Surveillance Summaries December 22, 2006 / Vol. 55 / No. SS-12

department of health and human services

Centers for Disease Control and Prevention

Morbidity and Mortality Weekly Report

Surveillance for Waterborne Disease

and Outbreaks Associated with Recreational

Water — United States, 2003–2004

and

Surveillance for Waterborne Disease

and Outbreaks Associated with Drinking Water

and Water not Intended for Drinking —

United States, 2003–2004
MMWR

CONTENTS

Surveillance for Waterborne Disease and Outbreaks

Associated with Recreational Water — United States,

2003–2004

Introduction ..........................................................................2

Background ..........................................................................2

Methods ...............................................................................3

Results .................................................................................5

Discussion .......................................................................... 14

Conclusion ......................................................................... 21

References ......................................................................... 22

Appendices ........................................................................ 25

Surveillance for Waterborne Disease and Outbreaks

Associated with Drinking Water and Water

not Intended for Drinking — United States,

2003–2004

Introduction ........................................................................ 32

Background ........................................................................ 32

Methods ............................................................................. 34

Results ............................................................................... 38

Discussion .......................................................................... 49

Conclusion ......................................................................... 56

References ......................................................................... 56

Appendices ........................................................................ 59

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 2006;55(No. SS-#).

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

Stanley A. Plotkin, MD, Doylestown, PA

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

Anne Schuchat, MD, Atlanta, GA

Dixie E. Snider, MD, MPH, Atlanta, GA

John W. Ward, MD, Atlanta, GA

On the cover: Left to right: Two children, wearing goggles, in a swimming

pool. A man drinking water from a glass. Young girl on boogie board in

water. Drinking fountain with water running.

Centers for Disease Control and Prevention

Julie L. Gerberding, MD, MPH

Director

Tanja Popovic, MD, PhD

(Acting) Chief Science Officer

James W. Stephens, PhD

(Acting) 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

Judith R. Aguilar

(Acting) Director, Division of Health Information Dissemination (Proposed)

Editorial and Production Staff

John S. Moran, MD

(Acting) Editor, MMWR Series

Eric E. Mast, MD, MPH

Guest Editor, MMWR Series

Suzanne M. Hewitt, MPA

Managing Editor, MMWR Series

Teresa F. Rutledge

Lead Technical Writer-Editor

Patricia A. McGee

Project Editor

Beverly J. Holland

Lead Visual Information Specialist

Lynda G. Cupell

Malbea A. LaPete

Visual Information Specialists

Quang M. Doan, MBA

Erica R. Shaver

Information Technology Specialists
Vol. 55 / SS-12 Surveillance Summaries 1

Surveillance for Waterborne Disease and Outbreaks Associated

with Recreational Water — United States, 2003–2004

Eric J. Dziuban1,2

Jennifer L. Liang, DVM1,3

Gunther F. Craun, MPH4

Vincent Hill, PhD1

Patricia A. Yu, MPH5

John Painter, DVM5

Matthew R. Moore, MD6

Rebecca L. Calderon, PhD7

Sharon L. Roy, MD1

Michael J. Beach, PhD1

1Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases (proposed), CDC 2CDC Experience Fellowship, Office of Workforce and Career Development, CDC

3Epidemic Intelligence Service, Office of Workforce and Career Development, CDC 4Gunther F. Craun and Associates, Staunton, Virginia 5Division of Foodborne, Bacterial, and Mycotic Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases (proposed), CDC

6Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases (proposed)

7U.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 waterborne disease and outbreak (WBDO)-related data. 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 WBDOs in the United States.

Reporting Period: Data presented summarize WBDOs associated with recreational water that occurred during

January 2003–December 2004 and one previously unreported outbreak from 2002.

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 associated with drinking water, recreational water, and water not intended for drinking, only cases and outbreaks associated with recreational water are summarized in this report.

