005–2006**  **Species**
**Total V. alginolyticus**  **V. parahaemolyticus V. vulnificus**  **Other/unknown species*** **Region/State †**  **Cases Deaths Cases Deaths**  **Cases Deaths Cases Deaths**  **Cases Deaths**

**Atlantic**

Connecticut Georgia Maine Maryland North Carolina New Jersey New York South Carolina Virginia
**Total Gulf Coast**  **§** Alabama Florida ¶ Louisiana Mississippi Texas
**Total**
**Noncoastal**

Illinois Kansas Minnesota
**Total Pacific**  California Hawaii Oregon
**Total**
**Total Percentage**  1 0 2 2 2 1 1 3 2
**14**

0 19

1 0 3
**23**

0 0 0
**0**

7 15

1
**23**
**60 (31.7)**  0 0 0 0 0 0 0 0 0
**0**

0 0 0 0 0
**0**

0 0 0
**0**

0 0 0
**0**
**0 (0)**  2 0 0 2 2 4 0 0 2
**12**

1 9 0 6 4
**20**

0 0 0
**0**

0 1 0
**1**
**33 (17.5)**  0 0 0 0 0 0 0 0 0
**0**

0 0 0 1 0
**1**

0 0 0
**0**

0 0 0
**0**
**1 (5.6)**  0 1 0 2 3 0 0 0 0
**6**

0 16 19 18 3
**56**

0 0 0
**0**

1 4 0
**5**
**67 (35.4)**  0 0 0 0 1 0 0 0 0
**1**

0 1 5 6 0
**12**

0 0 0
**0**

0 2 0
**2**
**15 (83.3)**  0 0 0 0 1 1 1 0 2
**5**

1 11

1 4 1
**18**

1 1 1
**3**

2 1 0
**3**
**29 (15.3)**  0 0 0 0 0 0 0 0 0
**0**

0 1 0 1 0
**2**

0 0 0
**0**

0 0 0
**0**
**2 (11.1)**  **3 1**  **2 6**  **8 6**  **2 3**  **6**
**37**

**2 55**  **21 28**  **11**
**117**

**1 1**  **1**
**3**

**10 21** 

**1**
**32**
**189 (100)**  **0 0**  **0 0**  **1 0**  **0 0**  **0**
**1**

**0 2**  **5 8**  **0**
**15**

**0 0**  **0**
**0**

**0 2**  **0**
**2**
**18 (100)**  * Includes V. cholerae (non-O1, non-O139 ), V. damsela

, V. fluvialis

, V. hollisae, V. mimicus, V. alginolyticus /parahaemolyticus coinfection, V. alginolyticus / fluvialis coinfection, V. parahaemolyticus/vulnificus coinfection , V. vulnificus/ unidentified Vibrio species coinfection, and Vibrio species not identified. † Refers to the reported state of exposure if the exposure did not occur in the reporting state. § Includes 25 cases with reported exposure to Hurricane Katrina flood waters. ¶ Nine reports from Florida indicate Atlantic coast exposure.



### rienced respiratory distress. Two additional events were caused by carbon monoxide in indoor pools, and one event was caused by liquid chlorine splashing into the eye of an aquatic facility employee.



# Discussion Trends in Reporting Outbreaks

A total of 78 recreational water–associated WBDOs were reported to CDC during 2005–2006. This represents an increase from the 2003–2004 Surveillance Summary (n = 62) and is the largest number of outbreaks ever reported in a2-year period (Figure 8). Overall, the number of reported recreational water-associated WBDOs reported annually have increased substantially since 1978, when CDC first began receiving these reports (Figure 8). These increases probably are a result of a combination of factors, such as the emergence of pathogens (e.g., Cryptosporidium ), increased participation in aquatic activities, and increases in the number of aquatic venues. Increased recognition, investigation, and reporting ofrecreational water-associated outbreaks also might be contributing factors.

An unprecedented number of states reported outbreaks during 2005–2006, and WBDOs demonstrate geographic variation (Figure 2). Differences in reporting between states might be attributable to several factors, including ability to detect outbreaks, availability of laboratory testing, variable requirements for notifiable diseases, and the surveillance and investigation capacity of individual state and local public health

### 15 **Vol. 57 / SS-9 Surveillance Summaries** 

**FIGURE 7. Number of illnesses associated with Vibrio**  **isolation and recreational water (n = 189), by species and month —**  **United States, 2005–2006**

50
Other species* (n = 29) V. parahaemolyticus (n = 33) 40 V. alginolyticus (n = 60)
V. vulnificus (n = 67) 30

20

10

0

Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

* Includes V. cholerae (non-O1, non-O139) (eight), V. damsela (two),

V.

fluvialis (three), V. hollisae (one), V. mimicus (one), V. alginolyticus/ parahaemolyticus coinfection (one), V. alginolyticus/fluvialis coinfection (one), V. parahaemolyticus/vulnificus coinfection (two), V. vulnificus / unidentified Vibrio species coinfection (one), and Vibrio species not identified (nine).



### agencies. These differences in the ability to detect, investigate,and report WBDOs probably lead to reporting and surveillance bias. Therefore, the states with the majority of outbreaks reported for this period might not be the states in which the majority of outbreaks actually occurred. An increase or decrease in the number of WBDOs reported might reflect either an actual change in the incidence of outbreaks or a change in the sensitivity of surveillance systems.

Etiologic agents with shorter incubation periods might bemore easily linked to water exposures, facilitating the recognition of outbreaks. Additional factors that might influence which WBDOs are reported include the size and location ofthe outbreak, severity of illness, and the geographic dispersion of ill persons. Larger outbreaks are more likely to be identified by public health authorities. In contrast, smaller outbreaks (e.g., those associated with private residential pools and spas) might go undetected because fewer persons are ill, and they might attribute illness to other common exposures. In addition, outbreaks of gastroenteritis associated with large venues that draw from a wide geographic range (e.g., large lakes and marine beaches) might be difficult to detect because potentially infected persons disperse widely from the site of exposure and, therefore, might be less likely to be identified as part of an outbreak. P rospective epidemiology studies, such as the EPA’s NEEAR Water Study ( 18), have revealed elevatedrates of gastroenteritis in swimmers compared with nonswimmers on all beaches studied. Multiple other prospective studies of gastroenteritis associated with beach swimming havealso indicated elevated rates of illness associated with swimming in lakes and oceans, though few outbreaks have been detected (23,24). Consistent with this finding, no oceanassociated outbreaks and only one Great Lakes-associated outbreak of gastroenteritis has been reported since 1978 ( 12 ). These endemic recreational water-associated illnesses are not capturedby WBDOSS, supporting the need for more studies to estimate the magnitude of risk for illness for routine, nonoutbreakassociated exposures at recreational water venues.

WBDOs associated with recreational water use occur yearround, but the numbers of reported WBDOs and cases are highest during the annual summer swim season (Figure 4).For public health professionals and swimming venue operators, the seasonality of waterborne-disease outbreaks can help determine the allocation of resources so that health education messages are targeted to populations during times of the year when the risk for preventable illness is highest.


## Swimming Pools

Swimming pools are designed to be chemically treated and filtered to reduce the risk for illness associated with exposure to infectious pathogens. Despite the availability of thesedisinfection measures, pools remain susceptible to contamination because of chlorine-resistant organisms (i.e., Cryptosporidium ) or inadequate treatment resulting from poor operation or maintenance. In addition, an emerging focus of concern at swimming pools is the risk for chemical injury from improper handling of pool chemicals.
Infectious Gastroenteritis

Approximately 87% of all cases reported to WBDOSS during 2005–2006 were involved in infectious gastroenteritis outbreaks associated with treated recreational water venues.

**TABLE 10. Single cases of non- Vibrio**  *** waterborne disease (n = 3) associated with untreated recreational water, by state — United States, 2005–2006** 
**Predominant No. of cases**  **State Date**  **Etiologic agent illness**  † **(deaths) (n = 3 ) Type**  **Setting**
Arizona Aug 2006 Naegleria fowleri Neuro 1 (1) Lake Lake Georgia Aug 2006 N. fowleri Neuro 1 (1) Pond Pond Texas Sep 2005 N. fowleri Neuro 1 (1) Lake Lake * In addition to these single cases, 189 cases of recreational water-associated Vibrio infection were reported: 118 cases in 2005 and 71 cases in 2006. † Neuro: neurologic condition or symptoms (e.g., meningitis).**TABLE 11. Waterborne disease (n = 1) and outbreaks (n = 31) associated with recreational water that were not included in previous**  **Surveillance Summaries**  **, by state — United States, 1978–2004**
**Predominant No. of cases State**  **Date Class* Etiologic agent** **illness †**  **(n = 673) Type Setting** 
**Disease**

New York Jul 1992 NA Unidentified § Eye 1 Pool Hotel **Outbreak**

Hawaii Nov 2004 IV Leptospira interrogans ¶ Lep 2 Stream University Minnesota Jul 1992 III Unidentified** Skin 6 Pool Hotel Minnesota Jan 1998 III Giardia intestinalis AGI 7 Pool Hotel Minnesota Apr 1998 II Unidentified** Ear, eye, skin 17 Pool Community Minnesota May 1998 III Unidentified** Skin 22 Pool Community Minnesota Jul 1998 IV Norovirus †† AGI 15 Lake Swimming beach Minnesota Jul 2000 I Legionella §§ ARI 51 Pool, spa Hotel New York Oct 1978 IV P. aeruginosa Skin 2 Spa Hotel New York Aug 1981 IV Leptospira Lep 6 Stream Swimming area New York Aug 1988 III Chlorine gas ¶¶ AGI, ARI 21 Pool Community New York Mar 1989 III Unidentified § ARI, skin 3 Pool Hotel New York Jul 1989 III Chlorine gas ¶¶ ARI 11 Pool College New York Jun 1990 III Chlorine gas ¶¶ ARI 15 Pool School New York Mar 1992 III P. aeruginosa Skin 34 Spa Resort New York May 1992 III P. aeruginosa Skin 6 Pool, spa Hotel New York Oct 1992 III Unidentified*** Eye, skin, other 20 Pool School New York Nov 1994 III Unidentified § AGI, ARI, eye, skin 51 Pool School New York Mar 1995 III Chlorine gas ¶¶ ARI 5 Pool Membership club New York Nov 1995 III P. aeruginosa Skin 13 Pool Hotel New York Dec 1995 III P. aeruginosa Skin 3 Pool School New York Jan 1996 IV Unidentified ††† ARI, skin 29 Pool, spa Hotel New York Mar 1997 III P. aeruginosa Skin 10 Pool Hotel New York Mar 1997 IV Unidentified** Skin 19 Pool Hotel New York Sep 1997 III Chloramines ARI, eye, skin 51 Pool School New York Sep 1998 III Hydrochloric acid ARI 3 Pool School New York Jan 1999 III Unidentified § Eye, skin 2 Pool School New York Jun 1999 III Unidentified §§§ AGI 140 Lake Swimming beach New York Mar 2000 III Unidentified § Eye 2 Pool Hotel New York Feb 2001 I Chlorine ¶¶¶ Skin 58 Pool, spa Hotel New York Jul 2002 III Shigella sonnei AGI 20 Lake Swimming beach Tennessee Jun 1997 II Cryptosporidium AGI 28 Lake Swimming beach 

### 16 **MMWR September 12, 2008** 

* On the basis of epidemiologic and water-quality data provided on CDC form 52.12 (available at http://www.cdc.gov/healthyswimmi ng/downloads/

cdc_5212_waterborne.pdf). NA: Single cases of waterborne disease are not classified (see Table 1). † Eye: illness, condition, or symptom related to eyes; Lep: leptospirosis; Skin: illness, condition, or symptom related to skin; AGI: acute gastrointestinal

illness; Ear: illness, condition, or symptom related to ears; ARI: acute respiratory illness; and Other: undefined illness, condition, or symptom. § Etiology unidentified: chemical contamination from excess chlorine levels or pool disinfection by-products (e.g., chloramines) suspected. ¶ **Source** : Gaynor K, Katz AR, Park SY, Nakata M, Clark TA, Effler PV. Leptospirosis on Oahu: an outbreak associated with flooding of a u niversity

campus. Am J Trop Med Hyg 2007;76:882–5. ** Etiology unidentified: P. aeruginosa suspected on the basis of clinical syndrome and setting. †† Four persons had stool specimens that tested positive for norovirus, and three persons had stool specimens that tested positive for Staphylococcus aureus

. §§ All cases were diagnosed as Pontiac fever (PF). ¶¶ Chlorine gas was released after high levels of liquid chlorine and acid were mixed in the recirculation system and subsequently released into the pool

water. *** Etiology unidentified: high chlorine levels, disinfection by-products, and low pH suspected on the basis of clinical syndrome and setting. In addition to burning eyes and irritated skin, swimmers experienced teeth staining and loss of body hair. ††† Etiology unidentified: Legionella and P. aeruginosa suspected on the basis of clinical syndrome (PF and rash) and setting. §§§ Etiology unidentified: norovirus suspected on the basis of clinical syndrome. ¶¶¶ Injuries occurred after the hand-addition of chlorine into a pool while swimmers were using it.



### Two outbreaks were caused by chlorine-sensitive agents no documented response existed that indicated that chlorine ( Giardiain Massachusetts, July 2005, and norovirus in was added or that the pool was closed. Previous outbreak Wisconsin, May 2006) and might have been prevented or investigations have demonstrated that the implementation of reduced in scale by proper aquatic monitoring, maintenance, appropriate pool operation practices (e.g., adequate disinfecand/or operation practices. Investigation of the Massachusetts tion) effectively stops the transmission of chlorine-sensitive giardiasis outbreak revealed that although the chlorine levels pathogens (25 ). recorded on the pool log were below the recommended level,**TABLE 12. Other aquatic facility-related health events* (n = 32) not associated with recreational water use — New York, 1983–20** **06**
**Predominant No. of cases State**  **Date Etiologic agent**  **illness †**  **(n = 364 ) Type**  **Setting**
New York Mar 1983 Chlorine gas § ARI 3 Pool Housing complex New York Aug 1983 Chlorine gas § ARI 1 Pool Housing complex New York May 1984 Chlorine gas ¶ ARI 8 Pool College New York Jun 1987 Chlorine gas § ARI 6 Pool Community New York Aug 1987 Chlorine gas § ARI 41 Pool Membership club New York Aug 1988 Chlorine gas § ARI 10 Pool Membership club New York Oct 1988 Chlorine gas § ARI 1 Pool School New York Dec 1988 Chlorine gas § ARI, eye 29 Pool Institution New York Feb 1989 Chlorine gas § ARI 6 Pool School New York Jul 1989 Chlorine gas ¶ ARI 1 Pool Community New York Jul 1989 Chlorine gas § ARI 1 Pool Hotel New York Jul 1991 Chlorine gas § ARI 5 Pool School New York Jan 1992 Chlorine gas § ARI 2 Pool Membership club New York Jun 1992 Chlorine gas § ARI, eye 2 Pool School New York Feb 1993 Carbon monoxide suspected AGI, ARI 18 Pool School New York Sep 1993 Chlorine gas § ARI 3 Pool Membership club New York Jun 1994 Chlorine gas § ARI 1 Pool Membership club New York Jun 1994 Chlorine gas § ARI 1 Pool Institution New York Jun 1995 Chlorine gas § ARI 48 Pool School New York Oct 1995 Chlorine gas § ARI 91 Pool School New York Jul 1996 Chlorine gas § ARI 1 Pool Membership club New York Apr 1997 Chlorine gas § ARI 14 Pool School New York Jun 1997 Chlorine gas § ARI 15 Pool Membership club New York Aug 1997 Chlorine gas § ARI 18 Pool School New York Dec 1997 Chlorine gas § ARI 17 Pool Membership club New York Jul 1998 Chlorine liquid Eye 1 Pool Hotel New York Feb 2000 Carbon monoxide ARI 4 Pool Hotel New York Jan 2001 Chlorine gas § ARI 1 Pool School New York Jun 2002 Chlorine gas § ARI 1 Pool Housing complex New York Apr 2005 Chlorine gas § ARI 9 Pool Membership club New York Jul 2006 Chlorine gas § ARI 1 Pool Community New York May 2006 Chlorine gas § ARI 4 Pool Community 

### 17 **Vol. 57 / SS-9 Surveillance Summaries** 

* These events are not considered waterborne outbreaks because the vehicle of transmission was not water. † AGI: acute gastrointestinal illness; ARI: acute respiratory illness; and Eye: illness, condition or symptom related to eyes. § Chlorine gas was generated after inappropriate chemical preparation or mixing (e.g., liquid chlorine bleach and acid). ¶ Chlorine gas that was used to disinfect pool water was released, causing injury.



### During 2005–2006, Cryptosporidium spp. caused 31 recreational water–associated outbreaks, which involved 3,751 persons; 99.1% of these cases were associated with treated water venues. The number of the cryptosporidiosis outbreaks reported annually has substantially increased from nine in 1997–1998 to 31 in 2005–2006 (Table 7). This increase is particularly noticeable in the proportion of AGI outbreaks associated with Cryptosporidium in treated recreational water venues (Figures 5 and 9). These increases contribute to the observed increases in the total number of recreational water–associated outbreaks and, more specifically, outbreaks of gastroenteritis. Concurrently, cases of cryptosporidiosis reported to CDC have nearly doubled since 2004 (26 ). Although thereasons for increased cryptosporidiosis case and outbreak reporting are not completely understood, outbreaks associatedwith treated recreational water venues continue to be an important means of transmitting Cryptosporidium

. During 1997–2006, Cryptosporidium was infrequently attributed to outbreaks associated with lakes and rivers (12.7%of outbreaks), although it caused 68.3% of outbreaks associated with treated venues (Figure 9). This observation is consistent with the finding that Cryptosporidiumrequires extendedcontact time with chlorine for inactivation; oocysts can survive for days in the chlorine levels that are typically recommended for swimming pools (1–3 ppm free chlorine; 27 ).The continued reporting of cryptosporidiosis outbreaks associated with the use of treated recreational water venues underscores the importance of other prevention measures that reach beyond conventional pool chlorination and filtration, which are the primary barriers to infectious disease transmission (28 ).WBDOs of cryptosporidiosis have stimulated the use of alternative treatment technologies and other potential risk-reduction steps to keep swimming venues safe. Ultraviolet light (29–31 ) and ozonation (27,32) disinfection effectively inac­

### 18 **MMWR September 12, 2008** 

**FIGURE 8. Number of recreational water-associated outbreaks** **(n = 557),* by year and illness** **† — United States, 1978–2006** 

45

30

15

0 Other
ARI
Skin
AGI §

1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 Year * Single cases of primary amebic meningoencephalitis (n = 60) have been

removed from this figure; therefore, it is not comparable to figures in previous Surveillance Summaries. † AGI: acute gastrointestinal illness; Skin: illness, condition, or symptom

related to skin; ARI: acute respiratory illness; Other: includes keratitis, conjunctivitis, otitis, bronchitis, meningitis, meningoencephalitis, hepatitis, leptospirosis, and combined illnesses. § All outbreaks of legionellosis (i.e., Legionnaires’ disease and Pontiac fever)

are classified as ARI.



### tivate Cryptosporidium and are available for use at aquatic venues. Other potential risk-reduction steps include increased circulation flow rates, flocculants, remedial biocidal shocktreatments [i.e., routine hyperchlorination: 20 ppm free chlorine for 12.75 hours or the equivalent ( 31,33 )], and occupancy-dependent water replacement. In addition, cryptosporidiosis outbreaks highlight the need for improvedoperator training and continued education of the general public concerning healthy swimming practices to reduce the risk for RWI.

Because Cryptosporidium is resistant to the chlorine levels used in pools, outbreaks can occur, even in facilities that are well-maintained. Therefore, rapid public health response and increased community involvement are needed to prevent the expansion of these outbreaks (34). One cryptosporidiosis outbreak (Iowa, June 2005) that occurred in a community swimming pool demonstrates how a rapid community-wide public health response during the early stages of an outbreak canhelp control the potential spread of illness into the community. In Iowa, detection and investigation started 2 weeks after exposure. The response included mitigating actions (e.g., ordering hyperchlorination of the implicated pool and all pools within a 20-mile radius and then confirming compliance; containing the outbreak through collaborative efforts between epidemiologists and environmental health specialists; posting signs at the implicated pool’s entrance; instructing those with diarrhea not to enter the pool; and educating the public about good hygiene practices). The investigation indicated that no transmission had apparently occurred outside of the single implicated community pool, suggesting that these control measures might have prevented further spread. An interstate cryptosporidiosis outbreak (Kentucky, June 2005; and Ohio, August 2005) highlighted the need for additional intra-agency collaboration (e.g., between epidemiologists detecting casesand environmental health specialists permitting and inspecting pools) and communication between states.

Modification of swimming behavior is a critical component in reducing recreational water-associated outbreaks. Swimming is essentially communal bathing, and continued swimmingduring diarrheal illness and the common occurrence of swallowing recreational water pose a public health challenge. Multiple findings underscore the relation between humanbehavior and disease transmission at recreational water venues. First, in multiple outbreaks, fecal accidents were observedat the implicated pools on the days when the outbreak exposures were thought to have occurred (Florida, August 2006; and Illinois, July 2006). Second, at least five outbreaks (New York, June 2005; Ohio, August 2005; Illinois, July 2006; Minnesota, September 2006; and South Carolina, July 2006) were caused by Cryptosporidium hominis , indicating a human source of water contamination. Third, swallowing water at the implicated recreational water venue was associated with illness in three outbreaks (Colorado, August 2006; Florida, June 2005; and New York, June 2005). All of these outbreaks highlight how recreational water can amplify transmission of fecal-oral pathogens. These findings underscore the need forpublic education about the importance of not swimming during diarrheal illness and not swallowing recreational water,and the importance of clarifying with the public that recreational water is neither drinking water nor sterile. Aquatic facilities should be diligent about informing patrons of these public health concerns and emphasizing that persons with diarrhea should not swim and all swimmers should practicegood hygiene. These policies should apply to all patrons, particularly young children and visitors from high-risk settings(e.g., child care centers), which have diarrhea exclusion policies but might not enforce them routinely. They also should apply to all aquatics facility staff. Standardized policies for restricting staff who are ill with diarrhea from entering pools, similar to restricting ill foodhandlers from food preparation, should be established, implemented, and enforced (35 ). Finally, good hygiene is essential to ensure the cleanliness ofswimmers entering pools. An adequate number of functioning, accessible hygiene facilities (i.e., toilets, diaperchanging areas, and showers) should be located near poolsand should provide hot water and handwashing access to promote compliance. Documented fecal contamination of persons (36 ) suggests that swimmers should be encouraged to shower thoroughly (i.e., washing the peri-anal surface in par­

### 19 **Vol. 57 / SS-9 Surveillance Summaries** 



### ticular) before going to or entering the pool. Diaper-changing facilities, with handwashing stations, should be located close to or at the poolside to encourage hygienic diaper-changing and handwashing. Chemical Toxicity

During 2005–2006, pool chemicalsor disinfection by-products were confirmed as the etiologic agent in one (Ohio, July 2005) and suspected to be the etiologic agent in four (Minnesota, April 2005; Illinois, June 2006; Nebraska, December 2006; and NewYork, March 2006) pool-associated outbreaks. Chemicals are added to pool water to protect against microbial andalgal growth, improve the water quality, maximize the efficacy of the disinfection process (e.g., pH control), andprevent corrosion and scaling of equipment. However, these same chemicals can become sources of illness or injury **FIGURE 9 . Recreational water-associated outbreaks of gastroenteritis, by type of exposure and etiologic agent— United States, 1997–2006** 



### if they are not properly handled or if water quality and ventilation are poor. In an ARI outbreak in Ohio, a pool recirculation pump shut down for unknown reasons, but the chemical feed pump continued to feed hypochlorous acid and muriatic (hydrochloric) acid into the recirculation system, resulting in the release of chlorine gas into the pool that was still in use by swimmers when the recirculation pump was restarted. Nineteen persons became ill, of whom four of themwere hospitalized. A dermatitis outbreak (Illinois) was suspected to have resulted from water chemistry deficiencies (pH<7 and chlorine level at 0 ppm) that occurred when the automatic chemical-feeding system malfunctioned. These outbreaks underscore the need for engineering controls (e.g., an electrical interlock system that shuts down the chemical feedpump when the recirculation pump shuts down), regular systems checks, and preventive maintenance of equipment.

Three additional outbreaks of acute respiratory symptomsor eye irritation were suspected to have resulted from an accumulation of chloramines in the water and air of indoor pools. Chloramines are disinfection by-products that result fromchlorine oxidation of nitrogenous compounds (e.g., perspiration, saliva, urine, and body oils) commonly shed into pools by swimmers (20 ). Chloramines are produced in the waterand volatilize into the surrounding air. In indoor pool settings, chloramines can accumulate in the enclosed space if ventilation is inadequate (21 ). The resulting high levels of * These include outbreaks of Salmonella, Campylobacter, Plesiomonas , and mixed pathogens. Type of exposure (n = 167) Etiologic agent (n = 167)

Untreated

water 37.7% Norovirus 12.0% Treated water 62.3% Unidentified 15.0%

Etiologic agent: untreated water (n = 63) Etiologic agent: treated water (n = 104) Other* 4.2%
Giardia spp. 3.6%
Shigella spp. 9.0%

Escherichia coli 9.0% Cryptosporidium spp. 47.3%

E. coli 19.0%

Unidentified

25.4% Norovirus 20.6%

Shigella spp.

12.7%
Cryptosporidium spp. 12.7%

Giardia spp. 4.8% Other* 4.8% Cryptosporidium spp. 68.3% Unidentified %

spp. 2. %

8.7

E. coli Other* 3.8%
9
2.9% spp. 6.7%
Norovirus 6.7%

Giardia

Shigella



### chloramines can cause ocular, respiratory tract, and mucous membrane irritation (20 ); these high levels in indoor pool settings are also potentially linked to asthma (37). The investigation of the Nebraska outbreak, which resulted in one young swimmer being admitted to a pediatric intensive-care unit for severe chemical epiglottitis and laryngotrach-eobronchitis,revealed inadequate facility maintenance that resulted in prolonged deterioration of the water chemistry (e.g., 0.8 ppm free chlorine, 4.2 ppm combined chlorine, and a pH = 3.95) (38 ).The shortage of laboratories that perform analyses for airborne chloramines and the variability in indoor air quality from day-to-day impedes investigators’ ability to respond to reports of ocular and respiratory distress related to indoor pools or to obtain rapid and quantitative air measurements at implicated pools. Water-testing data useful for evaluating an indoor air-quality problem include the pH level and total (i.e., free plus combined chlorine) and free chlorine concentrations, which can be used to calculate the level of combined chlorine in the water. Levels that exceed test kit capacity should be re-measured by making dilutions using distilled water. These outbreaks underscore the need to train pool operators and aquatic staff so that they routinely monitor and maintain water chemistry to protect the health of patrons and staff.