Results: During 2003–2004, a total 62 WBDOs associated with recreational water were reported by 26 states

and Guam. Illness occurred in 2,698 persons, resulting in 58 hospitalizations and one death. The median outbreak size was 14 persons (range: 1–617 persons). Of the 62 WBDOs, 30 (48.4%) were outbreaks of gastroenteritis that resulted from infectious agents, chemicals, or toxins; 13 (21.0%) were outbreaks of dermatitis; and

seven (11.3%) were outbreaks of acute respiratory illness (ARI). The remaining 12 WBDOs resulted in primary

amebic meningoencephalitis (n = one), meningitis (n = one), leptospirosis (n = one), otitis externa (n = one), and

mixed illnesses (n = eight). WBDOs associated with gastroenteritis resulted in 1,945 (72.1%) of 2,698 illnesses.

Forty-three (69.4%) WBDOs occurred at treated water venues, resulting in 2,446 (90.7%) cases of illness. The

etiologic agent was confirmed in 44 (71.0%) of the 62 WBDOs, suspected in 15 (24.2%), and unidentified in

three (4.8%). Twenty (32.3%) WBDOs had a bacterial etiology; 15 (24.2%), parasitic; six (9.7%), viral; and

three (4.8%), chemical or toxin. Among the 30 gastroenteritis outbreaks, Cryptosporidium was confirmed as the

causal agent in 11 (36.7%), and all except one of these outbreaks occurred in treated water venues where

Cryptosporidium caused 55.6% (10/18) of the gastroenteritis outbreaks.

In this report, 142 Vibrio illnesses (reported to the Cholera and Other Vibrio Illness Surveillance System) that were

associated with recreational water exposure were analyzed

separately. The most commonly reported species were

Corresponding author: Corresponding author: Michael J. Beach, PhD, Division

of Parasitic Diseases, National Center for Zoonotic, Vector-Borne, and Enteric

Diseases (proposed), 4770 Buford Hwy., NE, MS F-22, Atlanta, GA 30341.

Telephone: 770-488-7763; Fax: 770-488-7761; E-mail: mbeach@cdc.gov.
2 MMWR December 22, 2006

Vibrio vulnificus, V. alginolyticus, and V. parahaemolyticus. V. vulnificus illnesses associated with recreational water

exposure had the highest Vibrio illness hospitalization (87.2%) and mortality (12.8%) rates.

Interpretation: The number of WBDOs summarized in this report and the trends in recreational waterassociated disease and outbreaks are consistent with previous years. Outbreaks, especially the largest ones, are

most likely to be associated with summer months, treated water venues, and gastrointestinal illness. Approximately 60% of illnesses reported for 2003–2004 were associated with the seven largest outbreaks (>100 cases).

Deficiencies leading to WBDOs included problems with water quality, venue design, usage, and maintenance.

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; 2) evaluate the adequacy of efforts (i.e.,

regulations and public awareness activities) to provide safe recreational water; and 3) establish public health prevention priorities that might lead to improved regulations and prevention measures at the local, state, and federal levels.

information described in this report does not include

endemic waterborne disease risks, although studies to measure the levels of endemic illness associated with recreational

water use are needed. Reliable estimates of the number of

unrecognized WBDOs are not available.

Background

Regulation of Recreational

Water Quality

Recreational water use has involved a risk for disease for

virtually all of human history. Evidence of schistosomiasis,

a parasitic disease only contracted by having contact with

contaminated water, can be found in Egyptian mummies

approximately 3,000 years old (13). In the United States,

state and local governments establish and enforce regulations for protecting recreational water from naturally

occurring or human-made contaminants. For treated water

venues (e.g., swimming and wading pools), no federal regulatory agency or national guidelines for standards of operation, disinfection, or filtration exist. Because these swimming

pool codes are developed and enforced by state and local

health departments, substantial variation is observed across

the country in terms of policy, compliance, and enforcement (14). In 1986, EPA published bacterial waterquality criteria for untreated fresh and marine water sources

(15) and made these criteria water-quality standards for

the states and territories that did not adopt the criteria

before 2004. For freshwater (e.g., lakes and rivers), EPA

has recommended criteria that the monthly geometric mean

water-quality indicator concentration be <33 CFU/100 mL

for enterococci or <126 CFU/100 mL for Escherichia coli.