Air-quality improvements in indoor pools will require technological improvements in water chemistry and treatment and air circulation and ventilation. New studies suggest that

### 20 **MMWR September 12, 2008** 



### installation of ultraviolet treatment devices in pool water recirculation systems can reduce pool chloramine levels (39 ) and also can effectively inactivate pathogens (including chlorine-resistant Cryptosporidium ) (39,40 ). Plans to improve air quality also can be aided by working with the public to improve swimmer hygiene. The resulting reduction in urine and other nitrogenous waste (e.g., decreased public urination in pools and increased showering before entering pools) should lead to reductions in chloramine levels in both water and air. Such an effort should raise public awareness about the role of urine and sweat in creating the irritants associated withindoor pool swimming. Operators should encourage showering before entering any pool or spa and facilitate frequentbathroom breaks for swimmers, particularly for young children (e.g., instituting adult-only swim times and short closures for water-quality testing).

Multiple challenges are associated with understanding thenumbers of water-related, chemical illnesses at aquatic venues. Lack of rapid testing and routine testing for chloramines suggests that surveillance for recreational water-associatedoutbreaks of acute chemical poisoning is likely to have multiple barriers, resulting in underestimation of the true magnitude of the problem. Acute chemical-related WBDOs might be more likely to involve first responders than the traditional epidemiologic or environmental health staff investigating otherWBDOs and reporting to WBDOSS. As a result, more efficient reporting will require building strong and effective intraand interagency communication networks within health departments and with other groups (e.g., first responders andpool operators) to improve the reporting of WBDOs associated with recreational water.


## Spas

Spas are susceptible to human contamination by the same pathogens that contaminate swimming and wading pools, butoutbreaks of gastrointestinal illness from spas might be limited because spa usage does not involve as much full body (e.g., head-to-toe submersion) activities as pools, resulting in less water ingestion. However, spa operation is challenging because of difficulty with maintaining disinfectant levels at higher water temperatures or with aeration and the relatively high bather load to water volume typical of spas. As a result, these venues are ideal for amplification of naturally occurring environmental contaminants (e.g., thermophilic pathogens, P. aeruginosa , and Legionella).
Skin Infections

Spa-associated outbreaks are commonly associated with dermatitis and folliculitis; P. aeruginosa is the most commonly reported agent implicated in these settings ( 41 ). During 2005– 2006, four WBDOs caused by Pseudomonas (Connecticut, April 2005; New Mexico, April 2005; Wisconsin, July 2005; and Kansas, December 2006), and five WBDOs suspected to have been caused by Pseudomonas (Minnesota, March 2005;Vermont, February 2005; Georgia, February 2006; Tennessee, March 2006; and Wisconsin, February 2006) were reported; four of these outbreaks involved spas, and five involved both spas and pools. The frequent co-location and useof both spas and pools by patrons means that it can be epidemiologically difficult to implicate a particular pool or spa at a single venue. However, amplification of Pseudomonas is most likely to occur at the higher temperatures in spas ( 42 ). Nearly all of the Pseudomonas-associated outbreaks occurredas a result of spa use at a hotel, motel, or rented cabin, underscoring the need for improved recreational water quality in these transient visitation, travel-associated settings. Multiple outbreaks included large gatherings (e.g., birthday pool party [Connecticut] and sports tournament [Minnesota]), which can rapidly overwhelm the disinfection capacity of spas and lead to bacterial amplification. In addition, these gatherings often occurred on weekends (Wisconsin), when hotel staff trained in spa maintenance are likely to be off duty. Hotels and motels should consider having only trained employeesoperate and maintain pools and spas, particularly on weekends when usage is typically highest. Enhanced water-quality monitoring and maintenance should be considered when a large group or event at a hotel is scheduled. Users should be educated about not adding contaminants that might disrupt the spa’s water chemistry (e.g., shampoo [Minnesota] and wine [Georgia]).

To prevent spa-associated outbreaks, operators must understand the risk factors and steps that can be taken to limit transmission of pathogens, particularly thermophiles. Proper chlorination or bromination effectively kills Pseudomonas and other skin-infecting bacteria. A review of 18 Pseudomonas outbreaks demonstrated that inadequate disinfection was associated with all outbreaks linked to spas ( 43 ). Bacterialamplification and biofilm build-up can be prevented by properly maintaining spas, ensuring that chlorine or bromine levels consistently remain >2 ppm, and that pH levels remain ina range of 7.2–7.8. Poor maintenance of spas has been welldocumented ( 44 ), and studies have demonstrated that Pseudomonas and other bacteria can remain protected in spa biofilms, even in the presence of adequate disinfectant, then rapidly proliferate if the disinfectant level drops ( 42 ). Legionellosis

Legionellae, which cause both LD and PF, are ubiquitous in freshwater environments ( 45 ). Environmental conditions in

### 21 **Vol. 57 / SS-9 Surveillance Summaries** 



### whirlpool spas (e.g., warm temperatures and water aerosolization) promote the amplification and transmission of the bacteria when combined with low or erratic disinfectant levels. Exposure to Legionella is more likely to occur in the absenceof adequate levels of disinfectant, underscoring the importance of maintaining adequate disinfectant levels and pH control. When lapses in preventive measures result in a legionellosis outbreak, morbidity can be reduced by rapid recognition ofthe outbreak, identification of its source, and immediate implementation of remediation. Remediation methods include cleaning and disinfecting the spa to eliminate Legionellacolonization and performing follow-up cultures for Legionella to ensure that re-colonization does not occur ( 46 ). All eight legionellosis WBDOs associated with recreational water during 2005–2006 were associated with spas. Five of these outbreaks occurred at hotels which highlights the role of travel in Legionellatransmission and illustrates the potential difficulty of detecting travel-associated illnesses when travelers disperse to their resident state or country. CDC’s supplementary reporting system for legionellosis collects exposure and travel information. In a 2005 CSTE position statement ( http://www.cste.org/PS/2005pdf/final2005/05­ID-01final.pdf), surveillance and active follow up of potential travel-associated case reports was recommended position statement to improve detection of travel-associated clusters of illness and to increase opportunities for disease prevention. During 2005–2006, a total of 10 clusters were identified ( 47 )although not all met WBDO definition. After CSTE’s recommendations in 2005, CDC 1) improved communicationwith international, state, and local public health partners concerning travel-associated LD cases; 2) developed a standardized notification and tracking system; and 3) created a dedicated e-mail address for case reporting (travellegionella@cdc.gov). In addition, CDC’s legionellosis website (http://www.cdc.gov/legionella) has been updated to provide useful tools for investigating legionellosis outbreaks (including sample questionnaires),sample letters for hotel management, and protocols for environmental assessments of water systems.



## Interactive Fountains/Wet Decks and Fill-and-Drain Pools

Infectious Gastroenteritis

Certain treated water venues (e.g., interactive fountains,which also are called wet decks or spray parks) might be overlooked as potential sites for transmission of infection or poolregulation because they do not have standing water as traditionally found in swimming pools. These venues are particularly prone to contamination by fecal material, vomit, and dirt because of the young users of the small volume of recirculating water. These contaminants can potentially drain into the water reservoir and be sprayed back on users, increasing the likelihood of contaminated water ingestion. The use ofinteractive fountains has previously been associated with outbreaks of gastroenteritis ( 48), and outbreaks reported here (Louisiana, August 2005; New York, June 2005; California,July, 2006; and Florida, May 2006) demonstrate that transmission continues to occur in these settings. Not all states regulate interactive fountains which might increase chance of improper design, maintenance, or operation in these venues.

In one of the largest outbreaks reported to the WBDOSS,approximately 2,300 persons developed cryptosporidiosis following exposure to a New York spray park. The environmental investigation revealed that recycled water was not adequatelyfiltered and disinfected. In response, New York passed emergency legislation requiring that supplementary disinfection (e.g.,ultraviolet radiation or ozonation) be installed on water returning through the sprayers. Designs that improve water treatment for these interactive fountains are needed to reduce the risk for RWIs. Reports of investigations from three additional cryptosporidiosis outbreaks (California, 2006; Florida, 2006; and New York 2005) indicated inadequate disinfection levels (<1.0 ppm chlorine) and the use of sand or cartridge filters, both of which might not be adequate for Cryptosporidium oocyst removal. Filters with diatomaceous earth might be more effective at removing oocysts than sand or cartridge filters.

The use of tap water to fill or operate temporary aquaticvenues (e.g., fill-and-drain pools) used by young children continues to be a public health challenge (California, July 2006;and Wyoming, July 2005). Lack of disinfection and the traditional use by toddlers and diaper-aged children have resultedin multiple outbreaks being associated with use in both residential and institutional settings ( 12,49,50). In the California outbreak, nine persons became ill with AGI after attending a pool party where guests swam in a plastic pool filled with untreated tap water. Three children were hospitalized; S. sonneiwas confirmed in stool samples from six ill persons. In Wyoming, an outbreak of campylobacteriosis occurred after two families filled a pool with untreated water from a shallow well. In addition, a dog known to roll around in cow feces entered the pool. The potential risk for infection associated with using temporary pools filled with tap water without additional disinfection and filtration should be considered before they are used in residential settings. To reduce the risk for pathogen transmission, persons with gastroenteritis should be excluded, and the pool should be drained and cleaned daily. On the basis of documented outbreaks, fill-and-drain pools should be eliminated from institutional settings or large group events (50 ).

### 22 **MMWR September 12, 2008** 



## Lakes and Rivers

Infectious Gastroenteritis

Although the proportion of AGI outbreaks associated withuntreated venues (e.g., lakes and rivers) relative to treated venues decreased over the previous decade, the number of outbreaks associated with untreated venues has remained relativelyconstant (Figure 10). During 2005–2006, a total of 13 outbreaks of gastroenteritis associated with untreated freshwater venues were reported; all of these were linked to swimming in lakes or ponds. Freshwater venues have a higher proportionof outbreaks caused by bacterial and viral etiologic agents compared with treated water venues (Figure 5).

Multiple studies have determined the utility of water-quality monitoring ( 16 ) for assessing the associated risk for swimmer illness ( 18) in large bodies of water (e.g., Great Lakes and the ocean). However, the small inland water bodies associated with the outbreaks in this report do not have consistent external sources of contamination (e.g., sewer overflow), suggestingthat swimmers might be an important source of water contamination and infection transmission. As with treated venues, human behavior plays a key role in the spread of pathogens in untreated bodies of water. Modification of swimmerbehavior might be a more critical factor in natural water venues that lack the benefit of disinfection and filtration barriers to transmission. Recommendations for swimmer hygiene in natural waters are the same as those previously discussed for treated pools. In addition, beach managers and swimmers should be aware that shallow, poorly circulated swimming areas, although desirable to many swimmers, might pose a higher risk of exposure to certain pathogens compared to deeper, well circulated swimming areas. Potential methods to improve circulation of water through beach areas should be explored to reduce the longevity of focal, swimmer-derivedcontamination and waterborne-disease transmission. Reducing exposure to high fecal indicator bacterial levels at sites affected by runoff can be achieved by avoiding swimming immediately after heavy rainfall (reducing exposure to any increase in contaminated runoff) and by not swimming near storm drains or pipes that might release contamination into water bodies (24 ). Primary Amebic Meningoencephalitis

During 2005–2006, five fatal cases of PAM caused by N. fowleriwere reported; for two of these cases, there was possibly a common exposure to either a creek or a small spray park. For the remaining three cases, no common exposure was identified (Tables 4, 10). This rare disease is of public health importance because of the high fatality rate associated with infection (>99%) ( 51 ) and the public alarm it raises for **FIGURE 10. Number of recreational water-associated outbreaks of gastroenteritis (n = 259), by water type and year — United**  **States, 1978–2006**

5 10 15 20 25

Treated
Untreated

1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 0

Year


### use of natural waters in the southern tier states in the United States. N. fowleri is a free-living ameba that proliferates in warm freshwater and hot springs. Disease occurs when the ameba coincidentally enters the nasal passages, travels to the olfactory lobe of the brain, and infects brain tissue. The five cases all occurred in southern tier states (Arizona, Georgia, Oklahoma, and Texas) during warm weather months (Tables 4, 10). Three of the five children who died of PAM during 2005–2006 had participated in activities in warm water before onset of symptoms, similar to other known cases of PAM. The source of exposure for the two Oklahoma cases could not be determined despite a public health investigation.

The low number of Naegleria infections makes it difficult to determine why certain persons become infected compared with the millions of others with the same or similar exposures to waters across the United States. As a result, the efficacy of existing risk-reduction strategies are uncertain. The finding of Naegleria in the majority of lake water surveys conducted in southern tier states suggests that this minimal likelihood of Naegleriainfection always will be associated with swimming in warm, freshwater lakes, rivers, and hot springs. While themost certain way to prevent infections is to refrain from swimming in these freshwater bodies, swimmers might reduce their risk for PAM by not swimming or jumping into bodies of warm freshwater, hot springs, and thermally polluted water (e.g., water around power plants); not swimming or jumping into freshwater during periods of high water temperature and low water volume; holding the nose shut or using nose clips when jumping or diving into bodies of warm freshwater; andrefraining from digging in or stirring up sediment while swimming in shallow, warm, freshwater areas. CDC is collaborating with CSTE to more effectively describe the scope of Naegleria infections in the United States, improve surveillance, and analyze available exposure and environmental occurrence data to develop more evidence-based risk-reduction measures and messages ( 52 ).

### 23 **Vol. 57 / SS-9 Surveillance Summaries** 



### Leptospirosis

Although infections caused by Leptospiraare considered to be more common in tropical and semitropical areas of the world ( 53 ), outbreaks reported during 2005–2006 illustrate the potential risk for leptospirosis outbreaks associated with recreational water contact in the United States. Leptospiracanbe found in the urine of infected wild and domesticated animals, so contamination of natural waters can occur where infected animals live. The route of transmission in humans usually is through contaminated water contact with broken or abraded skin or through contact with the mucosal surfaces of the eye, mouth, nasopharynx, or esophagus. Exposure might also occur through inhalation, ingestion, or prolonged immersion in water, resulting in increased permeability of theskin. Increased skin permeability might play a role in infections resulting from contact with contaminated surface water after flooding ( 54 ) or with prolonged use of contaminated surface waters as part of sports or other events (e.g., triathlons) ( 55,56 ). Two outbreaks of leptospirosis involving 46 personswere reported for 2005–2006 as well as a previously unreported outbreak in Hawaii in 2004 ( 57 ). One outbreak in California (July 2005) was associated with persons working in a drought-affected stream. The second larger outbreak occurred in Florida (November 2005) and was associated withparticipation in an adventure race. This is consistent with previous outbreaks in other similar competitive venues ( 55,56 ). To reduce risk for infection, persons should wear protective clothing, avoid swimming when they have open wounds or abrasions and avoid water contaminated by animal urine.
Cercarial Dermatitis

During the 2005–2006 surveillance period, two WBDOs of suspected cercarial dermatitis caused by avian schistosomes were reported (California, July 2005 Ohio August 2006). Although the diagnosis was not confirmed, this self-limited disease is known to occur among persons exposed to lakes across the United States where infected birds contaminate water supporting the intermediate host snail ( 58). The risk for acquiring cercarial dermatitis might be reduced by warning swimmers of potentially contaminated lakes, avoidingshallow swimming areas where infected snails reside, instituting a snail control program, and by not attracting birds to swimming areas (e.g., by not feeding them).



## Marine Water

No waterborne disease outbreaks associated with marinewaters were reported to WBDOSS before 2005–2006; however, evidence from multiple sources demonstrates that contamination of marine waters is common and that swimmers in marine waters are at increased risk for acquiring AGI (23,59 ). States and territories report water-quality testing results and notification data for their coastal and Great Lakes recreational water to EPA. In 2006, 32% of monitored beaches were affected at least once by either an advisory or closing as a result of the EPA microbial fecal indicator limits being exceeded or water-quality standards not being met ( 17). Multiple studies have linked these water-quality indicators with increased risk for RWIs (23,59,60 ), although RWIs also canoccur when water-quality indicators are within established limits (24 ). The reasons for a lack of reported marine-associated outbreaks might include the wide geographic spread ofbeachgoers, the fact that some of the marine-associated illnesses are not enteric illnesses typically linked to waterborne causes, and a lack of illness attribution to marine waters.
Vibrio Illness

Although WBDOs associated with marine waters might be difficult to detect, single cases of Vibrio infections from marine water exposure might be more likely to be reported because of the severity of the illness associated with infection. The number of Vibrioinfections associated with water exposures during 2005–2006 (n = 189) was higher than the number reported in 2003–2004 (n = 142), although recreational water exposure constitutes only a small fraction (14.7%) of the 1,287 vibriosis cases from all exposures reported in 2005– 2006 ( 61 ). Some of the increase in reported cases for 2005 might be attributable to flood water exposure in the Gulf Coast immediately following Hurricane Katrina ( 62) when active case-finding facilitated identification of Vibrioinfections. Reported hurricane-related infections were primarily among persons with wounds who waded through flood waters. The majority of hurricane-related Vibrioinfections were caused by V. vulnificus , which predominately occurs in the Gulf Coast. Wound infections from V. vulnificus can cause severe illnessand sequelae, including septicemia and the need for amputation. For nonfoodborne cases of V. vulnificus infection, thehospitalization rate is approximately 90% and the case fatality rate is 17%–24% ( 63,64), similar to the 22.3% case fatality rate among cases reported during 2005–2006 (Table 8).Disease is more common and severe among persons with preexisting wounds and other medical conditions (e.g., diabetes, heart disease, or liver disease) ( 64,65 ). V. parahaemolyticus and nontoxigenic V. cholerae infections were also reported among persons with hurricane-related Vibrioinfections. The burden of wound-related vibriosis is unknown, although an estimated 8,000 Vibrioinfections occur annually, including an estimated 2,800 annual cases not associated with food exposure ( 64 ).CSTE added vibriosis to the list of nationally notifiable diseases in January 2007. Vibriosis is reportable in 35 states,

### 24 **MMWR September 12, 2008** 



### although all other states and territories can report vibriosiscases to CDC. Cases are reported to CDC by using the Cholera and Other VibrioIllness Surveillance report form, which is available athttp://www.cdc.gov/nationalsurveillance/PDFs/ CDC5279_COVISvibriosis.pdf. Annual summaries of national data on vibriosis are available at http://www.cdc.gov/ nationalsurveillance/cholera_vibrio_surveillance.html

. Improved surveillance and reporting are designed to increase understanding of the magnitude and distribution of Vibrio illness related to marine water, to better characterize the risk and contributing environmental factors, and to guide thedevelopment of appropriate prevention messages (e.g., persons with wound or certain preexisting conditions not swim in warm marine water). Seabather’s Eruption

One outbreak was reported for 2005–2006 in which swimmers were exposed to marine water. Certain ill persons hadsymptoms consistent with Seabather’s Eruption, a skin condition caused by contact with toxins from stinging jellyfish larvae. However, the majority of persons also exhibited an influenza-like illness which, although previously associated with Seabather’s Eruption ( 66 ), could also indicate anotherwater-associated etiology. Seabather’s Eruption occurs primarily in the marine waters off Florida, the Gulf of Mexico, and the Caribbean Sea particularly during spring and summer months. Whereas risk factors associated with developing Seabather’s Eruption are not fully understood, swimmers might be able to reduce their risk by removing bathing suits and thoroughly showering to remove jellyfish larvae after marine water exposure ( 67). Ongoing research is needed to understand the water conditions that lead to increased risk for illness among swimmers so that appropriate risk-reduction messages can be given to ocean beach visitors.


## Previously Unreported Outbreaks

The retrospective review of waterborne-disease outbreaks in Minnesota, New York, and Tennessee by EHS-Net Waterstaff resulted in the reporting of 30 previously unreported recreational water–associated outbreaks and case reports (Table 11). The addition of previously unreported outbreaks increases understanding about the epidemiology of waterborne disease in these jurisdictions. The success of the EHS-Net Water surveillance improvement effort underscores the utility of acquiring personnel who can focus on waterborne disease detection, investigation, and reporting ( 13 ). An additional outbreak from 2004 was reported by Hawaii ( 57 ). 

## Aquatic Facility-Related Health Events not Associated with Recreational Water Use

All 32 aquatic facility–related health events not associated with recreational water use (Table 12) were reported by New York, which had captured these events through a system, which mandates reporting of chemical injuries. Three events, all of which involved mixing of incompatible pool chem icals that resulted in the release of chlorine gas, were reported during 2005–2006. The first outbreak of ARI resulted from a spill of 50–75 gallons of hypochlorous acid (i.e., bleach), which mighthave interacted with other chemicals in the spill area. The second event resulted from using a container that was previously used for hypochlorous acid as a container for the acid used to adjust pool pH. Subsequent contact of the pool acid with the hypochlorous acid residue released a chlorine gas plume. Thethird event involved adding both calcium hypochlorite (chlorine) and trichloro-s-triazinetrione (a chlorinated isocyanurate commonly called trichlor) to the pool chlorinator system, which resulted in a release of chlorine gas. The material safety data sheet for trichloro-s-triazinetrione states that it is not to be mixed with other chemicals, especially calcium hypochlorite;alkalis; and other swimming pool/spa chemicals in their concentrated forms. These events and others (Table 12) highlight the need for new or improved 1) pump room and chemicalstorage area design and construction (e.g., improved ventilation, and chemical containment and separation), 2) chemicalpackaging (e.g., to easily differentiate between key pool chemicals), 3) chemical storage (e.g., to prevent mixing accidents), 4) staff training on how to safely store and handle chemicals and maintain and repair chemical-using pool systems, and 5) emergency response protocols.



## Prevention

Prevention of RWIs is likely to be accomplished only througha concerted team effort by public health professionals, swimming venue operators, and the general public. Operators at treated water venues are equipped with various methods that should be employed to prevent outbreaks. The traditional reliance on two water-treatment barriers at treated water venues, chlorination and filtration, likely needs to be expanded to include in-line (i.e., usually installed after filtration and beforechlorination) supplemental disinfection (e.g., ultraviolet treatment and ozonation) to increase the level of protection against pathogens, particularly chlorine-resistant Cryptosporidium . Suchsupplemental disinfection systems will not eliminate waterbornedisease transmission (because these systems are circulationtime dependent), so improved monitoring of water-quality and

### 25 **Vol. 57 / SS-9 Surveillance Summaries** 



### facility-maintenance programs and improved policies to educate the public and decrease contamination of aquatic facilities with bodily waste also are critical. In response to the lack of protective barriers at untreated swimming venues (e.g., lakes and oceans), beach managers and public health officials shouldimplement water-quality testing programs and educate swimmers concerning appropriate prevention measures (e.g., not swimming after heavy rainfall). Specific efforts should address environmental pathogens unlikely to be prevented by current water-quality guidelines (e.g., illnesses caused by Vibrio and otitis media infections).

Public health professionals should 1) improve training for pool inspectors, 2) update and improve pool codes to stay current with changing designs and needs demonstrated by outbreaks summarized in this report, 3) lead and collaborate with aquatic staff to educate the general public, and 4) develop expertise in detecting and investigating recreational water-associated outbreaks, particularly those associated with chemicals. Safe handling and use of chemicals at aquaticfacilities needs to be a standard training element that is regularly reinforced. In addition, to improve overall indoor air quality, public health professionals and pool managers need to understand the importance of implementing improvements in pool water quality, swimmer hygiene, air-turnover rates, and ventilation.

Educating swimmers can play a vital role in reducing RWIs by encouraging them to follow basic guidelines for healthy swimming. Fecal shedding of pathogens is common (36 ), so reducing the risk for water-related infection is best achievedby implementing diarrhea-exclusion policies, using appropriate hygiene measures, and advising the public to avoid swallowing recreational water. In addition, the public can inform themselves about RWI prevention. They canbecome activist swimmers (e.g., checking chlorine and pH levels themselves) and advocate for healthy swimming venues.



# Conclusion Data collected by WBDOSS are used to characterize the epidemiology of waterborne disease and outbreaks associated with both recreational and drinking water. Swimming is a common activity in the United States ( 68). Certain diseasecausing agents are transmitted through shared bodies of water, and new waterborne pathogens that infect humans (e.g., Cryptosporidiumand toxigenic E. coli ) have emerged in the previous 3 decades. RWIs and outbreaks are associated with both treated and untreated water and with every type of aquatic venue. Common themes derived from the outbreaks in this report include 1) low disinfectant levels or poor filtration; 2) inadequate water-quality monitoring; 3) high bather loads during large events; 4) breakdowns of equipment and delayed detection or repair times; 5) not using ultraviolet radiation or ozonation to treat for Cryptosporidiumin pools and interactive fountains; 6 ) accumulation of combined chlorines in poolsaccompanied by inadequate indoor air ventilation; 7) inadequately trained aquatic staff, particularly on safe chemical handling practices, 8) lack of communication within and between public health agencies; 9) outbreaks occurring on weekends when trained staff might be off duty; 10) lack ofawareness by the general public of appropriate healthy swimming behaviors; and 11) lack of health department familiarity with chemical-associated RWIs.

Although no easy solution exists for reducing WBDOs associated with recreational water, a sustained effort by theswimming public, the aquatic management sector, and public health agencies can reduce the associated risk. The millions of persons in the United States who use recreational water every year can best reduce their risk by staying informedregarding the health and safety concerns associated with swimming. Public health officials should lead this educational effort to promote healthy swimming behaviors. Prevention methods discussed in this report should help make swimming experiences healthier, safer and more enjoyable. The aquatic sector also can benefit from the recommendations, which address changes that are needed in operation, maintenance,and chemical handling procedures. Large numbers of violations of state and local pool codes occur each year ( 15,44 ),indicating that improved pool operation, disinfection policies, and enforcement are needed to prevent RWIs (33 ). In addition, improvements in indoor air quality monitoring and widespread dissemination of validated testing protocols are needed to support improved air quality in indoor swimming pool settings. As a result of recommendations from a 2005national workshop on how to prevent RWIs, CDC is sponsoring development of a national model aquatic health code (MAHC), which involves public health and aquatics sectorpersonnel from across the country and is designed to transform the typical health department program into a data-driven, knowledge-based, risk-reduction effort to prevent disease and injuries and promote healthy recreational water experiences.MAHC will provide uniform guidelines for the design, construction, operation, and maintenance of swimming pools and other disinfected swimming venues. Although nonregulatory in nature, the MAHC should ensure that the best availablestandards and practices for protecting public health are available for adoption by state and local agencies. Further information is available at http://www.cdc.gov/healthyswimming/ model_code.htm.

### 26 **MMWR September 12, 2008** 



### Public health professionals at all levels of government should lead a multidisciplinary approach to prevent RWI thatincludes surveillance, health education, epidemiologic studies, laboratory support, and environmental health research.Educational resources and campaigns are needed for swimmers, parents, aquatic venue operators, and public health staff. Improved communications, particularly during outbreak investigations, between all areas of the public health system(e.g., infectious disease, environmental health, and surveillance staff) and between agencies in neighboring jurisdictions can 1) enhance awareness concerning ongoing occurrences ofRWIs, 2) facilitate reporting to WBDOSS in a timelier manner, and 3) strengthen WBDO investigations and responsesto protect the public. The timely collection of clinical specimens and water samples for testing during a WBDO investigation and prompt initiation of an environmental investigation will result in more rapid identification of the etiologic agent and determination of the conditions leading to the outbreak.However, the capacity of public health departments and laboratories to detect and investigate potential WBDOs varies and needs to be strengthened to meet these challenges. WBDO investigations typically require input from various disciplines, including infectious disease epidemiology, environmental health, clinical medicine, water and sanitation engineering,chemists/toxicologists, and microbiology. Additional crosstraining of existing personnel in these areas or additional staffing and resources are needed to improve WBDO detection, investigation, and reporting. Other methods of improvingsurveillance at the local, state, and federal levels include additional review and follow-up of information gathered through other mechanisms (e.g., media reports or emergency responder reports of illness associated with recreational water venues).CSTE passed a 2006 position statement making waterbornedisease outbreaks, as a unit of reporting, nationally notifiable and reportable to CDC starting in 2007. Adoption of thisCSTE recommendation at the state level through statespecific legislative action might improve reporting of waterborne outbreaks. In addition, to improve timeliness and completeness of reporting, CDC and EPA are collaborating with public health jurisdictions to implement electronicreporting of WBDOs through the National Outbreak Reporting System (NORS). NORS will be a more systematic data collection tool that will provide public health agencies and waterborne-disease researchers with the evidence base they needto identify the causes of WBDOs and understand the interrelated factors contributing to these outbreaks.

EHS-Net Water, a collaborative project between EPA, CDC, and five state health departments, is an effort to improve WBDO identification, investigation, response, and reporting. Environmental health specialists initially focused on understanding their state-specific surveillance systems, leading to the reporting of numerous historical outbreaks to WBDOSS. Although this project has focused primarily on improving drinking water-associated disease outbreak surveillance, it also has markedly improved our understanding of recreational water-associated outbreaks in EHS-Net Water states, which demonstrates the value of investing water-specific resources in certain jurisdictions.

Focusing on improving awareness, training, resources, and communication will improve the quality of the data in WBDOSS. These efforts should make public health activities related to waterborne disease more efficient and, in turn, reduce the burden of recreational water-associated disease and injury (Box).

Acknowledgments



### The authors thank the following persons for their contributions to this report: state, local, and territorial waterborne-disease surveillance coordinators; state, local, and territorial epidemiologists and environmental health personnel; Mark Eberhard, PhD, Monica Parise, MD, Bonnie Mull, MPH, Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases, CDC; Lorraine Backer, PhD, Division of Environmental Hazards and Health Effects, National Center for Environmental Health, CDC; Charles Otto, Vince Radke, MPH, Division of Emergency and Environmental Health Services, National Center for Environmental Health, CDC; Sean Shadomy, DVM, MPH, Division of Foodborne, Bacterial and Mycotic Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases, CDC.

References

1. Craun GF, ed. Waterborne diseases in the United States. Boca Raton,

FL: CRC Press, Inc.; 1986.2. Liang JL, Dziuban EJ, Craun GF, et al. Surveillance for waterborne disease and outbreaks associated with drinking water and water not intended for drinking—United States, 2003–2004. In: Surveillance Summaries, December 22, 2006. MMWR 2006;55(No. SS-12):31–65.3. Blackburn BG, Craun GF, Yoder JS, et al. Surveillance for waterbornedisease outbreaks associated with drinking water—United States, 2001– 2002. In: Surveillance Summaries, October 22, 2004. MMWR 2004; 53(No. SS-8):23–45. 4. Lee SH, Levy DA, Craun GF, Beach MJ, Calderon RL. Surveillance

for waterborne disease outbreaks—United States, 1999–2000. In: CDC Surveillance Summaries, November 22, 2002. MMWR 2002;51 (No. SS-8):1–47.5. Barwick RS, Levy DA, Craun GF, Beach MJ, Calderon RL. Surveillance for waterborne disease outbreaks—United States, 1997–1998. In: CDC Surveillance Summaries, May 26, 2000. MMWR 2000;49(No. SS-4):1–35.6. Levy DA, Bens MS, Craun GF, Calderon RL, Herwaldt BL. Surveillance for waterborne-disease outbreaks—United States, 1995–1996. In: CDC Surveillance Summaries, December 11, 1998. MMWR 1998;47(No. SS-5):1–34.

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**BOX. Organizations that provide assistance in investigations of waterborne diseases and outbreaks (WBDOs) associated with recreational water exposure**  

### State health departments can request epidemiologic as- • Requests for Testing for Parasites sistance and laboratory testing from CDC to investigate Division of Parasitic Diseases WBDOs. CDC and the U.S. Environmental Protection National Center for Zoonotic, Vector-Borne and Agency (EPA) can be consulted regarding engineering and Enteric Diseases environmental aspects of recreational water treatment and Coordinating Center for Infectious Diseases, CDC collection of proper water samples to identify pathogenic Telephone: 770-488-7775 viruses, bacteria, and parasites, which require special pro- • Requests for Information on Testing for Legionella tocols for their recovery. Division of Bacterial Diseases National Center for Immunization and Respiratory • How to Report Waterborne-Disease Outbreaks Diseases

Waterborne Disease Outbreak Coordinator Coordinating Center for Infectious Diseases, CDC Division of Parasitic Diseases, MS F-22 Telephone: 404-639-2215 National Center for Zoonotic, Vector-Borne and Internet: http://www.cdc.gov/legionella

Enteric Diseases Coordinating Center for Infectious Diseases, CDC CDC provides public health professionals, clinicians, Atlanta, GA 30333 laboratorians, and persons in other allied health fields with Telephone: 770-488-7775 background and clinical information, guidance on invesFax: 770-488-7761 tigations, and resources concerning Legionnaires’ disease CDC Reporting Form (CDC 52.12, rev.01/2003) and Pontiac fever cases or potential outbreaks. Resources Internet: http://www.cdc.gov/healthyswimming/ include outbreak investigative tools, environmental samdownloads/cdc_5212_waterborne.pdf pling protocols, fact sheets, clinical evaluation and management guides, and laboratory testing protocols. • Requests for Testing for Viral Organisms

Division of Viral Diseases • Information Regarding Healthy Swimming National Center for Immunization and Respiratory CDC Internet: http://www.cdc.gov/healthyswimming

Diseases — Recreational water health communication and Coordinating Center for Infectious Diseases, CDC education resources for the general public and Telephone: 404-639-3607 aquatic staff — Pool and spa operation guidelines, including • Requests for Testing for Bacterial Enteric disinfection and responses to fecal accidents

Organisms — Outbreak investigation toolkit and technical Division of Foodborne, Bacterial, and Mycotic Diseases information concerning laboratory diagnostics. National Center for Zoonotic, Vector-Borne and • Information Regarding Beaches

Enteric Diseases EPA Internet: http://www.epa.gov/OST/beaches Coordinating Center for Infectious Diseases, CDC Telephone: 404-639-1798

7. Kramer MH, Herwaldt BL, Craun GF, Calderon RL, Juranek DD.

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### 28 **MMWR September 12, 2008** 

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Pulmonary epithelialintegrity in children: relationship to ambient ozone exposure and swimming pool attendance. Environ Health Perspect 2004;112:1768–71. 38. CDC. Ocular and respiratory illness associated with an indoor swimming pool—Nebraska, 2006. MMWR 2007;56:929–32. 39. Cassan D, Mercier B, Castex F, Rambaud A. Effects of mediumpressure UV lamps radiation on water quality in a chlorinated indoor swimming pool. Chemosphere 2006;62:1507–13. 40. Clancy JL, Marshall MM, Hargy TH, Korich DG. Susceptibility of five strains of Cryptosporidium parvum oocysts to UV light. J Am Water Works Assoc 2004;96:84–93. 41. Berger RS, Seifert MR. Whirlpool folliculitis: a review of its cause, treatment, and prevention. Cutis 1990;45:97–8. 42. Price D, Ahearn DG. Incidence and persistence ofPseudomonas aeruginosain whirlpools. J Clin Microbiol 1988;26:1650–4. 43. Gustafson TL, Band JD, Hutcheson RH Jr, Schaffner W. Pseudomonas folliculitis : an outbreak and review. Rev Infect Dis 1983;5:1–8. 44. CDC. Surveillance data from public spa inspections—United States, May–September 2002. MMWR 2004;53:553–5. 45. Fields BS, Benson RF, Besser RE. Legionella and Legionnaires’ disease: 25 years of investigation. Clin Microbiol Rev 2002;15:506–26. 46. CDC. Final recommendations to minimize transmission of Legionnaires’ disease from whirlpool spas on cruise ships. Atlanta, GA: US Department of Health and Human Services, CDC; 1997. 47. CDC. Surveillance for travel-associated Legionnaires’ disease—United States, 2005–2006. MMWR 2007;56:1261–3 48. CDC. Outbreak of gastroenteritis associated with an interactive water fountain at a beachside park—Florida, 1999. MMWR 2000;49: 565–8. 49. Dziuban EJ, Liang JL, Craun GF, et al. Surveillance for waterborne disease and outbreaks associated with recreational water—United States, 2003–2004. In: Surveillance Summaries, December 22, 2006. MMWR 2006;55:1–30. 50. CDC. Shigellosis outbreak associated with an unchlorinated fill-anddrain wading pool—Iowa, 2001. MMWR 2001;50:797–800. 51. Visvesvara GS, Stehr-Green JK. Epidemiology of free-living ameba infections. J Protozool 1990;37:25S–33S. 52. CDC. Primary amebic meningoencephalitis—Arizona, Florida, and Texas, 2007. MMWR. 2008;57:573–7. 53. Bharti AR, Nally JE, Ricaldi JN, et al. Leptospirosis: a zoonotic disease of global importance. Lancet Infect Dis 2003;3:757–71. 54. Levett PN. Leptospirosis. Clin Microbiol Rev 2001;14:296–326. 55. CDC. Update: leptospirosis and unexplained febrile illness among athletes participating in triathlons—Illinois and Wisconsin, 1998. MMWR 1998;47:673–6. 56. CDC. Update: outbreak of acute febrile illness among athletes participating in Eco-Challenge-Sabah—Borneo, Malaysia, 2000. MMWR 2001;50:21–4. 57. Gaynor K, Katz AR, Park SY, Nakata M, Clark TA, Effler PV. Leptospirosis on Oahu: an outbreak associated with flooding of a university campus. Am J Trop Med Hyg 2007;76:882–5.

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58. Verbrugge LM, Rainey JJ, Reimink RL, Blankespoor HD. Swimmer’s itch: incidence and risk factors. Am J Public Health 2004;94:738–41. 59. Wade TJ, N Pai, Eisenberg JN, Colford JM. Do U.S. EnvironmentalProtection Agency water quality guidelines for recreational waters prevent gastrointestinal illness? A systematic review and meta-analysis. Environ Health Perspect 2003;111:1102–9. 60. Nobles RE, Brown P, Rose J, Lipp E. The investigation and analysis of swimming-associated illness using the fecal indicator enterococcus in southern Florida’s marine water. Florida J Environ Health 2000;169: 13–19. 61. CDC. Cholera and other Vibriosurveillance system. March 21, 2008. Available at http://www.cdc.gov/nationalsurveillance/cholera_vibrio_ surveillance.html. 62. DC. Vibrioillnesses after Hurricane Katrina—multiple states, August– September. MMWR 2005;54:928–31. 63. Klontz KC, Lieb S, Schreiber M, Janowski HT, Baldy LM, Gunn RA. Syndromes of Vibrio vulnificusinfections. Clinical and epidemiologic features in Florida cases, 1981–1987. Ann Intern Med. 1988;109:318–23. 64. Dechet AM, Yu PA, Koram N, Painter J. Nonfoodborne Vibrio infections: an important cause of morbidity and mortality in the United States, 1997–2006. Clin Infect Dis 2008;46:970–6. 65. Oliver JD. Wound infections caused by Vibrio vulnificus and other marine bacteria. Epidemiol Infect 2005;133:383–91. 66. Wong DE, Meinking TL, Rosen LB, Taplin D, Hogan DJ, Burnett JW. Seabather’s eruption: clinical, histologic, and immunologic features. J Am Acad Dermatol 1994;30:399–406. 67. Kumar S, Hlady WG, Malecki JM. Risk factors for seabather’s eruption: a prospective cohort study. Public Health Rep 1997;112:59–62. 68. US Bureau of the Census. Statistical abstract of the United States: 1995. 115th ed. Washington, DC: US Bureau of the Census; 1995.

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# Appendix A Glossary of Definitions

aquatic facility-related health Chemical injury cases and outbreaks (e.g., mixing of pool chemicals that release toxic gas) events not associated with at aquatic facilities in which exposure to water was not the cause of illness. Although these recreational water events are not classified or analyzed as waterborne-disease outbreaks, they highlightimportant public health and safety concerns related to the design, operation, and maintenance of recreational water venues.

backwash Flow of water through filter element(s) or media in a reverse direction to dislodge accumulated dirt, debris, and/or filter aid, and remove them from the filter tank. backwash cycle Time required to thoroughly backwash the filter system.

bather load The number of bathers using a swimming pool or spa at any one time. The maximum bather load is usually determined by a state or local pool code, based on surface area and depth of the pool or spa.

biofilm Microbial cells that adhere to a surface through a matrix of primarily polysaccharide materials in which they are encapsulated. These can grow on piping and surfaces of aquatic venues and can be notoriously difficult to remove. They offer protection to microbes from disinfectants (e.g., chlorine) in the water.

cercarial dermatitis Dermatitis caused by contact with or direct invasion through the skin or a break in the skin by the cercariae (larval stage) of certain species of schistosomes, a type of parasite, for which the normal hosts are birds and nonhuman mammals. Dermatitis is an allergic response to contact with cercariae and does not lead to parasitic infestation in humans and produces no long-term disease.

class Waterborne disease and outbreaks are classified according to the strength of the epidemiologic and laboratory data implicating recreational water as the source of the disease or outbreak (see Table 1).

chloramines A group of disinfection by-pr oducts or weak disinfectants formed when free chlorine combines with nitrogen-containing compounds in the water (e.g., urine or perspiration). Tri- and di-chloramine can cause eye, skin, lung, and throat irritation and can accumulatein the water and air surrounding treated recreational water venues. In drinking water treatment, monochloramine is used for disinfection to reduce formation of disinfection by-products created when using chlorine as a disinfectant (see combined chlorine level).

coliforms All aer obic and facultative anaerobic, gram-negative, nonspore-forming, rod-shaped bacteria that ferment lactose with gas formation within 48 hours at 95oF (35oC).

combined chlorine level See chloramines. Chlorine that has combined with organic compounds in the water and is no longer an effective disinfectant for recreational water. This value is derived by subtracting the free chlorine test level from total chlorine test level. The combined chlorine level is likely to include combined compounds in addition to chloramines.

contact time The length of time water (and pathogens) is exposed to a disinfectant, usually measured in minutes (e.g., chlorine contact time).

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### Cryptosporidium The taxonomy of Cryptosporidiumhas evolved as a result of advancements in molecular methodology and genotyping. The former C. parvumnow refers to a species that is zoonotic and infects ruminants and humans. C. hominis refers to the species of Cryptosporidiumthat infects only humans, primates, and monkeys. Both species were referred to previously as C. parvum

. dermatitis Infl ammation of the skin. In this Surveillance Summary, the term dermatitis is used to denote a broad category of skin-related symptoms (e.g., folliculitis, cellulitis, burns, or rash). disinfection by-products Chemicals formed in water through reactions between organic matter and disinfectants. Includes chloramines, also known as combined chlorines. etiologic agent The pathogen, chemical, or toxin causing a waterborne disease or outbreak. Infectious etiologic agents include bacteria, parasites, and viruses.

fecal coliforms Coliforms that grow and ferment lactose to produce gas at 112.1oF (44.5oC) within 24 hours. fill-and-drain pools Small pools, often constructed of plastic, which might be inflatable, and filled with tap water without any ongoing chemical disinfection or filtration. Sometimes called kiddie pools.

filtration The process of removing suspended particles from water by passing it through one or morepermeable membranes or media of limited pore diameter (e.g., sand, anthracite, or diatomaceous earth).

folliculitis Inflammation of hair follicles. Spa-associated folliculitis is usually associated with infection by Pseudomonas aeruginosa

. free chlorine The chlorine in water not combined with other constituents; therefore, it is able to serve as an effective disinfectant (also referred to as free available chlorine or residual chlorine). Measuring the free chlorine level is a common water-quality test. freshwater (untreated water) Surface water (e.g., water from lakes, rivers, or ponds) that has not been treated in any way to enhance its safety for recreational use.

interactive fountain A fountain or water spray device intended for (or accessible to) recreational use. They usually do not have standing water as part of the design. These are sometimes called spray pads, splash pads, wet decks, or spray grounds. In contrast, noninteractive (ornamental) fountains intended for public display rather than recreational use are often located in front of buildings and monuments, and their water is not easily accessible for public use.

marine water Untreated recreational water at an ocean or estuarine setting.
microcystin toxin A secondary metabolite of blue-green algae (cyanobacteria) that can have toxic effects onhumans and animals, potentially causing a wide range of illness or even death when exposure to accumulated toxins in fresh or marine water occurs. mixed agent outbreak More than one type of etiologic agent is identified in clinical specimens from affected persons, and each etiologic agent is found in >5% of positive clinical specimens (e.g., an outbreak with Giardia spp. [parasites] and Salmonella spp. [bacteria], with each agent identified in >5% of stool specimens).

oocyst The infectious stage of Cryptosporidiumspecies and certain other coccidian parasites with a protective wall that facilitates survival in water and other environments and renders the parasite extremely resistant to chlorine.

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### predominant illness The type of illness most commonly expressed in a substantial proportion (>50%) of patients (e.g., gastroenteritis, dermatitis, and acute respiratory illness). When more than one illness type seems to define the character of the waterborne disease and outbreak, they are listed together as predominant illnesses.

recreational water venue A body of water used for the purpose of recreation (e.g., swimming, soaking, or athletics), including any structure that encloses this water. It can include lakes and ponds, rivers, springs, the ocean, and man-made venues (e.g., swimming pools, spas, and water parks) that do not necessarily include standing water (e.g., interactive fountains). reservoir, impoundment An artificially maintained lake or other body of water created for the collection and storage of water. This body of water might be available for recreational use. setting Location where exposure to contaminated water occurred (e.g., swimming beach, water park, and hotel).

spa Any structure, basin, chamber, or tank (located either indoors or outdoors) containing a body of water intended to be used for recreational or therapeutic purposes that usually contains a waterjet or aeration system. It is operated at high temperatures and is usually not drained, cleaned, or refilled after each use. It sometimes is referred to as a hot tub or whirlpool. spray park A recreational water venue solely consisting of multiple interactive fountains.

total chlorine A common water-quality test that measures the chlorine in water that is free for disinfection (free chlorine) plus that combined with other organic materials (combined chlorine). The combined chlorine level is derived by subtracting the free chlorine test result from the total chlorine test result.

total coliforms Nonfecal and fecal coliforms that are detected by using a standard test.

treated water Water that has undergone a disinfection or treatment process (e.g., chlorination and filtration) for the purpose of making it safe for recreation. Typically, this refers to any recreational water in an enclosed, manufactured structure but might include swimming or wading pools, fountains, or spas filled with treated tap water (e.g., small wading kiddie pool) or untreated water (e.g., mineral spring water) that receives no further treatment. turbidity A measurement of suspended particulate matter in water expressed as nephelometric turbidity units (NTU).

turnover rate The time required to theoretically recirculate the entire volume of water in a swimming pool, spa, or hot tub. ultraviolet light The segment of the light spectrum between 100-300 nanometers (nm). ultraviolet light disinfection unit A device that produces ultraviolet light between 250-280 nm for the purpose of inactivation of microorganisms by UV radiation.

untreated water Surface water that has not been treated or disinfected in any way (i.e., lakes, rivers, oceans, and reservoirs).

user Any person using a pool, spa, or hot tub and adjoining deck area.

Vibrio species A genus of comm a-shaped, gram-negative Proteobacteria that include various human pathogens. Certain species are found in salty or brackish water and can cause illness by contamination of a wound or epithelial site (e.g., eardrums or sinus cavities). Sequelae can include sepsis and death.

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### waterborne-disease outbreak Water exposure in which two or more persons have been epidemiologically linked to recreational water by location of exposure, time, and illness.

waterborne disease and outbreak The surv eillance system that contains the outbreaks and case reports reported by jurisdictional surveillance system (WBDOSS) public health authorities. Inputs into this system are illustrated in Figure 1.

WBDOSS Surveillance Summary The biennial summaries of waterborne-disease outbreaks and cases associated with recreational water, drinking water and water not intended for drinking are published in the MMWR. These publications also discuss waterborne-disease data from other surveillance systems (e.g., Vibrio ) and disseminate waterborne-disease prevention messages. water-quality indicator A microbial, chemical, or physical parameter that indicates the potential risk for infectious diseases associated with using the water for drinking, bathing, or recreational purposes. The best indicator is one with a density or concentration that correlates best with health effects associated with a type of hazard or pollution (e.g., turbidity, coliforms, fecal coliforms, Escherichia coli , enterococci, free chlorine level).

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# Appendix B Descriptions of Selected Waterborne Disease and Outbreaks Associated with Recreational Water Use

**State in No. of**  **which WBDO cases**  **Date occurred Etiologic agent (deaths)**  **Description of WBDO Bacteria**  July 2005 Wyoming Campylobacter jejuni 6 Two families celebrated a holiday weekend together at a private residence. A small pool was set up for the adults and treated with a jug of bleach. A fill-and-drain pool (kiddie pool) was set up for the children and filled with untreated well water. A dog known to roll around in cow feces might have introduced fecal matter into the children’s pool. Five children, ranging from ages 13 months–8 years, and one adult developed gastrointestinal illness. Stool specimens from two of the children tested positive for Campylobacter

. July 2005 California Leptospira spp. 3 Three men became ill and were diagnosed with laboratory-confirmed leptospirosis after removing brush and picking berries in a stream near their homes. The stream was very low and slow-flowing at the time of exposure.

November 2005 Florida Leptospira spp. 43 Racers from approximately 30 U.S. states and two Canadian provinces were exposed to surface water from multiple sources, including creeks, swamps, and a river during an endurance race. In all, 192 (96%) of the racers were interviewed to collect information about exposures and signs and symptoms of illness. Mean incubation times were similar for suspected cases (12.8 days) and confirmed cases (13.5 days). The most common symptoms reported were fever (100%), headache (91%), chills (69%), sweats (68%), and muscle/joint pain (68%). Swallowing river and swamp water and being submerged were significantly associated with developing illness.

January 2006 Florida Legionella 11 (1) Eleven persons became ill (3 confirmed Legionnaires’ disease and pneumophila serogroup 1 eight atypical pneumonia cases) after staying at a hotel. A casecontrol study was conducted and revealed that only exposure to the hotel’s indoor spa was a significant risk factor for developing illness. Environmental samples did not yield Legionella. However, several deficiencies were noted during the investigation, including suboptimal water temperatures and stagnation and sediment within the hot-water system. Bromine levels in the indoor spa were measured at 0.5 ppm at the time of investigation.

January 2006 Illinois Legionella spp. 43 (1) Forty-three persons became ill (three confirmed Legionnaires’ disease and 40 Pontiac fever cases) following a hotel stay. A retrospective cohort study was conducted; exposure to the pool area was a significant risk factor for developing illness. L. pneumophila and L. maceachernii were isolated from water samples of both the pool and spa. No disinfectant residual was found in the pool or spa water.

July 2006 California Shigella sonnei 9 Five families attended a party at a private residence. A fill-and-drain pool was filled with tap water with no additional treatment. Shigella sonnei was isolated from stool samples submitted by six attendees. A retrospective cohort study revealed a significant association between pool use and subsequent illness.

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**State in No. of**  **which WBDO cases**  **Date occurred Etiologic agent (deaths)**  **Description of WBDO**
**Viruses** May 2006 Wisconsin Norovirus 18 A total of 18 persons developed gastrointestinal illness after using a hotel swimming pool and spa; three patients’ stool specimens tested positive for norovirus. A case-control study showed a significant association between spa and/or pool use and illness. The pool had a high bather load, and an ill person had used the pool. Water testing records revealed inadequate disinfection during the time of suspected exposure. The hotel was advised to close the facilities and either hyperchlorinate or drain and refill them.