For marine water, EPA has recommended criteria that the

monthly geometric mean water-quality indicator concenIntroduction

During 1920–1970, statistical data regarding waterborne

disease and 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 associated with drinking

water (2–11). In 1978, WBDOs associated with recreational

water were added to the surveillance system. The types of

outbreaks and diseases included in the surveillance summaries have expanded multiple times. Outbreaks of Pontiac

fever (PF) were added in 1989 (9), outbreaks of Legionnaires’

disease were added in 2001 (2), and single cases of Vibrio

illness associated with recreational water but not limited to

preexisting wounds have been added in this report. WBDOs

associated with drinking water and water not intended for

drinking are presented in a separate report (12).

WBDO surveillance activities are intended to 1) characterize the epidemiology of WBDOs; 2) identify changing

trends in the etiologic agents and other risk factors associated with WBDOs; 3) identify major deficiencies in providing safe recreational water; 4) encourage public health

personnel to detect and investigate WBDOs; and 5) foster

collaboration among local, state, federal, and international

agencies on initiatives to prevent waterborne disease. Data

obtained through the WBDOSS are useful for identifying

major deficiencies in providing safe recreational water,

influencing research priorities, supporting public health

recommendations, and encouraging improved waterquality policies and regulations. However, the WBDOs

summarized in this report represent only a portion of the

illness associated with water exposure. The surveillance
Vol. 55 / SS-12 Surveillance Summaries 3

tration be <35 CFU/100 mL for enterococci. However, state

and local authorities have discretionary authority to determine which interventions should be used (e.g., posting signs

to alert visitors of water contamination or closing the beach

for swimming) when these limits have been exceeded. Natural processes to improve the quality of untreated recreational

water might take days to months to occur. In contrast, disinfection, filtration, and pool drainage are examples of techniques that are used to restore a safe swimming environment

in treated water venues. Whereas pools and other treatedwater venues might need to be closed for a period of time

and continued monitoring might be necessary, decontamination is usually feasible in hours to days.

EPA’s Action Plan for Beaches and Recreational Waters

(i.e., Beach Watch) was developed as part of the Clean Water

Action Plan (available at http://www.cleanwater.gov). The

intent of Beach Watch is to assist state, tribal, and local

authorities in strengthening and extending existing programs to protect users of fresh and marine recreational

waters. As part of the Beaches Act of 2000, the U.S. Congress directed EPA to create a new set of guidelines for recreational water based on novel water-quality indicators. As

a result, EPA has been collaborating with CDC since 2002

on a series of epidemiologic studies at fresh and marine

water recreational beaches in the United States. Information on the National Epidemiologic and Environmental

Assessment of Recreational (NEEAR) Water Study is available at http://www.epa.gov/nerlcwww/neearnerl.htm. This

study is being conducted to test rapid new water-quality

methods that are able to produce results in <2 hours and

to correlate these indicators with health effects among

beachgoers. Preliminary results from two 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 (16).

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 the

WBDO, including characteristics of person, place, time,

and results of epidemiologic studies, disease symptoms,

microbiology, and water sampling. Information regarding

the setting of the outbreak also is gathered, including watersupply descriptions, any 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 each coordinator and

conducts as much follow-up correspondence as needed to

resolve unaddressed questions. Contact is made with all

states or localities, including those without WBDO reports.

Information is sometimes solicited from other CDC surveillance systems and confirmed with the state or locality

for inclusion as a WBDO. Outbreaks or cases, where

applicable, are assigned to a state, based on location of

exposure rather than state of residence of ill persons.

Numeric and text data from the CDC form and any supporting documentation are entered into a database for analysis. Although all WBDOs are collected through the same

CDC reporting system, the recreational water-associated

outbreaks are analyzed and published in this report separately from drinking water-associated outbreaks and other

WBDOs (12). SAS programming is used for all statistical

analyses.

Definitions†

The unit of analysis for the WBDOSS is typically an

outbreak, not an individual case of a waterborne disease.