**Parasites**
June 2005 Florida Cryptosporidium spp. 47 This outbreak affected persons who played in or attended a youth sports tournament. Two teams with players who had gastrointestinal illness stayed in the same hotel. Although no pool water was tested for Cryptosporidium , swimming was the only risk factor significantly associated with illness. As a result of the investigation, the hotel was advised to keep daily maintenance logs for the swimming area.

June 2005 New York C. hominis 2,307 An outbreak of gastrointestinal illness was traced to a water park with an interactive fountain. Stool samples for 495 of 572 people were positive for Cryptosporidium spp. Typing of 147 isolates identified them as C. hominis , indicating human contamination. The venue used chlorine and rapid sand filtration. Water samples collected from two tanks on three dates in mid-August contained C. hominis oocysts. C. hominis oocysts were also identified in a water filter and effluent from a sewer pump station. Polymerase chain-reaction tests were conducted on one water sample from each tank. The samples both contained 150 oocysts/L. Investigators determined that multiple factors contributed to the outbreak, including an inadequate recirculation design in which some water bypassed treatment and filtration as a result of the demand of the fountain.

July 2005 Oregon C. parvum 20 A cohort study was conducted after two confirmed and 15 suspected cases of cryptosporidiosis were reported to a local health department. Gastrointestinal illness was epidemiologically linked with swimming in a pool at a membership club. A child with laboratory-confirmed cryptosporidiosis swam in the pool during the days that water contamination was suspected to have occurred. Control measures were quickly implemented and included hyperchlorination at the membership club pool, hyperchlorination of area public pools, and posting of signs at multiple pools to discourage swimming by ill individuals; prevention messages were disseminated by local media.

July 2005 Massachusetts Giardia intestinalis 11 An outbreak at an athletic club implicated three outdoor pools (one adult pool and two children’s pools) with a shared filtration system. All 11 cases were laboratory confirmed. Although not observed, the occurrence of a fecal accident was strongly suspected. Records did not indicate that disinfectant levels were adjusted or that the pools were closed when chlorine readings were below recommended levels in early August. A water sample taken during the investigation revealed indicator bacteria (coliforms and E. coli ) levels above allowable limits.

July 2005 Oklahoma Naegleria fowleri 2 (2) Postmortem clinical specimens from two boys who died several days after they became ill indicated that they were infected with N. fowleri. Although both of the boys had spent time at a local water park before becoming ill, at least one child went swimming in untreated, stagnant water near his home before becoming ill. The boys’ homes were not far apart from each other. Water samples from a local creek and thewater park’s spray deck were collected in July and August, respectively. Testing of cultures from both locations did not detect N. fowleri

. PCR testing of the creek water was also negative. Water testing revealed temperatures >95°F (35°C) at both locations.

### 36 **MMWR September 12, 2008** 

**State in No. of**  **which WBDO cases**  **Date occurred Etiologic agent**  **(deaths) Description of WBDO** 

August 2005 Ohio C. hominis 523 A large, communitywide cryptosporidiosis outbreak affected 747 persons in Ohio. Recreational water exposure was associated with 70% (523/747) of the cases. This outbreak was linked by time and proximity to a cryptosporidiosis outbreak in Kentucky. Six pools were implicated as a source of exposure to contaminated water. More than 300 stool samples tested positive for Cryptosporidium. CDC performed additional molecular characterization of the Cryptosporidium isolates from one pool filter sand sample from the water park and seven clinical stool specimens; the subtype of the isolates of six of the stool specimens matched the pool filter sample’s isolate.

July 2006 California Cryptosporidium spp. 16 This outbreak was initially detected by a laboratory-based active cryptosporidiosis surveillance system. Some of the case-patients shared a common exposure at a public park with an interactive fountain. A 10 L sample from the fountain system contained 137 oocysts/L and had a chlorine residual of 0.9 ppm. The fountain used a sand filtration system that was not designed to remove Cryptosporidium spp. and did not have an automated disinfection system. Similar public fountains in the area were closed if they had inadequate filtration and disinfection. Ill children were restricted from attending school and daycare to limit possible person-to-person transmission.

July 2006 Illinois C. hominis 65 Attendees of a private day camp developed gastrointestinal illness that was epidemiologically linked to recreational swimming at a private day camp pool and at a public outdoor water park. A total of seven laboratory-confirmed cases and 58 probable cases were identified. PCR detected C. hominis in stool specimens from three patients. Aninspection of the day camp pool revealed poor water quality, unsanitary pool facilities and an absence of policies intended to prevent disease transmission; however, Cryptosporidium was not detected in a sample of pool water. Pool water from the water park met state guidelines for water quality but tested positive for C. parvum. Fecal accidents were reported in both pools. All areas of the water park shared one filtration and treatment system; outbreak prevention recommendations for the water park included installation of ultraviolet (UV) disinfection, as well as education for the staff and the public. ( **Source:** CDC. Cryptosporidiosis outbreaks associated with recreational water use—five states, 2006. MMWR 2007; 56:729–32).

August 2006 Colorado Cryptosporidium spp. 12 Certain persons developed cryptosporidiosis after attending a party at a community recreational center with a pool that had UV disinfection in addition to chlorination and rapid sand filtration. Swimming, swallowing water, and getting water in the mouth were significant risk factors. Pool use by diaper-aged children and the use of combined filtration systems for the adult and child pools were suspected to have been contributing factors in the outbreak. ( **Source:** CDC. Cryptosporidiosis outbreaks associated with recreational water use—five states, 2006. MMWR 2007;56:729–32).

**Chemicals/Toxins** June 2005 Michigan Copper sulfate 3 A local resident treated a state lake with copper sulfate to prevent swimmer’s itch by controlling snail populations. The pesticide wasapplied without a permit; the quantity was 30 times the labelrecommended amount for algae treatment and three times the labelrecommended amount for snail control. Subsequently, three children who spent time near or in the lake developed respiratory symptoms, and one was hospitalized. A water test conducted within 1–2 months of the pesticide application did not find hazardous levels of copper sulfate in the water.

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**State in No. of**  **which WBDO cases**  **Date occurred Etiologic agent (deaths)**  **Description of WBDO** July 2005 Ohio Chlorine gas 19 A chlorine surge at a community pool caused illness in 19 persons. The majority of swimmers were children. The predominant symptoms were breathing difficulties, cough, sore throat, and eye irritation. The recirculation pump failed, but chemical feed pumps continued to feed chlorine and acid. When the mechanical pump was restarted, a concentrated surge of chlorine gas created by the mixing of the concentrated hypochlorous acid and chlorine was introduced into the pool. The facility responded to the event by installing an electrical interlock that would automatically stop the flow of chemicals if the recirculation pump failed.

**Unidentified** April 2005 Minnesota Suspected chloramines 20 A case-control study was conducted after reports of respiratory and ocular symptoms among attendees at a birthday party at a hotel pool. Multiple other symptoms were documented, including burning nose and throat, nausea, and headache; 12 case-patients sought medical care within 1 day of attending the party. Water contact and entering the pool enclosure were significantly associated with illness. The outbreak investigation determined that the chlorine levels in the pool might not have been properly maintained, record-keeping was inadequate, showering facilities in the pool area were inadequate, no pool operator was on duty, and official bather load was exceeded for the pool during the party.

July 2005 Florida Suspected jellyfish larvae 24 Attendees of a conference reported symptoms such as fever, fatigue,headache, chills, and muscle ache. Illness was significantly associated with swimming in the ocean and chlorinated resort pools. No clinical specimens were collected because symptoms had resolved before the investigation was initiated. Multiple symptoms were consistent with exposure to toxins released by minute jellyfish larvae (seabather’s eruption). Although weather patterns at the time, as well as the month of the outbreak, supported the hypothesis of seabather’s eruption, investigators concluded that certain illnesses might have occurred as a result of other etiologies. Interview data described poor pool water quality and high bather loads. An inspection of the pool facilities was conducted as part of the investigation and led to pool closure.

June 2006 Illinois Suspected low pH 9 Swimmers from two classes at a neighborhood swimming pool had burning rashes on their bodies after they left the pool. The swimmers were ages 4–8 years. The instructor, who was in the water for a total of 80 minutes, reported a similar rash on his arms. Testing indicatedthat the pool water had a low pH. The exact pH could not be determined; the lower limit for the test strip was seven. The problem was traced back to the automatic sensing unit for feeding acid, which was not working correctly.

December 2006 Nebraska Suspected chloramines 24 A child attending a family event at a motel swam for 3 hours in the indoor pool, during which time he developed respiratory symptoms. He was hospitalized overnight with severe chemical epiglottitis andlaryngotracheobronchitis. A follow-up investigation identified 24 casepatients who had developed ocular and/or respiratory symptoms after being in or near the pool. The state health department inspected the pool and closed it as a result of multiple state health code violations. Pool water pH was 3.95 (acceptable range: 7.2–7.8); the free chlorine level was 0.8 ppm (acceptable range: 2–10 ppm) and the combined chlorine level was 4.2 ppm (acceptable limit: <0.5 ppm). Pool records indicated that water quality violations had occurred frequently during a 26-day period before the outbreak. Chloramine levels might have been higher on the day that the child became ill because of inadequate ventilation; the only ceiling exhaust fan was turned off, and all of the nearby windows were closed. Although the motel was licensed by the state of Nebraska, it was a nonmunicipal public pool and, therefore, pool operators were not required to undergo training and certification. ( **Source:** CDC. Ocular and respiratory illness associated with an indoor swimming pool—Nebraska, 2006. MMWR 2007;56:929–32).

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**State in No. of**  **which WBDO cases**  **Date occurred Etiologic agent (deaths)**  **Description of WBDO**
**Vibrio infections**  August 2005 Louisiana Vibrio vulnificus 1 (1) A man aged 60 years waded for 3 days in flood waters after Hurricane Katrina in New Orleans, Louisiana, and arrived in Texas during the end of August 2005. His medical history included stroke, hypertension, and alcohol abuse. The day after he arrived in Texas, he went to an emergency department; he had ankle wounds and diarrhea. He was released after treatment but was admitted to the hospital 1 day later when Vibrio vulnificus was positively identified from a blood culture

. He died in the hospital the next day. ( **Source:** CDC. Vibrio illnesses after Hurricane Katrina—multiple states, August–September 2005. MMWR 2005;54:928–31).

August 2005 Mississippi V. parahaemolyticus 1 (1) A man aged 61 years died shortly after seeking medical treatment for V. parahaemolyticus infection; he had hypothermia and multiple second-and third–degree abrasions on his body after exposure to Hurricane Katrina flood waters. The patient was also known to have human immunodeficiency virus infection, coronary artery disease, and hyperlipidemia. ( **Source:** CDC. Vibrio illnesses after Hurricane Katrina—multiple states, August–September 2005. MMWR 2005;54:928–31).

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# Surveillance for Waterborne Disease and Outbreaks Associated with Drinking Water and Water not Intended for Drinking — United States, 2005–2006

Jonathan Yoder MSW, MPH 1

Virginia Roberts, MSPH 1,2 Gunther F. Craun, MPH 3 Vincent Hill, PhD, PE 1 Lauri Hicks, DO 4 Nicole T. Alexander, MPH 4 Vince Radke MPH 5 Rebecca L. Calderon, PhD 6 Michele C. Hlavsa, MPH 1

Michael J. Beach, PhD 1

Sharon L. Roy, MD 1
1 Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Disease, CDC 2 Atlanta Research and Education Foundation 3 Gunther F. Craun and Associates, Staunton, Virginia 4 Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, CDC 5 Division of Emergency and Environmental Health Services, National Center for Environmental Health, CDC 6

U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 

## Abstract

Problem/Condition: Since 1971, CDC, the U.S. Environmental Protection Agency (EPA), and the Council of Stateand Territorial Epidemiologists have maintained a collaborative Waterborne Disease and Outbreak Surveillance System (WBDOSS) for collecting and reporting data related to occurrences and causes of waterborne-disease outbreaks (WBDOs) and cases of waterborne disease. This surveillance system is the primary source of data concerning the scope and effects of waterborne disease in the United States. Reporting Period: Data presented summarize 28 WBDOs that occurred during January 2005–December 2006 and four previously unreported WBDOs that occurred during 1979–2002. Description of System: The surveillance system includes data on WBDOs associated with recreational water, drinking water, water not intended for drinking (WNID) (excluding recreational water), and water use of unknown intent. Public health departments in the states, territories, localities, and Freely Associated States (FAS) (i.e., the Republic ofthe Marshall Islands, the Federated States of Micronesia, and the Republic of Palau, formerly parts of the U.S.-administered Trust Territory of the Pacific Islands) are primarily responsible for detecting and investigating WBDOs and voluntarily reporting them to CDC by a standard form. Only cases and outbreaks associated with drinking water, WNID (excluding recreational water), and water of unknown intent (WUI) are summarized in this report. Cases and outbreaks associated with recreational water are reported in a separate Surveillance Summary

. Results: Fourteen states reported 28 WBDOs that occurred during 2005–2006: a total of 20 were associated with drinking water, six were associated with WNID, and two were associated with WUI. The 20 drinking water-associatedWBDOs caused illness among an estimated 612 persons and were linked to four deaths. Etiologic agents were identified in 18 (90.0%) of the drinking water-associated WBDOs. Among the 18 WBDOs with identified pathogens, 12 (66.7%) were associated with bacteria, three (16.7%) with viruses, two (11.1%) with parasites, and one (5.6%) mixed WBDO with both bacteria and viruses. In both WBDOs where the etiology was not determined, norovirus was the suspected etiology. Of the 20 drinking water WBDOs, 10 (50) were outbreaks of acute respiratory illness (ARI), nine (45%) were outbreaks of acute gastrointestinal illness (AGI), and one (5.0%) was an outbreak of hepatitis. All WBDOs of ARI were caused by Legionella , and this is the first reporting period in which the proportion of ARI WBDOs has sur- Corresponding author: Jonathan S. Yoder, MSW, MPH, Division of Parasitic 

### passed that of AGI WBDOs since the reporting of Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases, 4770 Buford Hwy., NE, MS F-22, Atlanta, GA 30341. Telephone: 770-488- 

### Legionella WBDOs was initiated in 2001. 3602; Fax: 770-488-7761. E-mail: jey9@cdc.gov.

### 40 **MMWR September 12, 2008** 



### A total of 23 deficiencies were cited in the 20 WBDOs associated with drinking water: 12 (52.2%) deficiencies fell under the classification NWU/POU (deficiencies occurred at points not under the jurisdiction of a water utility or at the point-of-use), 10 (43.5%) deficiencies fell under the classification SWTDs (contamination at or in the source water, treatment facility, or distribution system), and for one (4.3%) deficiency, classification was unknown. Among the 12 NWU/POU deficiencies, 10 (83.3%) involved Legionellaspp. in the drinking water system. The most frequently cited SWTD deficiencies were associated with a treatment deficiency (n = four [40.0%]) and untreated ground water (n = four [40.0%]). Three of the four WBDOs with treatment deficiencies used ground water sources. Interpretation: Approximately half (52.2%) of the drinking water deficiencies occurred outside the jurisdiction of a water utility. The majority of these WBDOs were associated with Legionellaspp, which suggests that increased attention should be targeted towards reducing illness risks associated with Legionella spp. Nearly all of WBDOs associated with SWTD deficiencies occurred in systems using ground water. EPA’s new Ground Water Rule might prevent similar outbreaks in the future in public water systems.
Public Health Actions: CDC and EPA use surveillance data to identify the types of water systems, deficiencies, andetiologic agents associated with WBDOs and to evaluate the adequacy of current technologies and practices for providing safe drinking water. Surveillance data also are used to establish research priorities, which can lead to improvedwater-quality regulation development. The majority of drinking water deficiencies are now associated with contamination at points outside the jurisdiction of public water systems (e.g., regrowth of Legionella spp. in hot water systems) and water contamination that might not be regulated by EPA (e.g., contamination of tap water at the POU). Improved education of consumers and plumbers might help address these risk factors.



# Introduction
Statistical data on waterborne-disease outbreaks (WBDOs) in the United States have been collected since 1920. Researchers reported these statistics during 1920–36 ( 1 ), 1938–1945 (2 ), 1946–1960 (3 ), and 1961–1970 ( 4 ). Since 1971, CDC, theU.S. Environmental Protection Agency (EPA), and the Council of State and Territorial Epidemiologists (CSTE) have maintained a collaborative Waterborne Disease and Outbreak Surveillance System (WBDOSS), which tracks the occurrences and causes of WBDOs and cases of disease associated with drinking water. The history of WBDO surveillance in the United States is summarized in the 2003–2004 WBDOSS Surveillance Summary ( 5 ). The 2005–2006 Surveillance Summary presents data on 28 WBDOs reported by public health departments in the states, territories, and localities thatoccurred during January 2005–December 2006, and four previously unreported WBDOs that occurred during 1979–2002. However, the statistics in this report represent only a portion of the burden of illness associated with water exposure. They do not include endemic waterborne-disease cases (sporadic cases not known to be associated with a WBDO), WBDOs associated with recreational water use, or reliable estimates of the number of unrecognized WBDOs. 

# Background U.S. Environmental Protection Agency Drinking Water Regulations

The majority of WBDOs reported in this Surveillance Summary occurred in public drinking water systems. The Safe Drinking Water Act (SDWA) of 1974 and its subsequent 1986 and 1996 amendments (Table 1) authorize EPA to set national standards to protect public drinking water and its sources against naturally occurring or man-made contaminants ( 6–8). EPA has set health-based standards for approximately90 chemical, microbiologic, radiologic, and physical contaminants in drinking water. Standards include a maximum contaminant level* (amount of a contaminant allowed in water delivered to the consumer) or treatment technique (required procedure or level of technological performance) that apply to systems providing water to at least 15 service connectionsor 25 persons for at least 60 days in a year (Public Water Systems). EPA also has recommended guidelines (Secondary Drinking Water Regulations), for water contaminants that primarily affect the aesthetic qualities of drinking water (e.g., taste, odor, and staining of laundry) that states may choose to adopt and enforce. EPA regulations and guidelines do notapply to private, individual water supplies (Figure 1); however, certain states set standards for individual water supplies.

* Additional terms have been defined (Appendix A, Glossary of Definitions).

### 41 **Vol. 57 / SS-9 Surveillance Summaries** 

**TABLE 1. U.S. Environmental Protection Agency regulations regarding drinking water, by year enacted — United States,**  **1974–2006 Regulation**  **Year** Safe Drinking Water Act (SDWA) 1974 Interim Primary Drinking Water Standards 1975 National Primary Drinking Water Standards 1985 SDWA Amendments 1986 Surface Water Treatment Rule (SWTR) 1989 Total Coliform Rule 1989 Lead and Copper Regulations 1990 SDWA Amendments 1996 Information Collection Rule 1996 Interim Enhanced SWTR 1998 Disinfectants and Disinfection By-Products (D-DBPs) Regulation 1998 Contaminant Candidate List 1998 Unregulated Contaminant Monitoring Regulations 1999 Lead and Copper Rule — action levels 2000 Filter Backwash Recycling Rule 2001 Long Term 1 Enhanced SWTR 2002 Unregulated Contaminant Monitoring Regulations 2002 Drinking Water Contaminant Candidate List 2 2005 Long Term 2 Enhanced SWTR 2006 Stage 2 D-DBP Rule 2006 Ground Water Rule 2006



### Public and individual water system types and subtypes have been defined (Appendix A, Glossary of Definitions).

Standards by which microbial contamination is regulated include the Total Coliform Rule (TCR) ( 9,10), Ground Water Rule (GWR) ( 11,12), Wellhead Protection Program ( 11 ), Surface Water Treatment Rule (SWTR) ( 13 ), Interim Enhanced SWTR ( 14 ), Long Term 1 Enhanced SWTR ( 15 ), Long Term 2 Enhanced SWTR ( 16–18), Stage 2 Disinfectants and Disinfection By-products Rule ( 16, 17 ), and Filter Backwash Recycling Rule ( 19). EPA’s lead, copper, and arsenic rules prescribe action levels at which a system operator must take corrective steps ( 20,21 ). In addition, EPA is required to publish periodically a list of contaminants that might need to be regulated (22,23 ) and establish criteria for a program to monitor unregulated contaminants (24–27 ). EPA decides whether or not to regulate contaminants on the listbased on projected adverse health effects from the contaminant, an assessment of the extent of occurrence of the contaminant in drinking water, and the potential for reducingrisks to health. Instead of a regulation, EPA can issue guidance or a health advisory. All of these requirements have been described in previous Surveillance Summaries ( 5,28). In 2007,EPA established an advisory committee to provide recommendations on revisions to the TCR and on information needed to better understand the public health risks associated with the degradation of water quality in pipes, storage tanks, andother appurtenances used to distribute drinking water to consumers (29 ). 

# Methods
Data Sources

Public health departments in the states, territories, localities,and FAS have primary responsibility for detecting and investigating WBDOs, which they report voluntarily to CDC using a standard form (CDC form 52.12, available at http://www. cdc.gov/healthyswimming/downloads/cdc_5212_ waterborne.pdf) . The form solicits data on characteristics of WBDO (e.g., number of cases, time, and location); results from epidemiologic studies; results from clinical specimen andwater sample testing; and other factors potentially contributing to WBDO (e.g., environmental conditions, disinfection deficiencies, and filtration problems). CDC annually requestsreports of WBDOs and single cases of certain waterborne diseases, as specified in the definitions in the next section, fromstate, territorial, and FAS epidemiologists or persons designated as WBDO surveillance coordinators and obtains additional information regarding water quality and water treatment as needed. In certain instances, information on WBDOs and cases is solicited from other CDC surveillance systems and confirmed with the state or locality for inclusion in WBDOSS and/or Surveillance Summary , which is illustrated in more detail in a separate Surveillance Summary (30 ). Numerical andtext data are abstracted from WBDO report form and supporting documents and entered into a database for analysis. Although reports of WBDOs are collected through WBDOSS, the cases and outbreaks associated with drinking water, water not intended for drinking (WNID), and water of unknown intent (WUI) are analyzed and published separately from the cases and outbreaks associated with recreational water (30 ).



## Definitions

WBDOSS collects data on both outbreaks and individual cases of waterborne disease. Two criteria must be met for anevent to be defined as a waterborne-disease outbreak associated with drinking water, WNID (excluding recreationalwater), or WUI. First, two or more persons must be epidemiologically linked by location of exposure to water, and by time, and characteristics of illness. Second, the epidemiologic evidence must implicate water as the probable source of illness.

In addition to WBDOs, single cases of laboratory-confirmed primary amebic meningoencephalitis (PAM) as a result of Naegleria fowleri infection with a known water exposure and single cases of chemical/toxin poisoning, if water-quality data indicate contamination by the chemical/toxin, are also reported in WBDOSS. All single cases are discussed separately from WBDOs. Single cases of legionellosis are reported elsewhere ( 31 ).

### 42 **MMWR September 12, 2008** 

**FIGURE 1. Types of drinking water systems — United States**

Drinking Water Systems

Public Water Systems Public or private ownership (subject to EPA* regulations) Individual Water Systems (if regulated, state or local regulations)

Noncommunity Community Use of nonpublic sources

Transient (e.g., gas stations, parks, resorts,

campgrounds, restaurants, and motels with their own water systems)

Nontransient (e.g., schools, factories, office buildings, and hospitals with their own water systems) Privately owned home or farm wells, springs, or surface water sources

Streams, ponds, or shallow wells not intended for drinking

Bottled water (commercially bottled water is

regulated by FDA † ; persons might also fill their own containers) §

* U.S. Environmental Protection Agency. † Food and Drug Administration. § In certain instances, bottled water is used in lieu of a community supply or by noncommunity systems.



### Reported outbreaks associated with contaminated drinking water; commercially bottled water, ice, or beverages made with contaminated water; and water contaminated by malfunctions in equipment/devices in which water is used or distributed (e.g., beverages contaminated by plumbing failures in drink mix/soda machines) are classified as WBDOs. Tabulation of WBDOs is based on location of water exposure, not on state of residence of the ill persons. WBDOs associated with cruise ships are not summarized in this report.

Of the approximately 155,693 public water systems in the United States, 52,110 (33.5%) are community systems and 103,583 (66.5%) are noncommunity systems, including 84,744 transient systems and 18,839 nontransient systems. Community systems serve 286.5 million persons, and only8% of these systems provide water to 82% of the U.S. population through large municipal water systems (32). Noncommunity, nontransient systems provide water to 6.3 million persons, and noncommunity, transient systems provide water to 13.8 million persons (by definition, these populations also use another type of water system at their residences, except forthe limited number of permanent residents of nontransient systems) (32 ). Although the majority of public water systems (91%) are supplied by ground water, more persons (68%) are supplied year-round by community water systems that use surface water (32 ). Approximately 15.0% of the U.S. population relies on individual water systems that are privately owned (33).

WBDOs associated with commercially bottled water are classified separately from the water systems described in this Surveillance Summary . Separating piped from nonpiped water distinguishes between drinking water systems regulated by EPA (community and noncommunity) and the Food and Drug Administration (FDA) (bottled).

The purpose of WBDOSS is not only to evaluate the relation between water and reported disease outbreaks and cases, but also to identify system breakdowns, operator errors, other engineering-related activities, and environmental situations that lead to outbreaks. To understand the circumstances andsystem breakdowns that lead to illness, each WBDO is classified as having one or more deficiencies (Table 2).



## Waterborne Disease and Outbreak Strength of Evidence Classification

All WBDOs reported to the surveillance system have beenclassified according to the strength of the evidence implicating water as the vehicle of transmission (Table 3). The classification scheme (i.e., Classes I–IV) is based on the epidemiologic and water-quality data provided with WBDO report form. Although WBDOs without water-quality datawere included in this report, reports that lacked epidemiologic data, linking the outbreak to water, have been excluded.

A classification of I indicates that adequate epidemiologicand water-quality data were reported. However, this classification does not necessarily imply that the investigation was conducted optimally nor does a classification of II, III, or IV imply that the investigation was inadequate or incomplete.

### 43 **Vol. 57 / SS-9 Surveillance Summaries** 

**TABLE 2. Deficiency classification for drinking water, water not intended for drinking (excluding recreational water), and wate r of**  **unknown intent Deficiency**  **Contamination of water at/in the water source, treatment facility, or distribution system (SWTD)*** 1: Untreated surface water intended for drinking 2: Untreated ground water intended for drinking 3: Treatment deficiency (e.g., temporary interruption of disinfection, chronically inadequate disinfection, inadequate or no fil tration) 4: Distribution system deficiency, including storage (e.g., cross-connection, backflow, contamination of water mains during construction or repair) 13: Current treatment processes not expected to remove a chemical contaminant (e.g., pesticide contamination of groundwater treated with disinfection only) A: Surface water B: Ground water **Contamination of water at points not under the jurisdiction of a water utility or at the point of use (NWU/POU) †**  5: Legionella spp. in water system A: Water intended for drinking B: Water not intended for drinking (excluding recreational water) C:Water of unknown intent 6: Plumbing system deficiency after the water meter or property line (e.g., cross-connection, backflow, corrosion products) 7: Deficiency in building/home-specific water treatment after the water meter or property line 8: Deficiency or contamination of equipment using or distributing water (e.g., drink-mix machines) 9: Contamination or treatment deficiency during commercial bottling 10: Contamination during shipping, hauling, or storage A: Water intended for drinking – Tap water B: Water intended for drinking – Commercially bottled water 11: Contamination at point-of-use A: Tap B: Hose C:Commercially bottled water D:Container, bottle, or pitcher E: Unknown 12: Drinking or contact with water not intended for drinking (excluding recreational water)
**Unknown/Insufficient Information** 99: Unknown/Insufficient information A: Water intended for drinking – Tap water B: Water intended for drinking – Commercially bottled water C:Water not intended for drinking (excluding recreational water) D:Water of unknown intent * Contamination of water and deficiencies occurring in the drinking water system at/in the water source, treatment facility, or distribution system of pipes

and storage facilities. For a community water system, the distribution system refers to the pipes and storage infrastructure under the jurisdiction of the water utility before the water meter or property line (if the system is not metered). For noncommunity and nonpublic individual water systems, the distribution system refers to the pipes and storage infrastructure before entry into a building or house (e.g., in a service li ne leading to a house or building). † Contamination of drinking water and deficiencies occurring in plumbing and pipes that are not part of the distribution system or at other points outside

the jurisdiction of a water utility. For community systems, this means after the water meter or property line (if the system is not metered), and for noncommunity and nonpublic systems, this means within the building or house (e.g., in the plumbing inside a house or building). This category also includes contamination during shipping or hauling, during storage other than in the distribution system, and at point-of-use).



### WBDOs and their resulting investigations occur under dif- Deficiencies ferent circumstances, and not all WBDOs can be rigorously One deficiency, 13, has been added to the deficiency classifi­ investigated. In addition, WBDOs that affect few persons are cation table (Table 2). This deficiency will allow for the classifi­ more likely to receive a classification of III or IV because of cation of chemical contamination of source water when the the limited sample size available for epidemiologic analysis. existing treatment provided for the system is not designed to remove that chemical contamination. WBDOs associated with 

## Changes in the 2005–2006 Surveillance chemical contamination of untreated source water will 

## Summary continue to be reported under deficiencies 1 or 2 as appropriate.

Definitions and deficiencies in this report have been modified to Definition better reflect the epidemiology of WBDOs and capture the scope The definition of a waterborne disease outbreak (WBDO) of water-related disease. This section highlights those changes. has been modified to include only water exposure in which more than two persons become ill. Single cases of PAM and

### 44 **MMWR September 12, 2008** 

**TABLE 3. Classification of investigations of waterborne disease and outbreaks based on strength of evidence implicating water as a vehicle of transmission — United States, 2005–2006**  **Class Epidemiologic data**  **Water-quality data**
I Adequate Provided and adequate Data provided concerning exposed and unexposed persons, Laboratory data or historical information (e.g., reports of a with relative risk or odds ratio > 2 or p < 0.05 chlorinator malfunction, a water main break, no detectable free-chlorine residual, or the presence of coliforms in the water)

II Adequate Not provided or inadequate (e.g., laboratory testing of water not conducted and no historical information)

III Provided but limited Provided and adequate Epidemiologic data provided that did not meet the criteria for Class I, or claim made that ill persons had no exposures in common besides water but no data provided

IV Provided but limited Not provided or inadequate



### illnesses caused by exposure to chemically-contaminated water will continue to be included in WBDOSS but will notbe classified or analyzed as outbreaks. This change will provide a consistent outbreak definition of two or more persons epidemiologically linked by location of exposure to water, and by time, and characteristics of illness.



# Results During 2005–2006, a total of 14 states reported 28 WBDOs (i.e., 13 for 2005 and 15 for 2006). These WBDOs were associated with drinking water (n = 20), WNID (n = six), and WUI (n = two) and are tabulated by year and state (Tables4–6). Four previously unreported WBDOs that occurred during 1979–2002 also were reported (Table 7).



## Waterborne Disease and Outbreaks Associated with Drinking Water

The 20 drinking water-associated WBDOs (i.e., eight in 2005 and 12 in 2006) were reported by 11 states (Figure 2). Multiple etiologic agents were implicated (Figure 3), and WBDOs occurred throughout the year (Figure 4). Selected descriptions of WBDOs are presented (Appendix B).

The 20 drinking water-associated WBDOs reported during 2005–2006 caused illness among at least 612 persons and resulted in four deaths. The median number of persons affected in a WBDO was 10 (range: two–148). One WBDO was associated with hepatitis A. The remaining WBDOs were associated with either acute gastrointestinal illness (AGI) oracute respiratory illness (ARI). All ARI outbreaks were associated with exposure to Legionella spp. (Figure 5). Four (20.0%) of the 20 drinking water-associated WBDOs were given a strength of evidence Class I ranking on the basis of epidemiologic and water-quality data; two (10.0%) were ranked as Class II; 13 (65.0%) were ranked as Class III; and one (5.0%) was ranked as Class IV. Drinking waterassociated WBDOs are tabulated by etiologic agent and type of water system (Table 8), etiologic agent and type of water source (Table 9), type of deficiency and type of water system (Table 10), type of deficiency and type of water source (Table 11), predominant illness and type of water system (Table 12), and predominant illness and type of water source (Table 13). WBDOs were included (Tables 8–13) only if the type of deficiency might be relevant in the cause of WBDO (e.g., understanding the source of raw untreated water isunlikely to be important for a legionellosis outbreak associated with a building plumbing system). Etiologic Agents

Of the 20 drinking water-associated WBDOs, 12 (60.0%) were caused by bacteria, three (15.0%) were caused by viruses, two (10.0%) were caused by parasites, and one (5.0%) was caused by more than one etiologic agent type. Two (10.0%) were of unknown etiology (Figure 6).

Bacteria. Twelve WBDOs affecting 135 persons were attributed to bacterial infections: 10 outbreaks caused by Legionella ; one outbreak caused by Campylobacter; and one outbreak (Oregon, 2005) in which persons had multiple stool specimens that tested positive for C. jejuni
, Escherichia O157:H7, and E. coli O145. Illnesses from these 12 WBDOs resulted in four deaths, all of which were associated with Legionella spp. Viruses. Three WBDOs affecting 212 persons were attributed to viral infections: two outbreaks caused by norovirus G1, and one outbreak caused by hepatitis A. No deaths were reported.

Parasites. Two WBDOs affecting 51 persons were attributed to parasites: one outbreak caused by Giardia intestinalis and one outbreak caused by Cryptosporidium . No deaths were reported.

### 45 **Vol. 57 / SS-9 Surveillance Summaries** 

**TABLE 4. Waterborne-disease outbreaks associated with drinking water (n = eight), by state — United States, 2005**

**State Month**  **Class Etiologic agent**  **Predominant illness** * **No. of cases (deaths)**  **† (n = 180)**  **Type of system**  **§ Deficiency** **¶ Water** 

**source Setting**  California Florida

New York New York New York Ohio Oregon

Pennsylvania Aug Nov

Dec Dec Dec Aug May

Nov II IV

III III III I III

III Giardia intestinalis Legionella pneumophila serogroup 1 L. pneumophila serogroup 6 L. pneumophila serogroup 6 L. pneumophila serogroup 1 Unidentified §§ Escherichia coli O157:H7 Campylobacter jejuni, and E. coli O145*** L. pneumophila serogroup 1 AGI ARI

ARI ARI ARI AGI AGI

ARI 41 2

2 8 4 (1)

59 60

4 Unknown Unknown**

Com Com Com Ncom Ncom

Ncom 11D 5A

5A 5A 5A 3 3

5A Unknown Unknown ††

Lake †† Lake †† Lake †† Spring River

Unknown †† Gym Senior housing center Hospital Hospital Hospital Restaurant ¶¶ Camp

Long-term–care facility * AGI: acute gastrointestinal illness; and ARI: acute respiratory illness. † Deaths are indicated in parentheses if they occurred. § Com: community; and Ncom: noncommunity. Community and noncommunity water systems are public water systems that have >15 service connections or serve an average of >25 residents for >60 days/year. A community water system serves year-round residents of a community, subdivision, or mobile home park. A noncommunity water system serves an institution, industry, camp, park, hotel, or business and can be nontransient or transient. Nontransient systems serve >25 of the same persons for >6 months of the year but not year-round (e.g., factories and schools), whereas transient systems provide water to places in which persons do not remain for long periods (e.g., restaurants, highway rest stations, and parks). Individual water systems are small systems not owned or operated by a water utility that have <15 connections or serve <25 persons. ¶ Deficiency classification for drinking water, water not intended for drinking (excluding recreational water), and water of unkn own intent ( see Table 2). ** Senior Housing center is served by a community system with a ground water source; however, case-patients traveled together to other cities where

exposure might have occurred. †† Transmission of Legionella thought to be a result of building-specific factors and not related to water source. §§ Etiology unidentified; norovirus suspected based upon incubation period, symptoms, and duration of illness. ¶¶ Private residence was licensed to serve food. *** Nine persons had stool specimens that tested positive for E. coli O157:H7, three persons had stool specimens that tested positive for C. jejuni , two persons had stool specimens that tested positive for E. coli O145, and three persons had stool specimens that tested positive for both E. coli O157:H7 and C. jejuni

.


### Mixed agent types. One WBDO was attributed to more than one type of etiologic agent; no deaths were reported. This outbreak affected 139 persons and involved two viruses (norovirus G1 and norovirus G2) and one bacterium ( C. jejuni ) (34 ). Unidentified etiologic agents. Two WBDOs involving AGI of unidentified etiology affected 75 persons; no deaths werereported. No viral testing was attempted in one of the outbreaks (Ohio 2005). In the other outbreak (New York 2006), norovirus, enterovirus, and rotavirus were isolated from water samples. In both of the outbreaks, norovirus was thesuspected etiology on the basis of incubation period, symptoms, and duration of illness.



## Deficiencies

Twenty-three deficiencies were cited in the 20 drinking water-associated WBDOs. Ten (43.5%) deficiencies involved the source water, treatment facility, or distribution system (SWTD) and 12 (52.2%) deficiencies occurred at points not under the jurisdiction of a water utility or at the point-of-use(NWU/POU). One WBDO (4.3%) had an unknown deficiency (Figure 7; Table 14). Deficiencies 1–4 and 13: Contamination of Wa ter at/in the W ater Source, Treatment Facility, or Distribution System

Eight WBDOs were given a deficiency classification of 1–4. Three (37.5%) of these WBDOs were associated with viruses, two (25.0%) were associated with bacteria, two (25.0%) were associated with unidentified etiologic agents, and one (12.5%) was associated with mixed agent types.

Water-quality data. All eight WBDOs with a deficiency classification of 1–4 had water-quality data (e.g., laboratory data regarding the presence of coliform bacteria, pathogens,or chemical/toxin contaminants; or historical data [e.g., levels of disinfectants]). Positive total or fecal coliform results from the implicated water were reported for four (66.7%) of the six WBDOs with confirmed infectious etiologies. In two WBDOs caused by norovirus G1 and hepatitis A virus, the implicated pathogens were isolated from water in addition to fecal coliforms and E. coli

.

Water systems. Five (62.5%) of eight WBDOs with deficiencies 1–4 involved noncommunity water systems, two (25.0%) involved individual water systems, and one (12.5%) involved a community water system (Tables 8, 10, and 12; Figure 6). Among the five outbreaks involving noncommu­

### 46 **MMWR September 12, 2008** 

**TABLE 5. Waterborne-disease outbreaks associated with drinking water (n = 12), by state — United States, 2006**

**State Month**  **Class Etiologic agent**  **Predominant illness** * **No. of cases (deaths)**  **† (n = 432)**  **Type of system**  **§ Deficiency** **¶ Water** 

**source Setting** 
Indiana Maryland North Carolina New York

New York New York Ohio Ohio Oregon Pennsylvania Texas Wyoming Feb Jul Jul Aug

Jun Jan Sep Aug Dec Apr Apr Jun I III I III

III III II III III III III I Campylobacter Norovirus G1 Hepatitis A Unidentified**

Legionella †† L. pneumophila serogroup 3 Cryptosporidium L. pneumophila serogroup 1 Norovirus G1 L. pneumophila serogroup 1 L. pneumophila †† Norovirus G1, C. jejuni

, Norovirus G2 ¶¶ AGI AGI Hep AGI

ARI ARI AGI ARI AGI ARI ARI AGI 32 148

16 16

4 2 10 3 48

4 10 (3)

139 Com Ncom Ind Ind

Com Com Com Com Ncom Ncom Com Ncom 3, 4 3, 4, 11B 2 2

5A 5A 99A 5A 2 5A 5A 2 Well Well Spring Well

Lake §§ Reservoir §§ Well Lake §§ Well Well §§ Unknown §§ Well Community Camp Private residence Bed and Breakfast Hospital Hospital Church Hospital Restaurant Hotel Hospital Camp

* AGI: acute gastrointestinal illness; ARI: acute respiratory illness; and Hep: viral hepatitis. † Deaths are indicated in parentheses if they occurred. § Com: community; Ncom: noncommunity; and Ind: individual. Community and noncommunity water systems are public water systems that have >15

service connections or serve an average of >25 residents for >60 days/year. A community water system serves year-round residents of a community, subdivision, or mobile home park. A noncommunity water system serves an institution, industry, camp, park, hotel, or business a nd can be nontransient or transient. Nontransient systems serve >25 of the same persons for >6 months of the year but not year-round (e.g., factories and schools), whereastransient systems provide water to places in which persons do not remain for long periods (e.g., restaurants, highway rest stations, and parks). Individual water systems are small systems not owned or operated by a water utility that have <15 connections or serve <25 persons. ¶ Deficiency classification for drinking water, water not intended for drinking (excluding recreational water), and water of unkn own intent (see Table 2). ** Etiology unidentified; norovirus suspected based upon incubation period, symptoms, and duration of illness. Norovirus, enterovirus, and rotavirus were

isolated from the well. †† Environmental testing detected L. pneumophila serogroup 1, L. pneumophila other than serogroup 1, and non- pneumophila Legionella species. §§ Transmission of Legionella thought to be as a result of building-specific factors and not related to water source. ¶¶ Eight persons had stool specimens that tested positive for norovirus G1, six persons had stool specimens that tested positive f or C. jejuni, and three

persons had stool specimens that tested positive for norovirus G2. **Source** : CDC. Gastroenteritis among attendees at a summer camp—Wyoming, June–July 2006. MMWR 2007;56:368–70.

**TABLE 6. Waterborne-disease outbreaks associated with water not intended for drinking (WNID) (excluding recreational water) and water of unknown intent (WUI) (n = eight) — United States, 2005–2006** 

**State Water**  **type Month/**  **Year Class**  **Etiologic agent Predominant**  **illness*** **No. of cases (deaths)**  **† (n = 96) Deficiency**  **§ Primary**  **water exposure**  **Setting** California

Colorado New York

New York New York Pennsylvania South Dakota

Tennessee WNID

WNID WNID

WNID WNID WUI WNID

WUI Jul 2005

May 2006 Jul 2005

Jan 2006 Aug 2006 Jul 2005 May 2005

Aug 2005 IV

II III

III III IV I

II Giardia intestinalis

G. intestinalis Legionella pneumophila serogroup 1 L. pneumophila serogroup 1 L. pneumophila serogroup 1 L. pneumophila serogroup 1 L. pneumophila serogroup 1 ¶

Escherichia coli O157:H7 AGI

AGI ARI

ARI ARI ARI ARI

AGI 3

6 22 (3)

2 28 (3) 3 18 (1)

14 12

12 5B

5B 5B 5C 5B

99D Canal

River Cooling tower

Cooling tower Cooling tower Unknown Decorative fountain Unknown** Private residence Wilderness Hospital

Hospital Nursing home Hotel Restaurant

Sports camp * AGI: acute gastrointestinal illness; and ARI: acute respiratory illness. † Deaths are indicated in parentheses if they occurred. § Deficiency classification for drinking water, water not intended for drinking (excluding recreational water), and water of unkn own intent (see Table 2). ¶ **Source:** O’Loughlin RE, Kightlinger L, Werpy MC **,** et al. Restaurant outbreak of Legionnaires’ disease associated with a decorative fountain: an

environmental and case control study. BMC Infect Dis 2007; 7:93. ** Illnesses were associated with attendance at a tennis camp and swimming in an outdoor pool at the camp. Fecal contamination was detected in

nonpotable well water delivered to outdoor faucets located at multiple locations around the tennis courts. Faucets were intended for irrigation, but no signs were posted to warn the public about nonpotable water.

### 47 **Vol. 57 / SS-9 Surveillance Summaries** 

**TABLE 7. Waterborne-disease outbreaks associated with drinking water (DW) and water not intended for drinking (WNID) that were not included in previous**  **Surveillance Summaries (n = four), by state— United States, 1979–2002** 
**No. of cases Water**  **Month/ Predominant (deaths)**  **† Type of**  **Water State**  **type Year**  **Class Etiologic agent**  **illness* (n = 126)** **system §**  **Deficiency ¶**  **source Setting** 
Louisiana WNID May 2002 III Pseudomonas aeruginosa** Skin 27 Not applicable 12 Unknown Factory Minnesota DW Jun 1979 IV Detergent AGI 2 Unknown 11D Unknown Golf course Tennessee DW Oct 1988 III Unidentified AGI 89 Ncom 3 Creek Restaurant Tennessee DW Sep 1995 III Hepatitis A Hep 8 Ind 2 Well, spring Private residences * Skin: illness, condition, or symptom related to skin; AGI: acute gastrointestinal illness; and Hep: viral hepatitis. **†** Deaths are indicated in parentheses if they occurred. § Ncom: noncommunity. Community and noncommunity water systems are public water systems that have >15 service connections or serve an average

of >25 residents for >60 days/year. A community water system serves year-round residents of a community, subdivision, or mobile home park. A noncommunity water system serves an institution, industry, camp, park, hotel, or business and can be nontransient or transient. Nontransient systems
serve >25 of the same persons for >6 months of the year but not year-round (e.g., factories and schools), whereas transient systems provide water to places in which persons do not remain for long periods of time (e.g., restaurants, highway rest stations, and parks). Individual water systems are small systems not owned or operated by a water utility that have <15 connections or serve <25 persons. ¶ Deficiency classification for drinking water, water not intended for drinking (excluding recreational water), and water of unkn own intent (see Table 2).  Source**  : Hewitt DJ, Weeks DA, Millner GC, Huss RG. Industrial Pseudomonas folliculitis. Am J Ind Med 2006;49:895–9.

**FIGURE 2. Number* of waterborne-disease outbreaks** **associated with drinking water — United States, 2005–2006**

No

. of oubreak s No

. of

s tate s
>4 1
3 1 2 2
1 7 0 39
* n = 20; numbers are dependent on reporting and surveillance activities

in individual states and do not necessarily indicate that more outbreaks occurred in a given state.



### nity water systems, two (40.0%) were associated with untreated ground water, two (40.0%) were associated with a treatmentdeficiency, and one (20.0%) was associated with both a treatment deficiency and a distribution system deficiency. Among the two outbreaks involving individual water systems, both were associated with contaminated, untreated ground water. The one outbreak involving a community water system was associated with both a treatment deficiency and a distribution system deficiency (Table 10).

Water sources. Seven (87.5%) of the eight WBDOs with deficiencies 1–3 were associated with ground water sources involving wells, and one (12.5%) WBDO was associated with surface water derived from a river (Table 9). Among the seven outbreaks related to ground water sources, four (57.1%) were associated with treatment deficiencies, either inadequate or interrupted chlorination as the only treatment provided, and three (42.9%) were associated with consumption of untreated, contaminated ground water, (Tables 9, 11, and 13; Figure 6). The surface water outbreak occurred during a period of heavy rainfall in a noncommunity system that provided inadequate filtration and disinfection. Deficiencies 5A, 6–11: Contamination of Water at Points Not Under the Jurisdiction of a Water Utility or at the Point-of-Use

Twelve WBDOs were given a deficiency classification of 5A or 6–11. Ten (83.3%) of these WBDOs were associated with Legionella spp., one (8.3%) was associated with Giardia , and one (8.3%) was associated with norovirus G1 (Tables 4 and 5).

Water-quality data. Water-quality data indicating a problem with the drinking water were available for 10 (83.3%) of the 12 WBDOs with an NWU/POU deficiency. Legionella spp. were isolated from the implicated water sampled in nine (90.0%) of 10 legionellosis outbreaks. Water testing in the norovirus outbreak detected norovirus in the storage tank(Maryland, 2006). No water was tested in the giardiasis outbreak; the outbreak was confirmed by clinical testing results.

Deficiency 5A: Legionella in drinking water. All 10 of the drinking water-associated legionellosis WBDOs occurred in residential buildings, hotels, or in institutional settings and were related to the multiplication of Legionella spp. in the building plumbing systems. The majority of cases of legionellosis were diagnosed by urinary antigen testing, which is specific for L. pneumophila serogroup 1 (35 ). Deficiencies 6–11. Two WBDOs were associated with deficiencies 6–11. In one outbreak (California, July 2005), per­

### 48 **MMWR September 12, 2008** 



### sons ill with giardiasis had used a water dispenser at a gym. The water dispenser had been removed at the time of the public health investigation and could not be tested; however, point-of-use contamination of the dispenser spoutseemed the most likely cause of the outbreak. The second outbreak with a POU deficiency (Maryland, 2006) also had SW TD deficiencies 3 and 4. Deficiency 99A–B: Unknown/ Insufficient Information Concerning Contamination of T ap Water The deficiency involv ed in one (5.0%) of the 20 WBDOs could notbe identified because the cause of contamination was unknown. Persons at a church served by a community water system became ill with cryptosporidiosis (Ohio, 2005). Nocommunitywide outbreak was detected and no waterquality violations were detected, suggesting that the contamination might have occurr ed outside the jurisdiction of the water utility

. Investigators noted antiquated and piecemeal water plumbing and sewage lines. However, because it was unclear that this outbreak was caused by premise plumbing contamination, this WBDO is not included in the analysis of the SWTD or NWU/POU deficiencies.



## Waterborne Disease and Outbreaks Associated with Water Not Intended for Drinking and Water of Unknown Intent

Eight WBDOs were associated with either WNID (n = six) or WUI (n = two) (Table 6). The eight WNID/WUI outbreaks caused illness among at least 96 persons and resulted in seven deaths. All deaths were associated with legionellosis. Five (62.5%) WNID/WUI outbreaks involved ARI, and three (37.5%) involved AGI. One (12.5%) of the eight WNID/WUIoutbreaks was categorized as a strength of evidence Class I ranking, two (25.0%) were ranked as Class II, three (37.5%) were ranked as Class III, and two (25.0%) were ranked as Class IV. Etiologic Agents

Five (62.5%) of the eight WNID/WUI outbreaks were attributed to L. pneumophila serogroup 1; these five outbreaks affected 73 persons and resulted in seven deaths. Two of the WNID/WUI outbreaks were attributed to Giardia intestinalis and one outbreak was attributed to E. coli O157:H7 (Table 6). **FIGURE 3. Number of waterborne-disease outbreaks associated with drinking water** **(n = 814),* by year and etiologic agent — United States, 1971–2006**

60

50

40

30

20

10

0
1971 1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 2004 Year Mixed agents † Legionella spp. §

Unidentified Chemical Viral Bacterial Parasitic

* Single cases of disease related to drinking water (n = 16) have been removed from this figure;

therefore, it is not comparable to figures in previous Surveillance Summaries

. † Beginning in 2003, mixed agents of more than one etiologic agent type were included in the

surveillance system. However, the first observation is a previously unreported outbreak in 2002. § Beginning in 2001, Legionnaires’ disease was added to the surveillance system, and Legionella

species were classified separately in this figure.

**FIGURE 4. Number* of waterborne-disease outbreaks** **associated with drinking water, by etiologic agent and month — United States, 2005–2006** 

10

Legionella spp. 8 Infectious (other than Legionella spp.) Unidentified †

6

4

2

0

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

* n = 20. † Unidentified etiology includes suspected etiologies not confirmed during

the outbreak investigation.



### Deficiencies 5B, 5C, 12, and 99D

Each of the eight WNID/WUI outbreaks had one known deficiency: five (62.5%) involved Legionellaspp. in the water system (deficiencies 5B and 5C), two (25.0%) involved WNID unrelated to Legionella(deficiency 12), and one (12.5%) involved WUI (deficiency 99D). Four (80.0%) of the five legionellosis outbreaks involved WNID (deficiency 5B). In three of these outbreaks, the aerosolized water from cooling towers was tested and identified as the source of Legionella

### 49 **Vol. 57 / SS-9 Surveillance Summaries** 

**FIGURE 5. Percentage of waterborne-disease outbreaks (WBDOs) associated with drinking water,**  **by illness and etiology — United States, 2005–2006**

All illness (n = 20)* AGI only (n = nine)*

Mixed agents** 11.1% Acute Bacteria ¶ † AGI 22.2% 45.0% respiratory

50.0%

Viruses 22.2% Hep 5.0% § Unidentified 22.2%

Parasites

22.2%

* AGI: acute gastrointestinal illness; ARI: acute respiratory illness; Hep: viral hepatitis. † All acute respiratory illness was attributed to Legionella spp. § Norovirus suspected based upon incubation period, symptoms, and duration of illness. ¶ Including one outbreak that involved multiple bacterial agents. ** One outbreak that involved bacterial and viral agents.