To be defined as a WBDO associated with recreational water,

an event must meet two criteria. First, two or more persons

must be epidemiologically linked by location of exposure

to water, time, and illness. This criterion is waived for 1)

single cases of laboratory-confirmed primary amebic meningoencephalitis (PAM) associated with recreational water,

2) wound infections or other Vibrio infections associated

with recreational water, and 3) single cases of chemical/

toxin poisoning if water or air-quality data indicate contamination by the chemical/toxin. Second, the epidemiologic evidence must implicate water as the probable source

of the illness. WBDOs associated with cruise ships are not

summarized in this report. Recreational water settings

include swimming pools, wading pools, spas, waterslides,

interactive fountains, wet decks, and fresh and marine bodies

of water. For this analysis, the WBDOs are separated by

* 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. † Additional terms have been defined (Appendix A, Glossary of Definitions).
4 MMWR December 22, 2006

venue as untreated (i.e., fresh and marine surface water) or

treated (i.e., disinfected [e.g., chlorinated]) water.

Strength of Evidence Classification

for Waterborne Disease and Outbreaks

WBDOs reported to the 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 waterquality data provided on the WBDO report form.

Although in certain instances WBDOs without waterquality data were included in this report, outbreaks that

lacked 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

optimally conducted nor does a classification of II, III, or

IV imply that an investigation was inadequate or incomplete. Outbreaks and the resulting investigations occur

under different 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 analysis.

Changes in the 2003–2004 Surveillance

Summary

Names, definitions, classifications, and other parameters

in this Surveillance Summary have been modified and

expanded to better reflect the changing epidemiology of

WBDOs and to capture the wide scope of water-related

disease. This section highlights these changes.

Title

The title of this Surveillance Summary has been changed.

Previously titled Surveillance for Waterborne-Disease

Outbreaks Associated with Recreational Water, the title of

the report has been changed to Surveillance for Waterborne

Disease and Outbreaks Associated with Recreational Water.

This subtle difference (“Disease and Outbreaks”) emphasizes the public health importance of certain waterborne

contaminants (e.g., Naegleria, Vibrio, or chemicals) that frequently cause single cases of illness, can be strongly linked

to recreational water exposure, and are reported to the

WBDOSS, despite not being associated with multiple cases

in a traditional “outbreak” setting.

Etiologic Agents

Etiologic agents are identified through clinical specimens

or occasionally by water testing. In previous summaries,

the term “acute gastrointestinal illness (AGI)” was used to

indicate WBDOs of unidentified etiology associated with

gastrointestinal symptoms. Because AGI refers to a type of

illness and not to an etiologic agent, the term “unidentified” is now used to describe WBDOs with unknown

etiology. A classification of “unidentified” might occur for

various reasons, including a lack of clinical specimens, lack

of appropriate testing, or inadequate laboratory capacity. If

more than one agent is implicated, only those that appear

in >5% of positive clinical specimens are included in the

tables and calculations as etiologic agents. When each agent

is of the same agent type (e.g., bacteria, chemicals/toxins,

parasites, and viruses), the outbreak is analyzed within that

agent type (e.g., an outbreak with both Cryptosporidium

and Giardia would be analyzed as a parasitic outbreak).

When agents represent more than one agent type, the outbreak is analyzed as a mixed agent outbreak. All outbreaks

TABLE 1. Classification of investigations of waterborne-disease outbreaks — United States

Class Epidemiologic data Water-Quality data

I Adequate Provided and adequate

Data provided concerning exposed and unexposed Laboratory data or historical information (e.g., the history that a

persons, with relative risk or odds ratio >2 or p<0.05 chlorinator or pH acid feed pump malfunctioned, resulting in no

detectable free-chlorine residual, or a breakdown in a

recirculation system)

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
Vol. 55 / SS-12 Surveillance Summaries 5

in which the etiologic agent is not known or confirmed are

listed as unidentified, and they constitute a separate analysis category from those outbreaks with identified etiologic

agents, even when other data (e.g., clinical findings) are

suggestive of a particular pathogen or chemical/toxin.

In previous Surveillance Summaries, outbreaks in which

patients sought medical care for dermatologic symptoms

consistent with Pseudomonas aeruginosa infection but in

which Pseudomonas was not isolated from clinical specimens

or water samples were still classified as Pseudomonas outbreaks. However, in this report, only those outbreaks in

which clinical specimens or water samples test positive for

Pseudomonas are classified as Pseudomonas outbreaks.