### spp. In the fourth outbreak, epidemiologic and environmental testing implicated a decorative fountain in a restaurant (36 ). One legionellosis outbreak (20.0%) involved WUI (deficiency 5C). In this outbreak (Pennsylvania, July 2005), environmental water testing failed to determine the source of Legionella spp. Among the three (37.5%) outbreaks unrelated to Legionella

, two involved G. intestinalis , and one was caused by E. coli O157:H7. In the first giardiasis outbreak (California, July 2005), household members became ill while using canal water that had been piped into their home for washing and bathing. Inthe second giardiasis outbreak (Colorado 2006), hikers became ill afterdrinking water from a stream. The outbreak investigation revealed a greaterrisk for becoming ill among those hikers who were less rigorous in their water-treatment practices (i.e., boiling, filtering, or use of chemicals). One outbreak at a sports camp involving 14 persons was caused by E. coli O157:H7(Tennessee 2005). Whereas the environmental investigation did not identify this organism in the water, nonpotable water contaminated with coliforms was leaking onto the pool deck and the tennis courts (Table 6).


## Previously Unreported Outbreaks

Reports of four previously unreported WBDOs associated with drinking water and WNID that occurred during 1979– 2002 were received for this surveillance period (Table 7).

**TABLE 8. Number of waterborne-disease outbreaks (WBDOs) associated with drinking water (n = eight),* by etiologic agent and** **type of water system — United States, 2005–2006 Type of water system**  **†**

**Total Community**  **Noncommunity Individual §**  **Mixed system Etiologic agent**  **WBDOs Cases WBDOs Cases WBDOs Cases**  **WBDOs Cases WBDOs Cases** 

**Bacteria** Campylobacter spp. Escherichia coli O157 , C. jejuni

, and Escherichia coli O145
**Viruses**

Hepatitis A Norovirus G1 **Mixed agents** ¶

Norovirus G1, C. jejuni, and Norovirus G2 **Unidentified**

Unidentified**
**Total Percentage**  **1** 1 0

**0** 0 0
**0** 0
**0** 0
**1 (12.5)**  **32** 32

0

**0** 0 0
**0** 0
**0** 0
**32 (6.2)**  **1** 0 1

**2** 0 2
**1** 1
**1** 1
**5 (62.5)**  **60** 0 6 0

**196**

0 196
**139** 139 **59** 59
**454 (87.6)**  **0** 0 0

**1** 1 0
**0** 0
**1** 1
**2 (25.0)**  **0** 0 0

**16** 16 0
**0** 0
**16** 16
**32 (6.2)**  **0** 0 0

**0** 0 0
**0** 0
**0** 0
**0 (0.0)**  **0** 0 0

**0** 0 0
**0** 0
**0** 0
**0 (0.0)**  **2 1**  **1**

**3 1**  **2**
**1 1** 
**2 2** 
**8 (100.0)**  **92 32**  **60**

**212**

**16 196** 
**139 139** 

**75 75** 
**518 (100.0)** 
* WBDOs with deficiencies 1

**–** 4 and 13 (i.e., surface water contamination, ground water contamination, water treatment deficiency, distribution system

contamination, and untreated chemical contamination of source water) were used for analysis. † Community and noncommunity water systems are public water systems that have >15 service connections or serve an average of >25 residents for >60

days/year. A community water system serves year-round residents of a community, subdivision, or mobile home park. A noncommunit y water system serves an institution, industry, camp, park, hotel, or business and can be nontransient or transient. Nontransient systems serv e >25 of the same persons for >6 months of the year but not year-round (e.g., factories and schools), whereas transient systems provide water to places i n which persons do not remain for long periods of time (e.g., restaurants, highway rest stations, and parks). Individual water systems are small systems not owned or operated by a water utility that have <15 connections or serve <25 persons. § Excludes commercially bottled water and water not intended for drinking, therefore, not comparable to Surveillance Summaries before 2003

**–** 2004. ¶ Multiple etiologic agent types (bacteria, parasite, virus, and/or chemical/toxin) identified. ** Norovirus suspected based on incubation period, symptoms, and duration of illness.

### 50 **MMWR September 12, 2008** 

**TABLE 9. Number of waterborne-disease outbreaks (WBDOs) associated with drinking water (n = eight),* by etiologic agent and** **water source — United States, 2005–2006**
**Water source**
**Total Ground water**  **Surface water Unknown Mixed source**  **Etiologic agent WBDOs Cases**  **WBDOs Cases WBDOs Cases WBDOs Cases**  **WBDOs Cases**
**Bacteria** Campylobacter spp. Escherichia coli O157 , C. jejuni and Escherichia coli O145
**Viruses**

Hepatitis A Norovirus G1 **Mixed agent type** †

Norovirus G1, C. jejuni, and Norovirus G2
**Unidentified**

Unidentified §
**Total Percentage**  **1** 1 0

**3** 1 2
**1** 1
**2** 2
**7 (87.5)**  **32** 32

0

**212**

16 196
**139** 139
**75** 75 **458 (88.4)**  **1** 0 1

**0** 0 0
**0** 0
**0** 0
**1 (12.5)**  **60** 0 60

**0** 0 0
**0** 0
**0** 0
**60 (11.6)**  **0** 0 0

**0** 0 0
**0** 0
**0** 0
**0 (0.0)**  **0** 0 0

**0** 0 0
**0** 0
**0** 0
**0 (0.0)**  **0** 0 0

**0** 0 0
**0** 0
**0** 0
**0 (0.0)**  **0** 0 0

**0** 0 0
**0** 0
**0** 0
**0 (0.0)**  **2 1**  **1**

**3 1**  **2**
**1 1** 
**2 2** 
**8 (100.0)**  **92 32**  **60**

**212**

**16 196** 
**139 139** 

**75 75** 
**518 (100.0)**  * WBDOs with deficiencies 1–3 and 13 (i.e., surface water contamination, ground water contamination, water treatment deficiency, and untreated chemical

contamination of source water) were used for analysis. † Multiple etiologic agent types (bacteria, parasite, virus, and/or chemical/toxin) identified. § Norovirus suspected based on incubation period, symptoms, and duration of illness.

**TABLE 10. Number and percentage of waterborne-disease outbreaks (WBDOs) associated with drinking water (n = eight),* by** **type of deficiency (n = 10) †** **and type of water system — United States, 2005–2006 Type of water system**  **§**

**Total Community**  **Noncommunity Individual ¶**  **Mixed system Type of deficiency**  **No. (%) No. (%) No.**  **(%) No. (%)**  **No. (%)**  1: Untreated surface water intended for drinking 0 0.0 0 0.0 0 0.0 0 0.0 **0 0.0**  2: Untreated ground water intended for drinking 0 0.0 2 33.3 2 100.0 0 0.0 **4 40.0**  3: Treatment deficiency 1 50.0 3 50.0 0 0.0 0 0.0 **4 40.0**  4: Distribution system deficiency, including storage 1 50.0 1 16.7 0 0.0 0 0.0 **2 20.0** 
**Total 2**  **100.0 6**  **100.0 2**  **100.0 0**  **0.0 10**  **100.0** * WBDOs with deficiencies 1–4 and 13 (i.e., surface water contamination, ground water contamination, water treatment deficiency, distribution system

contamination, and untreated chemical contamination of source water) were used for analysis. † Certain WBDOs have multiple deficiencies that are tabulated separately. This table reports 10 deficiencies from eight WBDOs. § Community and noncommunity water systems are public water systems that have >15 service connections or serve an average of >25 residents for

>60 days/year. A community water system serves year-round residents of a community, subdivision, or mobile home park. A noncomm unity water system serves an institution, industry, camp, park, hotel, or business and can be nontransient or transient. Nontransient syste ms serve >25 of the same persons for >6 months of the year but not year-round (e.g., factories and schools), whereas transient systems provide water to places in which persons do not remain for long periods (e.g., restaurants, highway rest stations, and parks). Individual water systems are small systems not owned or operated by a water utility that have <15 connections or serve <25 persons. ¶ Excludes commercially bottled water and water not intended for drinking, therefore, not comparable to Surveillance Summaries before 2003–2004.

**TABLE 11. Number and percentage of waterborne-disease outbreaks (WBDOs) associated with drinking water (n = eight),* by** **type of deficiency (n = eight) and source of water — United States, 2005–2006**
**Water source**
**Total Ground water**  **Surface water Unknown Mixed source**  **Type of deficiency No. (%)**  **No. (%) No. (%)**  **No. (%) No.**  **(%)** 1: Untreated surface water intended for drinking 0 0.0 0 0.0 0 0.0 0 0.0 **0 0.0**  2: Untreated ground water intended for drinking 4 57.1 0 0.0 0 0.0 0 0.0 **4 50.0**  3: Treatment deficiency 3 42.9 1 100.0 0 0.0 0 0.0 **4 50.0** 
**Total 7**  **100.0 1**  **100.0 0**  **0.0 0**  **0.0 8**  **100.0**
* WBDOs with deficiencies 1–3 and 13 (i.e., surface water contamination, ground water contamination, water treatment deficiency, and untreated

chemical contamination of source water) were used for analysis.

### 51 **Vol. 57 / SS-9 Surveillance Summaries** 

**TABLE 12. Number and percentage of waterborne-disease outbreaks (WBDOs) associated with drinking water (n = eight),* by** **predominant illness and type of water system — United States, 2005–2006 Type of water system**  **§**

**Total Community**  **Noncommunity Individual ¶**  **Mixed system Predominant illness**  **† WBDOs Cases**  **(%) WBDOs Cases (%) WBDOs Cases**  **(%) WBDOs Cases (%)**  **WBDOs Cases (%)** 
ARI 0 0 (0.0) 0 0 (0.0) 0 0 (0.0) 0 0 (0.0) **0 0 (0.0)**  AGI 1 32 (100.0) 5 454 (100.0) 1 16 (50.0) 0 0 (0.0) **7 502 (96.9)**  Hep 0 0 (0.0) 0 0 (0.0) 1 16 (50.0) 0 0 (0.0) **1 16 (3.1)** 
**Total 1**  **32 (100.0)**  **5 454 (100.0)**  **2 32 (100.0)**  **0 0**  **(0.0) 8**  **518 (100.0)** * WBDOs with deficiencies 1–4 and 13 (i.e., surface water contamination, ground water contamination, water-treatment deficiency, distribution system

contamination, and untreated chemical contamination of source water) were used for analysis. † ARI: acute respiratory illness; AGI: acute gastrointestinal illness; and Hep: viral hepatitis. § Community and noncommunity water systems are public water systems that have >15 service connections or serve an average of >25 residents for

>60 days/year. A community water system serves year-round residents of a community, subdivision, or mobile home park. A noncomm unity water system serves an institution, industry, camp, park, hotel, or business and can be nontransient or transient. Nontransient syste ms serve >25 of the same persons for >6 months of the year but not year-round (e.g., factories and schools), whereas transient systems provide water to places in which persons do not remain for long periods of time (e.g., restaurants, highway rest stations, and parks). Individual water systems are small systems not owned or operated by a water utility that have <15 connections or serve <25 persons. ¶ Excludes commercially bottled water and water not intended for drinking, therefore, not comparable to Surveillance Summaries before 2003–2004.

**TABLE 13. Number and percentage of waterborne-disease outbreaks (WBDOs) associated with drinking water (n = eight),* by** **predominant illness and water source — United States, 2005–2006**
**Water source**
**Total Ground water**  **Surface water Unknown**  **Mixed source Predominant illness**  **† WBDOs Cases**  **(%) WBDOs Cases (%) WBDOs Cases**  **(%) WBDOs Cases (%)**  **WBDOs Cases (%)** 
ARI 0 0 (0.0) 0 0 (0.0) 0 0 (0.0) 0 0 (0.0) 0 0 (0.0) AGI 6 442 (96.5) 1 60 (100.0) 0 0 (0.0) 0 0 (0.0) 7 502 (96.9) Hep 1 16 (3.5) 0 0 (0.0) 0 0 (0.0) 0 0 (0.0) 1 16 (3.1)
**Total 7**  **458 (100.0)**  **1 60 (100.0)**  **0 0**  **(0.0) 0**  **0 (0.0)**  **8 518 (100.0)**  * WBDOs with deficiencies 1–3 and 13 (i.e., surface water contamination, ground water contamination, water treatment deficiency, and untreated chemical

contamination of source water) were used for analysis. † ARI: acute respiratory illness; AGI: acute gastrointestinal illness; and Hep: viral hepatitis.



### An outbreak of gastroenteritis occurred among two patrons at a golf course (Minnesota, 1979). Acute illness occurred within minutes of consuming water from a water cooler located next to the golf course. The water dispenser had become contaminated after a bucket with detergent residues was used to fill the water container.

During September–November 1995, a hepatitis A outbreak involved eight persons in a community (Tennessee, 1995). All ill persons reported consuming untreated drinking waterfrom ground water sources. Water testing revealed fecal contamination in multiple wells from this community.

One outbreak of gastroenteritis (Tennessee, October 1988) involved an unidentified etiologic agent. The outbreak report implicated water and ice served at a restaurant as the cause of gastroenteritis in 89 persons. Filtered and chlorinated stream water was used for drinking water and ice. Three days beforethe onset of illnesses, the sewage system at an upstream campground overflowed, which presumably overwhelmed the restaurant’s water-treatment system.

One outbreak of Pseudomonas folliculitis among 27 persons occurred in an industrial facility (Louisiana, 2002) and was linked with the use of recycled water in the manufacturing process (37). Although this closed water system was chemically treated, substantially high concentrations of P. aeruginosa were detected in multiple water samples at the facility.


## Surveillance Reports Not Classified as Waterborne Disease and Outbreaks

Nine surveillance reports potentially implicating drinking water or WNID were submitted during 2005–2006 but had insufficient epidemiologic and water-quality data to warrant inclusion in this report as WBDOs. For three reports of legionellosis clusters, common-point sources of transmission were not implicated. Three additional outbreak reports described gastroenteritis within minutes of ingesting drinks at restaurants. Apparently, each of these drinking sources had been contaminated with a cleaning product. Because it was unclear whether the water was contaminated before it was mixed into drinks, these outbreaks were classified as foodborne outbreaks. In 2006, members of three families became ill with giardiasis. Subsequent investigations failed to determine whether private wells serving these families were contaminated. An AGI outbreak among rafting company employees was

### 52 **MMWR September 12, 2008** 



### caused by Campylobacter jejuni, and the drinking water system was suspected to be contaminated. However, despite a thorough investigation, other potential locations of exposure could not be ruled out. Finally, four persons became ill with gastroenteritis, and Aeromonas hydrophila was isolated fromone person. Because no evidence of ground water contamination was detected and the role of Aeromonasin causing waterborne disease has not been definitively established, these cases were not included as an outbreak.



# Discussion Drinking water outbreaks reported to WBDOSS provideimportant data concerning the etiology and trends of waterborne disease. Analysis of these data can provide insight into the effectiveness of EPA regulations, public health oversight, treatment methods, and risk factors for nonpublic systemsand water contaminated outside the jurisdiction of public systems. However, because of incomplete detection, investigation, and reporting of these outbreaks and because the level ofsurveillance and reporting activity varies in different localities, these data are limited in representing the actual occurrence of waterborne-disease outbreaks. In addition, WBDOSS only captures single, nonoutbreak cases of waterborne disease caused by a limited number of agents (e.g., Naegleria fowleri and chemicals demonstrated in water); single cases caused byother waterborne agents are not captured. These factors contribute to the WBDOSS underestimating the burden of endemic waterborne disease related to drinking water.

Multiple factors contribute to the ability of state and local public health agencies to recognize, investigate, and report waterborne-disease outbreaks. These agencies must recognize and link cases of illness to a common water source, whichrequires appropriate laboratory, epidemiologic, and environmental capacity to conduct appropriate investigations. Outbreaks often are recognized through either case investigations of laboratory-confirmed notifiable diseases or complaints ofillness from citizens. This process requires ongoing communication and collaboration between the laboratory, epidemiology and environmental sections of public health agencies. Outbreak reporting might increase as waterborne diseasebecomes better recognized, water system deficiencies are identified, and state surveillance activities and laboratory capabilities increase (38–40 ). Consequently, recommendations for improving WBDO investigations **FIGURE 6. Percentage of waterborne-disease outbreaks (WBDOs) associated with drinking water, by etiologic agent, water system, and water source — United States,**  **2005–2006**

§¶ 

### Etiologic agent (n = 20) Water system (n = eight)

Legionella spp. 50.0% ¶ Individual Unidentified Noncommunity 25.0% 10.0% 62.5%

† Bacteria Community 10.0% 12.5% Mixed agents* Parasites 5.0% Viruses 10.0% 15.0%

** 

### Water source (n = eight)

Surface water 12.5%

Ground water 87.5% 

### include enhancing surveillance activities, increasing laboratory support forclinical specimen and water sample testing, and assessing sources of potential bias ( 41–43 ).

The identification of WBDO etiologic agents depends on multiple factors. I nvestigators must r ecognize the WBDO in a timely manner so that appropriate clinical specimens and environmental samples can be collected. S ubsequently , the laboratories involved must hav e the ability to test for the organism, chemical, or toxin in the clinical and water specimens. WBDOSS data suggest that these capabilities ar e impr oving , giv en the reduction in the proportion of reported WBDOs with an unidentified etiology. During 1971–1996, the etiologic agent was unknown in 51% (338/668) of outbreaks; ho w ever, during 1997– 2006, the etiologic agent was unidenti­ * Each WBDO involves more than one etiologic agent. † Other than Legionella spp. § Deficiencies 1–4. See Table 10. ¶ Does not include commercially bottled water, therefore, not comparable to summaries before

2003–2004. ** Deficiencies 1–3. See Table 11. 

### fied in 24% (35/146) of outbreaks(Figure 3). Reasons for improved etiologic attribution might include increased testing for viral agents in clini­

### 53 **Vol. 57 / SS-9 Surveillance Summaries** 



### cal and water specimens and refinement in water sampling and testing methods. In previous years, stool specimens were tested routinely for enteric bacterial pathogens and parasites,but testing for viral agents was rarely conducted. Identification of water contamination (by coliform bacteria that mightindicate fecal contamination) can provide important information to the epidemiologic investigation and should be attempted when the investigation is conducted in a timely matter. However, collection of water samples also depends on local and state statutory requirements and the availability of investigators who know how to collect the samples. Analyses of specific pathogens and indicators of water contaminationdepend upon the availability of certified or approved laboratories. Many laboratories are certified to conduct standardanalyses for fecal indicators and chemicals, but few laboratories have capabilities for identifying waterborne pathogens, and these tests might be expensive. Collecting water samplesfor pathogen identification might require sampling large quantities of water or filtering large volumes of water through special membranes. Methods for concentrating large volumes ofwater for testing are being developed and disseminated to multiple sites in the United States as standard protocols ( 44 ). Reporting and surveillance bias might occur because certain local and state public health agencies have enhanced capacity to investigate outbreaks. In addition, determining whether an increase or decrease in reporting reflects either an actual change in the incidence of outbreaks or reflects a change in the sensitivity of surveillance practices is unknown. For example, in states thatcollaborate with CDC in the Environmental Health Specialist Network’s waterborne-disease project (EHS-NetWater), the funding of waterborne disease coordinators improved waterborne disease surveillance and interagencycommunication, leading to the reporting of previously unreported WBDOs (Table 7) (31). In addition, EHS-Net Water states are also beginning to report more new outbreaks than they have in previous surveillance periods. Increased reporting likely is attributable to better communication, detection, investigation, and reporting and not as a result of more outbreaks occurring.

Another key limitation of the data collected by WBDOSS is that, for the most part, the information pertains only to outbreaks of waterborne illness and not to endemic waterborne illness, including both acute and chronic health effects. The epidemiologic trends and water-quality concerns observed in outbreaks might not necessarily reflect or correspond with trends associatedwith endemic waterborne illness. In response to the Congressional SDWA Amendments of 1996, EPA and CDC completed and reviewed a series of epidemiologic studies andconvened a national workshop in 2005 to assess the magnitude of endemic waterborne AGI associated with consumption of public drinking water. A joint report on the results of these studies is available at http://www.epa.gov/nheerl/articles/ 2006/waterborne_disease.html. The report includes multiple documents that discuss various methods for estimating the annual number of endemic waterborne-AGI cases associated with public drinking water systems in the United States. Two different but overlapping estimates of the number of endemicAGI cases in the United States were derived: 1) 4.3–11.7 million cases ( 45) and 2) 16.4 million cases associated with public drinking water systems (confidence interval: 5.5–32.8) ( 46 ). These estimates, however, only describe a portion of the annual incidence of endemic waterborne-disease cases. To fully

**FIGURE 7. Percentage of waterborne-disease outbreaks (WBDOs) associated with** **drinking water, by deficiency* — United States, 2005–2006**


### All deficiencies (n = 23)*

Unknown 4.3% (1) †

Source water, treatment No water utility

facility, or distribution jurisdiction or at § system (SWTD) point-of-use

43.5% (10) (NWU/POU) ¶ 52.2% (12)



### SWTD NWU/POU Contamination at point-of-use Untreated 16.7%

40.0% ground water Legionella spp. Distribution in drinking

system water system 20.0% 83.3%

Treatment deficiency 40.0%

* A total of 20 WBDOs but 23 deficiencies. † Deficiency 99A. See Table 14. § Deficiencies 1–4. See Table 14. ¶ Deficiencies 5A, 6–11, 99B. See Table 14.

### 54 **MMWR September 12, 2008** 

**TABLE 14. Waterborne-disease outbreaks associated with drinking water (n = 20), by deficiencies (n = 23)* — United States,** **2005–2006 Deficiency**  **No. of deficiencies Contamination of water at/in the water source, treatment facility, or distribution system (SWTD)**  **†** 1: Untreated surface water intended for drinking 2: Untreated ground water intended for drinking 3: Treatment deficiency (e.g. temporary interruption of disinfection, chronically inadequate disinfection, or inadequate, or no filtration) 4: Distribution system deficiency, including storage (e.g. cross-connection, backflow, and contamination of water mains during construction or repair) 13: Current treatment processes not expected to remove a chemical contaminant (e.g., pesticide contamination of groundwater treated with disinfection only) A: Surface water B: Ground water **Contamination of water at points not under the jurisdiction of a water utility or at the point-of-use (NWU/POU)** §
5: Legionella spp. in water system A: Water intended for drinking 6: Plumbing system deficiency after the water meter or property line (e.g. cross-connection, backflow, and corrosion products) 7: Deficiency in building/home-specific water treatment after the water meter or property line 8: Deficiency or contamination of equipment using or distributing water (e.g. drink-mix machines) 9: Contamination during commercial bottling 10: Contamination during shipping, hauling, or storage A: Water intended for drinking – Tap water B: Water intended for drinking – Commercially bottled water 11: Contamination at point-of-use A: Tap B: Hose C: Commercially bottled water D: Container, bottle, or pitcher E: Unknown **Unknown/Insufficient Information** 99: Unknown/Insufficient information A: Water intended for drinking – Tap water B: Water intended for drinking – Commercially bottled water **Total no. of deficiencies*** **10** 0 4 4

2

0 0
**12**

10 0

0 0 0

0 0

0 1 0 1 0
**1**

1 0 **23** * More than one deficiency might have been identified during the investigation of a single waterborne-disease case or outbreak or case. † Contamination of water and deficiencies occurring in the drinking water system at/in the water source, treatment facility, or distribution system of pipes

and storage facilities. For a community water system, the distribution system refers to the pipes and storage infrastructure under the jurisdiction of the water utility before the water meter or property line (if the system is not metered). For noncommunity and nonpublic water systems, the distribution system refers to the pipes and storage infrastructure before entry into a building or house (e.g., in a service line leading to a house or building). § Contamination of drinking water and deficiencies occurring in plumbing and pipes that are not part of the distribution system or at other points outside

the jurisdiction of a water utility as previously defined. For community systems, this means that after the water meter or property line (if the system is not metered) and for noncommunity and nonpublic systems, this means within the building or house (e.g., in the plumbing inside a house or building) during shipping or hauling, during storage other than in the distribution system, and at the point-of-use).



### describe the overall incidence of waterborne disease, estimates 

## WBDOs Associated with Drinking Wateralso need to include the number of cases of waterborne disEtiologic Agents ease other than AGI and the number of cases associated with nonpublic drinking water systems, commercially bottled Since its addition to WBDOSS in 2001, Legionella has been water, recreational water, WNID, and WUI. If these other the single most commonly reported pathogen associated with types and sources of waterborne disease were considered, the drinking water outbreaks. During 2005–2006, a total of 10 estimated number of cases of endemic waterborne disease (50.0%) of the 20 reported drinking water-associated WBDOs would be higher than the existing estimates of 4–33 million involved Legionellaspp, which is the first time that the numannual cases ( 45,46 ). ber of reported WBDOs associated with ARI has surpassed those associated with AGI in any surveillance period. These WBDOs all occurred as a result of Legionella colonization of plumbing and pipes that are not under the jurisdiction of awater utility and are not specifically subject to EPA regulations. As the predominant drinking water-related pathogen

### 55 **Vol. 57 / SS-9 Surveillance Summaries** 



### in WBDOSS, increased attention must be focused on Legionella to understand its biology, ecology, and inactivationin parts of the water system not addressed by federal regulation so that appropriate public health action to prevent further WBDOs can be taken.

During the 2005–2006 surveillance period, two drinking water-associated WBDOs involved only bacteria (excluding Legionella spp.), compared with five during the 2003–2004 and three during the 2001–2002 surveillance periods. The ongoing occurrence of bacterial WBDOs, despite availableand efficacious treatment practices, underscores the continuing need for protection and treatment of drinking water ( 47 ). In addition, one mixed-agent type outbreak occurred during the 2005–2006 surveillance period, which included bacteria ( C. jejuni ) and viruses (norovirus G1 and G2). The occurrence of mixed-agent type and multiple agent outbreaks emphasizes the importance of considering more than one etiologic agent in outbreak investigations, collecting appropriate specimens for each agent type, and requesting appropriate diagnostic testing for each agent type. In addition, this outbreak was associatedwith sewage contamination of a well, underscoring the importance of proper waste management and proper drinking water system and waste water system designs.

Three WBDOs involving only viruses were reported for the 2005–2006 surveillance period. Two involved norovirus G1, and one involved hepatitis A. Based on incubation period,symptoms, and duration of illness, norovirus was also suspected in the two WBDOs where the etiologic agent was unidentified. All of these WBDOs involved contaminated groundwater that was either untreated or improperly treated (inadequate or interrupted chlorination as the only treatment provided). EPA’s GWR is designed to address vulnerable public ground water systems. However, two of these viral outbreaks occurred in individual nonpublic water systems, and the GWR does not apply to these water systems.

Parasites were identified in two WBDOs during the 2005– 2006 surveillance period. The giardiasis outbreak (California,August 2005) was associated with point-of-use contamination. The reason for contamination could not be determined for the Cryptosporidiumoutbreak; however, investigators noted antiquated and piecemeal water plumbing and sewage lines, suggesting that contamination might have entered throughwater plumbing (Ohio, September 2006). No parasitic outbreaks were associated with contaminated surface water in this surveillance period. Both public surface water systems and public ground water systems under the influence of surface water are regulated under SWTR to protect the public against exposure to Giardia and Cryptosporidium , among other pathogens. The last parasitic disease outbreak associated with surface water and reported to CDC occurred in 2002 in Palau in an untreated noncommunity system supplied by a river. Thedramatic decrease in the number of outbreaks caused by parasites (Figure 3) might be attributable to enhanced EPA regulation of surface water sources.

The etiologic agents of two WBDOs could not be identified, although norovirus was suspected. These two outbreaks represent 10.0% of the 20 drinking water-associated WBDOs reported during 2005–2006 (Figure 6). These two WBDOs represent the lowest number and percentage of outbreaks caused by an unknown etiology in any surveillance period since the beginning of the surveillance system in 1971. Thisdecrease might reflect improved diagnostic capabilities of laboratories and better outbreak investigations, resulting in more rapid and more appropriate specimen collection.
Deficiencies 1–4 and 13: Contamination of Water at/in the Water Source, Treatment Facility, or Distribution System

Typically, EPA regulates the community drinking water supplies from the source water up to the water meter (or up to the property line if the distribution system is not metered).This segment of the drinking water supply system is associated with deficiencies 1–4 and 13 (Table 2): 1) consumptionof untreated surface water intended for drinking, 2) consumption of untreated ground water intended for drinking, 3) treatment deficiencies, 4) distribution system deficiencies, and 13) chemical contamination of source water not removed by existing treatment methods. Noncommunity and individualnonpublic systems also might have distribution system deficiencies (i.e., deficiency 4) if problems occur in pipes or storage infrastructure before entry into a building or house. During the 2005–2006 surveillance period, 40.0% of drinking water-related outbreaks (n = 8) and 43.5% of deficiencies (n = 10) involved deficiencies 1–4. A single WBDO can be associated with more than one deficiency. Deficiency 13 wasnot implicated in any outbreak during the 2005–2006 surveillance period.

Source water. Discussions regarding source water type onlyinclude those WBDOs with deficiencies 1–3 because distribution system deficiencies (deficiency 4) are not necessarily dependent upon the source water type. Also excluded fromthe discussion involving source water types are drinking waterassociated WBDOs with unknown or insufficient information (deficiencies 99A) and outbreaks associated with contamination at points not under the jurisdiction of a water utility or at the point-of -use (deficiencies 5A, 6–11, and 99B).

Surface water. Only one (12.5%) of the eight outbreaks with deficiencies 1–3 was associated with consumption of inadequately-treated surface water. In this outbreak (Oregon, 2005), chronically-inadequate chlorination and inadequate

### 56 **MMWR September 12, 2008** 



### filtration of the river water supplying the camp were cited as the underlying reasons for illness among camp attendees. Sincethe early 1990s, the percentage of reported WBDOs associated with inadequately treated surface water has been declining. This decrease is likely attributable to EPA regulations mandating treatment of surface water used by public water systems. However, this outbreak underscores that regulations alone do not prevent outbreaks and that attention to proper water system operation and maintenance is still required.

Ground water. Seven (87.5%) of the eight outbreaks withdeficiencies 1–3 were associated with consumption of contaminated ground water, either from wells or springs. Among these seven outbreaks, four (57.1%) involved consumption of untreated ground water (deficiency 2), and three (42.9%) involved treatment deficiencies associated with contaminatedground water (deficiency 3). These seven ground waterassociated outbreaks indicate that ground water contamination is a continuing problem. Wells and springs must be protected from contamination, even if disinfection is provided,because ground water can become contaminated with pathogens that are not easily disinfected, and source water conditions might overwhelm the disinfection process (e.g., highly turbid water as a result of excessive rain fall).

Five of the seven outbreaks associated with contaminated ground water during the 2005–2006 surveillance period occurred in noncommunity or community water systems that will be subject to EPA’s new GWR. Beginning in 2009, the GWR will apply to all public systems that use ground water as a source of drinking water. Although this new rule has not yet been fully implemented, it will establish a risk-based approach to target ground water systems that are vulnerable to fecal contamination. The risk-targeting approach includes four major components: 1) sanitary surveys, 2) source watermonitoring to test for the presence of indicators of fecal contamination in the ground water source, 3) corrective action, and 4) compliance-monitoring to ensure that the treatment technology installed to treat drinking water reliably achieves at least 99.99% (4-log) inactivation or removal of viruses. Operators of ground water systems that are identified as being at risk for fecal contamination must take corrective action to reduce the potential for illness from exposure to microbial pathogens.

Because EPA regulations do not apply to individual, nonpublic water systems, WBDOs such as the two involving individual ground water systems reported during 2005–2006will not be subject to the GWR, which could potentially prevent such outbreaks. The protections offered by the GWR will not extend to individual ground water systems unless they are regulated by state or local authorities. Approximately 17million persons in the United States rely on private household wells for drinking water each year, and more than 90,000 new wells are drilled annually throughout the United States ( 48). To safeguard the quality of well water, homeowners should seek information on needed protective measures andimplement recommended operation and maintenance guidelines for private well usage. Homeowners may also choose to protect their own health by purchasing appropriately designedpoint-of-use water-treatment devices and by following instructions for their proper operation and maintenance. AlthoughEPA does not regulate individual water systems, EPA recommendations for protecting private wells are available at http://www.epa.gov/safewater/pwells1.html. Additional effortsshould be taken by public health officials to educate well owners, users, drillers, and local and state drinking water personnel to encourage practices that best ensure safe drinking water for private well-users.

Water treatment. During 2005–2006, five drinking waterrelated WBDOs associated with water-treatment deficiencieswere reported; all were associated with inadequate chlorination. One WBDO was associated with a malfunctioning chlorine feeder (Indiana, 2006). Two outbreaks occurred because existing water treatment was overwhelmed. Heavy rain might have overwhelmed a camp surface water-treatment system in one outbreak (Oregon, 2005), and remnants of Hurricane Katrina might have created surface water runoff into a springsupplying drinking water to a restaurant in the other outbreak (Ohio, 2005). In addition, this small restaurant served a tour group that was substantially larger than was typically served, and the chlorination system could not keep up withthe demand for water. The remaining two WBDOs had inadequate chlorination, but the causes were not specified in thereports. All five outbreaks indicate the need for proper equipment maintenance, adequate capacity of treatment systems to provide potable water during occasional periods of high demand, and education of small water system operators and owners concerning the operation, routine monitoring, and capability of treatment systems under various conditions.

Although treatment deficiencies (deficiency 3) made up the greatest proportion (50.0%) of SWTD deficiencies during the 2005–2006 surveillance period, the majority of (80.0%) of these treatment deficiencies were associated with failures to adequately treat contaminated ground water. When these deficiencies are considered with deficiency 2, contaminated ground water becomes the single largest contributing factor to SWTD-related outbreaks, underscoring the need for the GWR previously described.

Distribution system. Distribution system deficiencies make up the smallest proportion of the SWTD deficiencies during this surveillance period. During 2005–2006, two drinking water-related WBDOs involving distribution system deficien­

### 57 **Vol. 57 / SS-9 Surveillance Summaries** 



### cies occurred. Before one outbreak (Indiana, 2006), a new water main was installed without a valid permit. The water main was pressure tested and was left under pressure with nonpotable water, resulting in a cross-contamination hazard. In the second outbreak, backflow prevention devices were absent on water distribution lines to toilet facilities in a camp(Maryland, 2006). Drinking water quality within the distribution systems of public water supplies is regulated under EPA’sTCR, which is currently undergoing revisions to better protect public health.

Water systems. Discussions regarding water system types (i.e., community, noncommunity, and individual) include drinking water-associated WBDOs with deficiencies 1–4 and 13. Deficiencies in the distribution system are included in these discussions because distribution system problems might be dependent on the type of water system involved. Among the eight drinking water-associated WBDOs with a deficiencyof 1–4, a total of five (62.5%) were associated with noncommunity water systems, two (25.0%) with individual water systems, and one (12.5%) with a community water system. Theproportion (12.5%) of drinking water-related WBDOs associated with community water systems represents the lowest proportion of outbreaks that occurred during the last four surveillance periods (i.e., 1999–2000, 2001–2002, 2003–2004, and 2005–2006). This decrease might reflect the success of federal drinking water regulations protecting water quality in public supplies.

Environmental investigation. To better understand the antecedent events resulting in drinking water-associatedWBDOs, particularly deficiencies 1–4, a new outbreak investigation tool is being developed by EHS-Net, a collaborativeforum of environmental health specialists. These environmental health specialists collaborate with epidemiologists andlaboratorians to identify, investigate, and prevent environmental factors contributing to foodborne and waterborne illnessand disease outbreaks. In 2000, EHS-Net Food was established with funds from CDC’s National Center for Environmental Health, Environmental Health Services Branch, and the FDA and has nine participating state sites that focus on the prevention of foodborne disease. In 2005, EHS-Net Water was piloted with CDC and EPA funds, which support one staff member in each of five states (California, Georgia, Minnesota, New York, and Tennessee) to focus specifically on waterborne-disease investigations. The environmental outbreak investigation tool developed by EHS-Net Water assists with outbreak investigations both by capturing environmental datathat are not collected routinely (e.g., assessment of water system operations) and by clarifying the environmental events and situations (e.g., recent precipitation events) that contributed to WBDOs in small ground water systems. This information will assist public health officials and water system operators and owners in addressing the potential sources of contamination that resulted in an outbreak of waterborne disease.
Deficiencies 5A and 6–11: Contamination of Water at Points Not Under the Jurisdiction of a Water Utility or at the Point-of-Use

A distinction can be made between deficiencies that occur at points NWU/POU and SWTD. During the 2005–2006 surveillance period, more WBDOs were associated with NWU/POU (12 [52.2%]) than with SWTD (10 [43.5%]) (Figure 7). Similar proportions were noted in the 2003–2004 surveillance period, which was the first time the distinction was made between NWU/POU and SWTD deficiencies.

Deficiency 5A. Legionella in water intended for drinking. Legionellosis includes two clinically distinct syndromes:Legionnaires’ Disease (LD), characterized by severe pneumonia, and Pontiac Fever (PF), a febrile, cough illness that does not progress to pneumonia. Legionellosis outbreaks accounted for 50% of all drinking water-associated WBDOs reportedduring 2005–2006 and 83.3% of all NWU/POU deficiencies, indicating that Legionella is a serious public health threat.When outbreaks of legionellosis occur in the setting of contaminated drinking water, they typically manifest as cases of LD rather than PF. Approximately 8,000–18,000 cases of LD occur each year in the United States ( 49 ). Regardless of the syndrome, the source of legionellosis outbreaks typically sharecommon features (e.g., warm stagnant water, inadequate biocide concentrations, and aerosolization, which provides the mechanism for inhalation).

The outbreaks of legionellosis highlight the challenges related to its detection and prevention. LD is underdiagnosed because the majority of patients with community-acquiredpneumonia are treated empirically with broad-spectrum antibiotics ( 50 ). However, because Legionellaspp. are not transmitted from person-to-person and are always acquired from an environmental source, even a single case of LD implies the presence of a contaminated aquatic source to which others can be exposed. Certain host factors (e.g., underlying lung disease and immunodeficiencies) influence the development and severity of legionellosis. Typically, the attack rate during documented LD outbreaks is quite low (i.e., <5%). Not everyone who is exposed in a Legionella -contaminated building is susceptible to symptomatic illness. Identification of two or more cases of LD in association with a potential source is adequate justification for an investigation. All of the legionellosis outbreaks described in this report involved ten or fewer cases. Nonetheless, in all instances except for one, the epidemiologic and laboratory data were compelling enough to implicate point sources that were subsequently remediated.

### 58 **MMWR September 12, 2008** 



### During 2005–2006, a total of eight (80%) of 10 legionellosisoutbreaks associated with drinking water occurred in healthcare settings, demonstrating the propensity for Legionella spp. to colonize potable water systems and underscoring the importance of maintaining a high index of suspicion for legionellosis in health-care settings. Seven outbreaks occurred in acute-care hospitals and one in a long-term–care facility. Legionella spp. colonize the biofilm layer frequently found inside the large, complex plumbing systems of hospitals ( 51 ). This biofilm protects Legionella from biocides and allows the bacteria to amplify to levels sufficient to be transmitted and/or cause disease. Patients in hospitals or long-term–care facilities typically are older and have underlying illness factors thatincrease the risk for disease (e.g., chronic lung disease, diabetes, and immunocompromising conditions).

An outbreak of legionellosis in a health-care setting shouldprompt both an epidemiologic and environmental investigation. Additional cases might point to water exposures that contributed to the outbreak. Environmental sampling of the potable water system and other aerosolized water exposures (e.g., cooling towers) can confirm the source of the outbreak and lead to targeted interventions that prevent additional cases.Superheating and superchlorination are the traditional methods for remediation; however, Legionella might regrow in the distribution system ( 52). Other remediation options are under investigation. Monochloramine might be an effective biocide for Legionellacontrol; hospitals supplied with drinking water containing monochloramine were less likely to have a reported outbreak of LD than those that used water with free chlorine as a residual disinfectant (53). Each health-care facility should develop a plan for legionellosis prevention to address predisposing conditions for Legionella growth in the potable water supply. Guidelines for reducing the risk for legionellosis associated with building water systems are available ( 52).

Deficiencies 6–11. Deficiencies involving drinking waterthat occur at points not under the jurisdiction of a water utility or at the point-of-use have been presented (Table 2). During the 2005–2006 surveillance period, only two reported

non- Legionella WBDOs involving deficiencies in this categorywere reported. Both WBDOs involved point-of-use contamination. One outbreak of giardiasis was associated with contamination of a 5-gallon drinking water ceramic crock dispenser at a gym (California, August 2005). Epidemiologic evidence linked all the cases to the dispenser, although the mechanism of contamination of the dispenser could not be determined. The dispenser had a hand-manipulated spigot and the water was typically replenished once a day, although the dispenser was not regularly cleaned during the suspectedperiod of exposure. Investigators thought that either the employee who replenished the water (she was asymptomatic but her boyfriend was a laboratory-confirmed case) or an ill gym patron who used the spigot might have contaminated the water. An outbreak of norovirus G1 at a camp (Maryland 2006) involved water-treatment and distribution-system deficiencies in addition to contamination at the point-of-use. Garden hoses stored improperly on the ground were used to fill large water containers from which campers filled their cups and water bottles. These point-of-use contamination events illustrate the vulnerability of shared water containers and the importance of practicing good hygiene.



## Waterborne Disease and Outbreaks Associated with Water Not Intended for Drinking and Water of Unknown Intent

During the 2005–2006 surveillance period, eight WBDOs occurred that were associated with WNID or WUI. Five of these outbreaks were associated with Legionella spp. Three of these outbreaks were in health-care settings and attributed to cooling towers. Although the building potable water systemis more frequently implicated in health-care–associated outbreaks, community sources should also be considered. Aerosols containing Legionellacan travel great distances; an investigation of an outbreak among residents of a long-term care facility implicated a cooling tower that was 0.4 km from the facility ( 54 ).Legionellosis clusters might signal a wider community outbreak and should prompt an investigation. In addition,legionellosis outbreaks also can occur in the general population outside the health-care setting, as demonstrated by a community outbreak in South Dakota in 2005. The epidemiologic investigation revealed that a restaurant was the commonexposure among cases. Targeted environmental testing ultimately confirmed the source as the decorative fountain inside the restaurant (36 ). The source of contaminated water could not be identified for the fifth legionellosis outbreak.

The other three non- Legionella WNID/WUI outbreaks were associated with bacterial and parasitic diseases. An outbreak caused by E. coliO157:H7 occurred at a sports camp (Tennessee 2005). The primary water exposure associated with illness could not be identified. Illness was associated with swimming in one of the outdoor pools, dining at pool picnictables, and attending a tennis camp. Unlabeled irrigation faucets drawing water from a nonpotable well were located at multiple points around the tennis courts. Sampling of this water system detected fecal contamination. The remaining two WBDOs involved cases of giardiasis that developed after exposure to WNID. One outbreak involved a family who had canal water piped into their home to use for bathing, dish

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### washing, house cleaning, and laundry (California, July 2005). The second outbreak involved a school trip to a state forest(Colorado 2006). Six of 26 campers became ill. The epidemiologic data indicated that inadequate treatment of river water before consumption was a risk factor. Adding a sports drink powder to river water while concurrently adding iodine for disinfection was a statistically-significant risk factor for becoming ill. The relative risk for boiling water <3 minutes could not be defined because none of the persons who boiled water longer became ill. Both of these giardiasis outbreaks illustrate the risks associated with consuming untreated surface water, even water that might appear pristine.

Backcountry travel (i.e., travel in wilderness environments) in the United States is an increasingly popular activity. In 2004, approximately 12% of Americans aged > 16 years (approximately 26 million persons) went backpacking for one or more nights in backcountry areas during the previous 12 months ( 55). Limited information is available concerning the risk factors for illness in the backcountry and about the health outcomes of visitors who use parks in backcountry areas. Several studies indicate that as many as 3.8%–56% of long-distancehikers and backpackers experience gastrointestinal illness during their time in the backcountry ( 56–61 ). Given the increasing popularity of backcountry use, this burden of illness could have significant medical and economic implications. Althoughthe advice to universally filter and disinfect backcountry drinking water to prevent disease has been debated ( 62), the health consequences of ignoring that standard water treatment advice have been documented in WBDOSS, although they have not been well-defined through research studies.


## Previously Unreported Outbreaks

This report discusses information concerning four previously unreported WBDOs. Two of these outbreaks occurred in Tennessee, one in Minnesota, and one in Louisiana. TheTennessee and Minnesota state health departments are partners in EHS-Net Water. Initial surveys by three of the five participating EHS-Net Water states have revealed at least 75 outbreaks or health events previously unreported to CDC, including the three drinking water outbreaks reported in this Surveillance summary, nine drinking water outbreaks from New York State included in the previous Surveillance Summary ( 5 ), and 63 recreational water-related outbreaks or health events reported in the recreational water Surveillance Summary (30 ). In addition to reporting historical outbreaks, these states areworking to improve the sensitivity of their current waterbornedisease outbreak detection. Additional EHS-Net Water projects are underway to improve the practice of environmental healthservice programs; translate the findings into improved prevention efforts; offer training opportunities to current and future environmental health specialists; and strengthen thecollaboration among epidemiology, laboratory, and environmental health programs. The EHS-Net Water activities indicate that increased effort and resources, specifically directed at waterborne-disease reporting, could result in the identification of previously unreported historical outbreaks. As EHS-Net Water refines the process for identifying and investigating current waterborne-disease incidents, these efforts might result in enhanced reporting of waterborne outbreaks from these and other states.



# Conclusion Data collected as part of the national WBDOSS are used to describe the epidemiology of waterborne-disease outbreaks inthe United States. Trends regarding water systems and deficiencies implicated in these WBDOs are used to assess whether regulations for water treatment and water-quality monitoring are adequate to protect public health. Trends regarding the etiologic agents responsible for these outbreaks are used toassess the need for different interventions and changes in policies and resource allocations.

Two primary trends can be observed from the 2005–2006 surveillance period data. Since it was first included in WBDOSS in 2001, Legionella has become the single most common cause of reported outbreaks in WBDOSS. This does not mean that Legionella is a more important cause of waterborne disease than other agents (e.g. norovirus) nor does it mean than legionellosis outbreaks are increasing because theyhave only been included in the WBDOSS since 2001. Therefore, there is a limited basis for historical comparison. However, outbreaks associated with other agents are not being reported as frequently as outbreaks caused by Legionella

. Whether this is a result of barriers to laboratory confirmation of non- Legionella pathogens in clinical specimens and environmental samples, lack of detection of non- Legionella pathogens as a result of different incubation periods or milder illness, use of adequate water-treatment technologies for non- Legionella pathogens, or other factors that might be responsible for fewer outbreaks associated with non- Legionella is not clear.The second major trend observed in the 2005–2006 surveillance period is the high proportion of WBDOs associated with contaminated ground water, whether consumed untreated or with inadequate treatment. Until the GWR was finalized in 2006, federal drinking water regulations have concentrated on protecting consumers from contaminated surface water. These rules probably have contributed to the decrease in the number and proportion of reported WBDOs associated with contaminated surface water that have been observed during

### 60 **MMWR September 12, 2008** 



### the previous twenty years. Similar protections against the consumption of contaminated ground water were absent until the development of the GWR, which was finalized in 2006. This rule, which is expected to be enacted in 2009, might result in a similar decline in the number of ground water– associated WBDOs.

Surveillance for waterborne agents and WBDOs occurs primarily at the local and state levels (including territories and FAS). Public health authorities at these levels are responsible for detecting and recognizing drinking water-associatedWBDOs and implementing appropriate prevention and control measures (Box). Improved communication among local and state public health departments, regulatory agencies, and

water utilities will aid in the detection and control of WBDOs. Routine reporting or sharing of water-quality data within the health and environmental health departments is recommended. Other means of improving surveillance at the local, state, andfederal levels include additional review and follow up of information gathered through other mechanisms (e.g., issuances of boil-water advisories or reports of illness associated with agents thought to be waterborne).

A number of efforts have been initiated at the local, state, and national levels to improve the detetection, investigation, and reporting of WBDOs. CSTE passed a position statement at the 2006 annual meeting making WBDOs, as a unit ofreporting, nationally notifiable and reportable to CDC starting in 2007. Adoption of this CSTE recommendation at the state level through state-specific legislative action might improve reporting of WBDOs at the state and local levels.

In addition, to improve timeliness and completeness of reporting, CDC and EPA are collaborating with public health jurisdictions to implement electronic reporting of WBDOs

**BOX. Organizations that provide assistance in investigations of waterborne disease and outbreaks (WBDOs)** 

### State and territorial health departments can request Telephone: 404-639-2215 epidemiologic assistance and laboratory testing from Internet: http://www.cdc.gov/legionella CDC to investigate WBDOs. CDC and the U.S. Envi­ • Testing for Parasites ronmental Protection Agency (EPA) can be consulted Division of Parasitic Diseases regarding engineering and environmental aspects of National Center for Zoonotic, Vector-Borne, and drinking water treatment during and after outbreaks and Enteric Diseases collection of large-volume water samples to identify Coordinating Center for Infectious Diseases, CDC pathogens that require special protocols for their recov- Telephone: 770-488-7775ery. EPA and the U.S. Geological Survey can be consulted for assistance with hydrogeologic investigations • Testing for Viruses of outbreaks where untreated ground water is suspected. Division of Viral Diseases National Center for Immunization and Respiratory • Environmental Protection Agency Safe Drinking Diseases

Water Hotline Coordinating Center for Infectious Diseases, CDC Telephone: 800-426-4791 Telephone: 404-639-3607 E-mail: hotline-sdwa@epa.gov Internet: http://www.epa.gov/safewater • State Reporting of Waterborne Disease and Outbreaks • Testing for Bacterial Enteric Organisms Division of Parasitic Diseases

Division of Foodborne, Bacterial, and Mycotic National Center for Zoonotic, Vector-Borne, and

Diseases Enteric Diseases National Center for Zoonotic, Vector-Borne, and Coordinating Center for Infectious Diseases, CDC

Enteric Diseases Telephone: 770-488-7775 Coordinating Center for Infectious Diseases, CDC Fax: 770-488-7761 Telephone: 404-639-1798 Note: All WBDOs at the local level should be reported to the state health department. • Request for Information on Testing for Legionella

Division of Bacterial Diseases • CDC Reporting Form CDC 52.12 (rev.01/2003) National Center for Immunization and Respiratory Internet: http://www.cdc.gov/healthyswimming/

Diseases downloads/cdc_5212_waterborne.pdf Coordinating Center for Infectious Diseases, CDC

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### through the National Outbreak Reporting System (NORS).NORS is a more systematic data-collection tool and will provide public health agencies and waterborne-disease researchers with the evidence base they need to identify the causes ofWBDOs and understand the environmental factors contributing to these outbreaks.

EHS-Net Water, a collaborative project between EPA, CDC, and five state health departments, is an effort to improve WBDO identification, investigation, response, and reporting. EHS-Net Water sites initially focused on understanding theirstate-specific surveillance systems, which resulted in the identification and reporting of numerous previously unreported historical outbreaks to WBDOSS. Subsequent efforts are focusing on improving the environmental investigation of drinking water outbreaks, particularly in small groundwater systems.

In May 2007, EPA and CDC convened a workshop toaddress improving the recognition, investigation, and reporting of waterborne-disease outbreaks. Participants includedepidemiologists, environmental engineers, scientists, environmental health specialists, other public health professionals, and water-industry professionals from 44 states, the District of Columbia, and Puerto Rico. Workshop recommendations included 1) improving the communication and coordination between agencies investigating waterborne-disease outbreaks; 2) conducting training for outbreak investigators, laboratory analysts, and water system operators; 3) focusing efforts onoutbreak prevention; 4) enhancing surveillance; 5) strengthening outbreak investigations; and 6) improving outbreak reporting.

Efforts to enhance awareness, training, resources, and communication will improve the quality of the data in WBDOSS. These efforts should make public health activities related to waterborne disease more efficient and reduce the burden of WBDOs.