Predominant Illness, Case Counts,

and Deaths

Whereas the illness associated with a WBDO generally

includes only one category of symptoms (e.g., gastroenteritis), WBDOs do occur where the symptoms cluster into

more than one category (e.g., gastroenteritis and dermatitis). Therefore, in this report, if any one illness category is

reported by >50% of ill respondents, then multiple illnesses will be listed for that WBDO. These mixed-illness

WBDOs constitute a separate analysis category from

WBDOs involving a single illness. In addition, the number of deaths associated with each WBDO is now presented

in this report. This change provides increased information

on the severity of illness associated with each WBDO.

Strength of Evidence Classification

for Waterborne Disease and Outbreaks

For the first time, the strength of evidence classification for

WBDOs (Table 1) is used for nongastroenteritis outbreaks

(e.g., dermatitis, PAM, and chemical/toxin poisonings). Classification of these WBDOs should provide a better understanding of the strength of each outbreak investigation.

Vibrio Cases

For the first time, single cases of recreational waterassociated Vibrio illness were selected for inclusion in this

Surveillance Summary by using an algorithm (Figure 1). The

algorithm selected Vibrio cases for inclusion based on previous water exposure in the United States and the absence

of seafood consumption or contact. All selected cases were

verified by the state or local health departments. These

infections frequently were associated with preexisting

wounds but also were associated with other water-related

exposure routes (e.g., wounds incurred while swimming or

walking on the beach or unintentional inhalation of recreational water, resulting in a sinus infection). These cases

are reported to the Cholera and Other Vibrio Illness

Surveillance System on CDC form 52.79 (available at

http://www.cdc.gov/foodborneoutbreaks/documents/

cholera_vibrio_report.pdf). Staff operating the Cholera and

Other Vibrio Illness Surveillance System collaborated with

staff from the WBDOSS to gather all reported recreational

water-associated Vibrio cases for inclusion in this report.

These cases were analyzed separately from other recreational

water illnesses to avoid substantially altering total WBDO

numbers when compared with previous reports. Similarly,

Vibrio cases are also discussed separately in this report.

Results

Excluding Vibrio cases, which are analyzed and discussed

separately, a total of 62 outbreaks (28 in 2003 and 34 in

2004) associated with recreational water were reported to

CDC (Tables 2–5). Of the 50 states and 10 territories,

localities, and FAS participating in the WBDOSS, 27 (26

states and the territory of Guam) reported WBDOs

(Figure 2). Descriptions of selected WBDOs have been presented (Appendix B, Selected Descriptions of Waterborne

FIGURE 1. Algorithm for selection of illnesses associated

with Vibrio isolation and recreational water — United States,

2003–2004*

* Note: Vibrio-related data are only presented in Figures 6–8 and in

Tables 8 and 9.

Persons from whom

Vibrio was isolated

Evidence of seafood or marine life

contact contributing to infection?

Evidence of water exposure in

the United States before infection?

Conflicting data regarding water

exposure before infection? Vibrio

Inclusion in Waterborne Disease

and Outbreak Surveillance System

No

Yes Excluded

Yes

No Excluded

No

Yes Excluded
6 MMWR December 22, 2006

Disease and Outbreaks [WBDOs] Associated with Recreational Water). These 62 outbreaks resulted in 2,698 ill

persons, including one death (attributable to PAM; Table

4). The median outbreak size was 14 persons (range: 1–617

persons). The seven largest outbreaks each had more than

100 ill persons and accounted for 60.3% (n = 1,628) of

the total cases. Illinois reported the highest number of

WBDOs (10), Ohio reported six WBDOs, and Georgia

and Wisconsin both reported five WBDOs.

During 2003–2004, treated water venues were associated with 43 (69.4%) of the recreational water outbreaks

and 2,446 (90.7%) of the cases (Tables 2 and 3; Figure 3).

Untreated venues were responsible for 19 (30.6%) of the

WBDOs but only 252 (9.3%) of the cases (Tables 4 and

5). Similar proportions were identified by venue treatment

type when gastroenteritis outbreaks were analyzed separately (Table 6).

Of the 62 WBDOs, 30 (48.4%) were outbreaks of gastroenteritis, 13 (21.0%) were outbreaks of dermatitis, and

seven (11.3%) were outbreaks of acute respiratory illness

(ARI). The remaining WBDOs resulted in PAM (n = one),

meningitis (n = one), leptospirosis (n = one), otitis externa

(n = one), and mixed illnesses (n = eight) (Table 6, Figure 3).