References

1. Gorman AE, Wolman A. Water-borne outbreaks in the United States

and Canada and their significance. J Amer Water Works Assoc 1939; 31:225–75. 2. Eliassen R, Cummings RH. Analysis of waterborne outbreaks, 1938­

45. J Amer Water Works Assoc 1948;40:509–28. 3. Weibel SR, Dixon FR, Weidner RB, McCabe LJ. Waterborne disease

outbreaks 1946–60. J Amer Water Works Assoc 1964;56:947–58. 4. Craun GF, McCabe, LJ. Review of the causes of waterborne-disease

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Water Works Association 1997;89:18–36. 9. Environmental Protection Agency. Drinking water; national primary

drinking water regulations; total coliforms (including fecal coliforms and E. coli ); final rule. 40 CFR Parts 141 and 142. Federal Register 1989;54:27544–68. 10. Environmental Protection Agency. Drinking water; national primary drinking water regulations; total coliforms; corrections and technical amendments; final rule. 40 CFR Parts 141 and 142. Federal Register 1990;55:25064–5. 11. Environmental Protection Agency. National primary drinking water regulations: ground water rule; proposed rules. 40 CFR Parts 141 and 141. Federal Register 2000;65:30194–274. 12. Environmental Protection Agency. National primary drinking water regulations: ground water rule. 40 CFR Parts 141 and 141. Federal Register 2006;71:65573–660. 13. Environmental Protection Agency. Drinking water; national primary drinking water regulations; filtration, disinfection; turbidity, Giardia lamblia , viruses, Legionella , and heterotrophic bacteria; final rule. 40 CFR Parts 141 and 142. Federal Register 1989;54:27486–541. 14. Environmental Protection Agency. National primary drinking water regulations: interim enhanced surface water treatment; final rule. 40 CFR Parts 9, 141, and 142. Federal Register 1998;63:69478–521. 15. Environmental Protection Agency. National primary drinking water regulations: long term 1 enhanced surface water treatment rule; final rule. 40 CFR Parts 9, 141, and 142. Federal Register 2002;67:1812–44. 16. Environmental Protection Agency. National primary drinking waterregulations: monitoring requirements for public drinking water supplies: Cryptosporidium

, Giardia , viruses, disinfection byproducts, water treatment plant data and other information requirements; final rule. 40 CFR Part 141. Federal Register 1996;61:24353–88. 17. Environmental Protection Agency. National primary drinking water regulations: stage 2 disinfectants and disinfection byproducts rule. 40 CFR Parts 9, 141, and 142. Federal Register 2006;71:387–493. 18. Environmental Protection Agency. National primary drinking water regulations: long term 2 enhanced surface water treatment rule. 40 CFR Parts 9, 141 and 142. Federal Register 2006;71:653–702. 19. Environmental Protection Agency. National primary drinking water regulations: filter backwash recycling rule; final rule. 40 CFR Parts 9, 141, and 142. Federal Register 2001;66:31086–105. 20. Environmental Protection Agency. National primary drinking water regulations; arsenic and clarifications to compliance and new source contaminants monitoring. 40 CFR Parts 9, 141, and 142. Federal Register 2001;66:6976–7066. 21. Environmental Protection Agency. National primary drinking water regulations for lead and copper; final rule. 40 CFR Parts 9, 141, and 142. Federal Register 2000;65:1949–2015. 22. Environmental Protection Agency. Announcement of the drinking water contaminant candidate list; notice. Federal Register 1998;63: 10274–87. 23. Environmental Protection Agency. Drinking water contaminant candidate list 2; final notice. Federal Register 2005;70:9071–7.

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24. Environmental Protection Agency. Unregulated contaminant monitoring regulation for public water systems; analytical method for list 2contaminants; clarifications to the unregulated contaminant monitoring regulation. 40 CFR Part 141. Federal Register 2001;66:2273–308.25. Environmental Protection Agency. Unregulated contaminant monitoring regulation for public water systems; amendment to the list 2 rule and partial delay of reporting of monitoring results. 40 CFR Part 141. Federal Register 2001;66:46221–4.26. Environmental Protection Agency. Unregulated contaminant monitoring regulation for public water systems; establishment of reporting date. 40 CFR Part 141. Federal Register 2002;67:11043–6.27. Environmental Protection Agency. Unregulated contaminant monitoring regulation: approval of analytical method for Aeromonas ; national primary and secondary drinking water regulations: approval of analytical methods for chemical and microbiological contaminants. 40 CFR Part 141. Federal Register 2002;67:65888–902. 28. Lee SH, Levy DA, Craun GF, Beach MJ, Calderon RL. Surveillance for waterborne-disease outbreaks—United States, 1999–2000. In: Surveillance Summaries, November 22, 2002. MMWR 2002;51 (No. SS-8):1–47. 29. Environmental Protection Agency. Establishment of the total coliform rule distribution system advisory committee. 40 CFR Part 141. Federal Register 2007;72:35869–70.30. Yoder JS, Hlavsa M, Craun GF, et. al. Surveillance for waterborne disease and outbreaks associated with recreational water use and other aquatic facility-associated health events — United States, 2005–2006. In: Surveillance Summaries, September 12, 2008. MMWR 2008;57 (No. SS-9):39–70. 31. CDC. Summary of notifiable diseases—United States, 2006. MMWR 2008;55. 32. Environmental Protection Agency. Factoids: drinking water and ground water statistics for 2007. March 2008, April 2008. Available at http://www.epa.gov/safewater/data/getdata.html.33. Environmental Protection Agency. Private drinking water wells. February 21, 2006. Available at http://www.epa.gov/safewater/privatewells/ index2.html. 34. CDC. Gastroenteritis among attendees at a summer camp—Wyoming, June–July 2006. MMWR 2007;56:368-370. 35. Benin AL, Benson RF, Besser RE. Trends in Legionnaires’ disease, 1980– 1998: declining mortality and new patterns of diagnosis. Clin Infect Dis 2002;35:1039–46. 36. O’Loughlin RE, Kightlinger L, Werpy MC, et al. Restaurant outbreak of Legionnaires’ disease associated with a decorative fountain: an environmental and case control study. BMC Infect Dis. 2007; 7:93. 37. Hewitt DJ, Weeks DA, Millner GC, Huss RG. Industrial Pseudomonas folliculitis . Amer J Ind Med 2006;49:895–9. 38. Frost FJ, Calderon RL, Craun GF. Waterborne disease surveillance: findings of a survey of state and territorial epidemiology programs. J Environ Health 1995;58:6–11. 39. Frost FJ, Craun GF, Calderon RL. Waterborne disease surveillance. J Amer Water Works Association 1996;88:66–75. 40. Hopkins RS, Shillam P, Gaspard B, Eisnach L, Karlin RJ. Waterborne disease in Colorado: three years’ surveillance and 18 outbreaks. Am J Public Health 1985;75:254–7. 41. Craun GF, Frost FJ, Calderon RL, et al. Improving waterborne disease outbreak investigations. Int J Environ Health Res 2001;11:229–43.42. Frost FJ, Calderon RL, Craun GF. Improving waterborne disease surveillance. In: Pontius FW, ed. Drinking water regulation and health. New York, NY: John Wiley & Sons; 2s003:25–44. 43. Hunter PR, Waite M, Ronchi E, eds. Drinking water and infectious disease: establishing the links. Boca Raton, FL: CRC Press; 2003:221. 44. Hill VR, Kahler AM, Jothikumar N, Johnson TB, Hahn D, Cromeans TL. Multistate evaluation of an ultrafiltration-based procedure for simultaneous recovery of enteric microbes in 100-liter tap water samples. App Environ Microbiol 2007;73:4218–25. 45. Colford JM, Roy SL, Beach MJ, Hightower A, Shaw SE, Wade TJ. A review of household drinking water intervention trials and an approach to the estimation of endemic waterborne gastroenteritis in the United States. J Water and Health 2006;4(Suppl 2):71–88. 46. Messner M, Shaw S, Regli S, Rotert K, Blank V, Soller J. An approachfor developing a national estimate of waterborne disease due to drinking water and a national estimate model application. J Water Health 2006;4(Suppl 2):201–40. 47. Environmental Protection Agency, Office of Water. The history of drinking water treatment. Available at http://www.epa.gov/safewater/ consumer/pdf/hist.pdf. 48. US General Accounting Office. Drinking water: information on the quality of water found at community water systems and private wells.Washington, DC: US General Accounting Office; 1997. GAO publication no. GAO/RCED-97–123.49. Marston BJ, Plouffe JF, File TM, et al. Incidence of communityacquired pneumonia requiring hospitalization. Results of a populationbased active surveillance study in Ohio. The community-based pneumonia incidence study group. Arch Intern Med 1997;157:1709-18. 50. Bartlett JG. Decline in microbial studies for patients with pulmonary infections. Clin Infect Dis 2004;39:170–2. 51. Fields BS, Benson RF, Besser RE. Legionella and Legionnaires’ disease: 25 years of investigation. Clin Microbiol Rev 2002;15:506–26. 52. SHRAE Standard Project Committee. Minimizing the risk of legionellosis associated with building water systems. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.; 2000. 53. Heffelfinger JD, Kool JL, Fridkin S, et al. Risk of hospital-acquired Legionnaires’ disease in cities using monochloramine versus other water disinfectants. Infect Control Hosp Epidemiol 2003;24:569–4. 54. Phares CR, Russell E, Thigpen MC, et al. Legionnaires’ disease amongresidents of a long-term care facility: The sentinel event in a community outbreak. Am J Infect Control 2007;35:319–3 55. Cordell K, Green G, Betz C, Fly M, Stephens B. Recreation statistics update. Update Report No. 1, August 2004—participation rates for outdoor activities in 2004. Available at: http://www.srs.fs.usda.gov/ trends/RECUPDATES/recupdate0804.pdf. 56. Boulware DR, Forgey WW, Martin WJ. Medical risks of wilderness hiking. Am J Med 2003;114:288–3. 57. Boulware DR. Influence of hygiene on gastrointestinal illness among wilderness backpackers. J Travel Med 2004;11:27–33. 58. Boulware DR. Gender differences among long-distance backpackers:a prospective study of women Appalachian Trail backpackers. Wilderness Environ Med 2004;15:175–80. 59. Twombly SE, Schussman LC. Gender differences in illness and injury rates on wilderness backpacking trips. Wilderness Environ Med 1995;4: 363–76. 60. Gardner TB, Hill DR. Illness and injury among long-distance hikers on the Long Trail, Vermont. Wilderness Environ Med 2002;13:131–4. 61. Crouse BJ, Josephs D. Health care needs of Appalachian trail hikers. J Fam Pract 1993;36:521–5. 62. Welch TR. Evidence-based medicine in the wilderness: The safety of backcountry water. Wilderness Environ Med 2004;15:235–7.

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# Appendix A Glossary of Definitions

action level A specified concentration of a contaminant in water. If this concentration is reached or exceeded, certain actions (e.g., further treatment and monitoring) must be taken to comply with a drinking water regulation.

agent See etiologic agent. aquifer A geologic formation or part of a formation (e.g., gravel, sand, or porous stone) that yields water to wells or springs.

backflow A hydraulic condition caused by a difference in water pressure that causes nonpotable water or other liquid to enter the potable water system by either backpressure or backsiphonage. See cross-connection. backpressure A hydraulic condition that results when pressure from a customer’s water system (e.g., potentially nonpotable water) is higher than pressure in the public water system, resulting in backflow of water into the public water system. backsiphonage A hydraulic condition caused by negative or subatmospheric pressure within a water system, resulting in backflow.

biofilm Microbial cells that adhere to a surface through a matrix of primarily polysaccharide materials in which they are encapsulated. Biofilms can grow on piping and surfaces of watersystems and can be difficult to remove. They offer protection to microbes from disinfectants (e.g., chlorine) in the water. boil-water advisory A statement to the public advising that tap water must be boiled before drinking.

bottled water Commercially produced bottled water.

class A categorization given to waterborne disease and outbreaks (WBDOs) indicating to the strength of the epidemiologic and water-quality data implicating water as the source of the disease or outbreak (see Table 3).

coliforms All aerobic and facultative anaerobic, gram-negative, nonspore-forming, rod-shaped bacteria that ferment lactose with gas formation within 48 hours at 95°F (35°C). Coliforms are mostly harmless bacteria that live in soil and water as well as the gut of humans and animals. community water system A public water system that has at least 15 service connections used by year-round residents or that regularly serves at least 25-year-round residents. The system might be owned by a private or public entity providing water to a community, subdivision, or mobile home park.

cross-connection Any actual or potential connection between a drinking water supply and a possible sourceof contamination or pollution (i.e., nonpotable water). Under this condition, contaminated water might flow back into the drinking water system. See backflow. deficiency An antecedent event or situation contributing to the occurrence of a waterborne disease or outbreak.

dermatitis Inflammation of the skin. In this report, the term dermatitis is used to denote a broad category of skin-related symptoms (e.g., folliculitis, cellulitis, chemical burns, or rash).

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### disinfection A treatment that kills microorganisms (e.g., bacteria, viruses, and protozoa); in water treatment, a chemical (commonly chlorine, chloramine, or ozone) or physical process (e.g., ultraviolet light) may be used.disinfection by-products Chemicals formed in water by the reaction between organic matter and other waste products and disinfectants. distribution system Water pipes, storage reservoirs, tanks, and other means used to deliver drinking water to consumers or to store finished water before delivery to a customer. In community water systems, the distribution system is under the jurisdiction of a water utility and ends at thewater meter or at the customer’s property line (if the system is not metered). In noncommunity and nonpublic individual water systems, the distribution system ends at the point where water enters the building or house. See plumbing. etiologic agent The pathogen, chemical, or toxin causing a waterborne disease or outbreak. Infectious etiologic agents are bacteria, parasites, viruses, or fungi.

fecal coliforms Coliform bacteria that grow and ferment lactose to produce gas at 112.1°F (44.5°C) in <24 hours. These bacteria are associated with human and animal wastes, and their presence in water might be an indication of recent sewage or animal waste contamination.

filtration In water treatment, the process of passing water through one or more permeable membranes or media of small diameter (e.g., sand, anthracite, and diatomaceous earth) toremove suspended particles from the water. Filters might be effective in removing pathogens, depending on the type and operation.

finished water The water (e.g., drinking water) delivered to the distribution system after treatment, if any.

free chlorine The chlorine in water that is not combined with other constituents, therefore, serving as an effective disinfectant (also referred to as free available chlorine and residual chlorine). ground water Water that is contained in interconnected pores in an aquifer. ground water system A system that uses water extracted from an aquifer (i.e., a well or spring) as its source. ground water under the di rect As defined by the U.S. Environmental Protection Agency (EPA), any water beneath the influence of surface water surface of the ground with substantial occurrence of insects or other macrooganisms, algae, or large-diameter pathogens (e.g., Giardia intestinalis or Cryptosporidium ), or substantial and relatively rapid shifts in water characteristics (e.g., turbidity, temperature, conductivity, or pH) that closely correlate with climatologic or surface water conditions. Direct influence must be determined for individual sources in accordance with criteria established by the state. individual water system A water system that does not meet the EPA definition for a public water system. The system might serve a single family or farm not having access to a public water system, or it mightregularly serve as many as 24 persons or 14 connections. States are responsible for regulating these water systems. karst aquifer An aquifer characterized by water-soluble limestone and similar rocks in which fractures or cracks have been widened by the dissolution of the carbonate rocks by ground water; the aquifer might contain sinkholes, tunnels, or even caves.

maximum contaminant level The maximum permissible concentration (i.e., level) of a contaminant in water supplied to any user of a public water system.

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### mixed-agent outbreak More than one type of etiologic agent is identified in clinical specimens from affected persons, and each etiologic agent is found in more than 5% of positive clinical specimens (e.g., an outbreak with Giardia spp. [parasites] and Salmonella spp. [bacteria] with each agent identified in >5% of stool specimens).

mixed-illness outbreak More than one type of illness is reported by more than 50% of patients in a single outbreak (e.g., a combination of gastroenteritis and dermatitis).

mixed-source outbreak More than one type of source water is implicated in the outbreak (e.g., a combination of ground water and surface water). mixed-system outbreak More than one type of water system is implicated in the outbreak (e.g., a combination of noncommunity and individual water systems).noncommunity water system A public water system that is not a community system; it does not serve year-round residents. There are two types: transient and nontransient noncommunity systems. nontransient noncommunity A public water system that is not a community system and that regularly serves at least 25 of water system the same persons for more than 6 months per year but not year-round (e.g., a school, a factory, or a business with its own water supply). plumbing Water pipes, storage reservoirs, tanks, and other means used to deliver drinking water to consumers inside buildings or houses or to store drinking water inside buildings or houses before consumption. In community water systems, the plumbing begins after the water utility’s water meter or at the property line (if the distribution system is not metered). In noncommunity and nonpublic individual water systems, the plumbing begins at the point where water enters the building or house. See distribution system. predominant illness The category of illness reported by at least 50% of ill respondents (e.g., gastroenteritis, dermatitis, or acute respiratory illness). When more than one illness category is reported for a single WBDO, they are listed together as predominant illnesses. These mixed illness WBDOs are analyzed separately from WBDOs with single illnesses.
primary water exposure For use in this report, a classification used for the source of contaminated water not intended for drinking or contaminated water of unknown intent. public water system A system, classified as either a community water system or a noncommunity water system, that provides piped water to the public for human consumption and is regulated under theSafe Drinking Water Act. Such a system must have at least 15 service connections or regularly serve at least 25 persons daily for at least 60 days per year.

raw water Surface water or ground water that has not been treated in any way. reservoir, impoundment An artificially maintained lake, created for the collection and storage of water. This body of water can be available as a source of raw water for drinking purposes and/or recreational use. In certain instances, a finished water storage facility in the distribution system might also be called a reservoir. setting Location where exposure to contaminated water occurred (e.g., restaurant, water park, or hotel).

source water Untreated water (i.e., raw water) used to produce drinking water.

surface water All water on the surface (e.g., lakes, rivers, reservoirs, ponds, and oceans) as distinguished from subsurface or ground water.

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### total coliforms Fecal and nonfecal coliforms that are detected by using a standard test. The extent to which total coliforms are present in water can indicate the general quality of that water and the likelihood that the water is fecally contaminated by animal and/or human sources.
transient noncommunity A public water system that is not a community system and that does not regularly serve at water system least 25 of the same persons for more than 6 months per year. These systems provide water to places where persons do not remain for long periods (e.g., restaurants, campgrounds, highway rest stations, or parks with their own public water systems).

untreated water Surface water or ground water that has not been treated in any way (i.e., raw water). water not intended for drinking Water that has not been treated for human consumption in conformance with EPA drinking water standards and that is provided for uses other than for drinking. This might include water used in occupational settings; lakes, springs, and creeks used as drinking water by campers and boaters; irrigation water; and other nonpotable water sources with or without taps but does not include exposure to recreational water or flood water.

water of unknown intent The information about the water is insufficient to determine for what purpose it is being provided or used and whether is has been treated for human consumption in conformance with EPA drinking water standards.

water system A system for the provision of water for human consumption through pipes or other constructed conduits. This includes any collection, treatment, storage, and distribution facilities used primarily in connection with such a system.

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# Appendix B Descriptions of Selected Waterborne Disease Outbreaks Associated with Drinking Water, Water Not Intended for Drinking, and Water of Unknown Intent

**State in No. of**  **which WBDO cases**  **Date occurred Etiologic agent (deaths)**  **Description of WBDO Bacteria**  February 2006 Indiana Campylobacter spp. 32	 Thirty-two county residents who developed gastrointestinal illness were included in a case-control study that implicated municipal water as the source of infection. Seven of nine people who provided stool specimens tested positive for Campylobacter species; and routine water samples from the treatment facility tested positive for total coliforms and Escherichia coli at the time of the outbreak. The investigation determined that a chlorinator had malfunctioned before the outbreak, resulting in inadequate chlorination of the water supply, and that cross-contamination also might have occurred when a new water main was pressure-tested with non-potable water.

May 2005 Oregon Escherichia coli O157:H7, 60	 Attendees of an outdoor school program at a camp developed C. jejuni, and E. coli O145 gastrointestinal illness with a median duration of four days. Stool samples were collected from 57 cases. Nine persons tested positive for E. coli O157:H7, three persons tested positive for C. jejuni, two persons tested positive for E. coli O145; and three persons tested positive for both E. coli O157:H7 and C. jejuni . The camp was required to upgrade the surface water-treatment system, which was suspected of providing inadequate treatment after heavy rainfall conditions. Raw water tested positive for fecal coliforms and E. coli approximately 1 week after the first case-patient became ill.

May 2005 South Dakota Legionella pneumophila 18 (1) Eighteen confirmed cases of Legionnaires’ disease were reported serogroup 1 over a 5-month period in Rapid City, South Dakota. An investigation, including a case-control study and environmental sampling, wasconducted. A small, decorative fountain lacking obvious aerosolgenerating capacity was implicated. Clinical and environmental L. pneumophila serogroup 1 Benidorm isolates had identical sequence-based typing (SBT) patterns. ( **Source:** O’Loughlin RE, Kightlinger L, Werpy, M, et al. Restaurant outbreak of Legionnaires’ disease associated with a decorative fountain: an environmental and case control study. BMC Infect Dis 2007;7:93).
April 2006 Texas L. pneumophila serogroup 1 10 (3)	 Ten confirmed cases of Legionnaires’ disease, diagnosed by urine antigen and culture, were reported during spring 2005 after exposure to a hospital in San Antonio, Texas. The potable hot water supply of the newly constructed and recently opened inpatient building was determined to be the most likely source of the outbreak. Multiple L. pneumophila serogroup 1 strains were identified from environmental isolates taken from the hospital building; one previously unreported environmental strain matched a case-patient isolate.
May 2002 Louisiana Pseudomonas aeruginosa 27	 Thirty-eight employees at a cardboard box manufacturing facility were surveyed regarding recent dermatologic symptoms. Twenty-seven employees reported rashes that were suspected to be work-related and were consistent with P. aeruginosa infection. The facility had recently switched to a closed-water system. Water used in manufacturing processes and cleaning was treated and re-used as plant process water. Water samples from multiple sites using this water contained high concentrations of P. aeruginosa . Contributing factors noted from the water samples included elevated water temperatures, high organic content, elevated pH levels and varying disinfectant levels. The observation was made that certain areas of the water system were accessed substantially less frequently than others and that the ability of Pseudomonas to produce biofilms in hoses or pipes might have limited the effectiveness of the treatment methods. **(Source:** Hewitt DJ., et al. Industrial Pseudomonas folliculitis. Am J Ind Med 2006; 49:895–9).

### 68 **MMWR September 12, 2008** 

**State in No. of**  **which WBDO cases**  **Date occurred Etiologic agent (deaths)**  **Description of WBDO**
**Viruses** July 2006 North Carolina Hepatitis A 16 Private property owners allowed travelers to stay on their property and provided drinking water for public use. The drinking water source for the house and the camping area and the water supply for a limited amount of fruits and vegetables was a spring that the owner had excavated. Water was directed into a plastic reservoir above the spring. Untreated water was pumped to the house through a series of pipes and delivered to the downhill camping area through an overflow hose. Water from a spigot from outside the house tested positive for fecal coliforms, E. coli, and hepatitis A. The septic tank located directly upstream from the spring was considered a possible source of water contamination.

July 2006 Maryland Norovirus G1 148 Attendees of a camp developed gastrointestinal illness. Participants were from England, Canada, Australia, Sweden, and the United States(i.e., California, Connecticut, Delaware, Indiana, Illinois, Massachusetts, Maryland, Michigan, New Jersey, New York, and Pennsylvania). Ten persons submitted stool samples, eight of which tested positive for norovirus G1. General concerns included toilet facilities with plumbing deficiencies and limited handwashing stations throughout the camp. The water distribution system did not contain a detectable level of chlorine. Nine of ten water samples from garden hoses used to provide drinking water contained total coliforms and E. coli. Wellconstruction deficiencies were noted (e.g., absence of backflowprevention devices on the pool bath house water heaters and on water distribution lines to the latrines). The well storage tank and latrine wastewater samples contained Norovirus G1; tracer dye added to latrines was detected in the well.

**Parasites** August 2005 California Giardia intestinalis 3 A child’s condition was diagnosed as laboratory-confirmed giardiasis, and a sibling and parent had clinically compatible symptoms. Canal water was piped into a private residence and used for bathing, dishwashing, housecleaning and laundry. Accidental ingestion of contaminated canal water was suspected.

May 2006 Colorado G. intestinalis 6 Participants in a school trip to a state park became ill with gastrointestinal symptoms after consuming inadequately treated river water that was not intended for drinking. Treatment methods included the addition of iodine; filtration; and boiling. No one treatment method was used by the entire group (n=26) and variations in practice were observed among individuals who used each treatment method.

**Mixed Agents** June 2006 Wyoming Norovirus G1, Norovirus G2, 139 Att endees of four week-long camps at a seasonal camp site experienced C. jejuni gastrointestinal illness. Investigators concluded that the camp’s two wells, which were drilled into fractured rock aquifers, may have been contaminated by raw sewage released from the main septic system. Water from the wells repeatedly tested positive for fecal and total coliforms; a septic tank sample tested positive for Norovirus G1 and G2. The main tank was documented as poorly located, at capacity and not meeting the state’s recommended standards for size or type of construction at the time of the outbreak. Well water was not filtered or chlorinated prior to consumption. ( **Source:** CDC, Gastroenteritis among attendees at a summer camp—Wyoming, June-July 2006. MMWR 2007;56(15):368-370)

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**State in No. of**  **which WBDO cases**  **Date occurred Etiologic agent (deaths)**  **Description of WBDO Unidentified**  August 2006 New York Norovirus suspected 16	 Visitors to a bed and breakfast, the owner and his daughter, developed gastrointestinal illness. The incubation period and duration of illness and symptoms were consistent with norovirus infection. The bed and breakfast had its own well and onsite wastewater disposal system, which were located in close proximity. A well water sample was positive for E. coli and might have been contaminated from a poorly maintained, leaking sewage system used by nearby cottages. Year-round residents used onsite septic systems or alternate disposal methods for wastewater when the seasonal system was turned off.The geology of the area was primarily fractured bedrock; contamination of the well likely resulted from waste that was released by the leaking seasonal sewage system or onsite wastewater systems, which then traveled through the rock until it reached the groundwater supply.

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