Gastroenteritis accounted for 1,945 (72.1%) of the cases

of illness. The route of entry implicated for each WBDO

was ingestion for 30 WBDOs (48.4%), contact for 15

(24.2%), inhalation for seven (11.3%), combined routes

for eight (12.9%), other for one (1.6% [Naegleria]), and

unknown for one outbreak (1.6%) (Figure 3).

WBDOs occurred in every calendar month except October, but the summer months (June through August)

accounted for 35 (56.5%) WBDOs and 1,888 (70.0%)

cases (Figure 4). Gastroenteritis was particularly clustered

during these months, in which 22 (73.3%) of 30 outbreaks

and 1,631 (83.9%) of 1,945 cases (Figure 4) were reported.

Treated venues were associated with WBDOs throughout

the year, whereas untreated venue-associated WBDOs

occurred almost exclusively from May through August

(Tables 2–5). Increased reporting of WBDOs occurred

during the summer, with a relative risk (RR) of 3.9 (95%

confidence interval [CI] = 2.4–6.4). This risk increased for

certain outbreak categories. Gastroenteritis outbreaks compared with other illnesses (RR = 8.2; 95% CI = 3.7–18.5)

were especially frequent during the summer (Figure 4).

TABLE 2. Waterborne-disease outbreaks (n = 18) associated with treated recreational water, by state — United States, 2003

Predominant No. of cases

State Month Class* Etiologic agent illness† (n = 1,141) Type Setting

Arkansas Aug IV Cryptosporidium AGI† 4 Pool Large facility

Connecticut Jul I Echovirus 9 Neuro† 36 Pool RV§ campground

Connecticut Aug I MRSA¶ Skin† 10 Spa Athletic center

Georgia Apr IV Unidentified Skin 5 Spa Hotel

Illinois Jan I Pseudomonas aeruginosa Skin 52 Spa Hotel

Illinois Dec I Unidentified** AGI 12 Pool Hotel

Iowa Jun IV Cryptosporidium and Giardia

intestinalis†† AGI 63 Wading pool Day care center

Kansas Jul I C. hominis§§ AGI 617 Pools, Wading pools Community

Massachusetts Jun II G. intestinalis AGI 149 Pool Membership club

Michigan Feb II Unidentified¶¶ Skin 25 Spa Hotel

New Mexico Jun III Legionella pneumophila serogroup 1 ARI† 4 Spa Hotel

New York Mar III Muriatic (hydrochloric) acid ARI 3 Pool Membership club

New York Nov IV Unidentified¶¶ Skin 7 Pool Membership club

Ohio Jan I P. aeruginosa Skin 17 Pool, spa Hotel

Oregon Jul I Shigella sonnei AGI 56 Interactive fountain Community

South Carolina Nov II Unidentified Skin 64 Spa, pool Hotel

Wisconsin Feb I L. pneumophila serogroup 1 ARI 3 Spa Hotel

Wisconsin Jul II Cryptosporidium AGI 14 Wading pool Community

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

cdc_5212_waterborne.pdf).

† AGI: acute gastrointestinal illness; Neuro: neurologic condition or symptoms (e.g., meningoencephalitis or meningitis); Skin: illness, condition, or

symptom related to skin; and ARI: acute respiratory illness.

§ RV: recreational vehicle.

¶ MRSA: Methicillin-resistant Staphylococcus aureus.

** Etiology unidentified; chemical contamination from pool disinfection by-products (e.g., chloramines) suspected.

†† Each pathogen was identified in >5% of positive clinical specimens; therefore, both are listed as etiologic agents. §§ Species determined by using molecular technology and current taxonomic guidelines (Source: Xiao L, Fayer R, Ryan U, Upton SJ. Cryptosporidium

taxonomy: recent advances and implications for public health. Clin Microbiol Rev 2004;17:72–97).

¶¶ Etiology unidentified: P. aeruginosa suspected on the basis of clinical syndrome and setting.
Vol. 55 / SS-12 Surveillance Summaries 7

Etiologic Agents

Of the 62 WBDOs associated with recreational water,

the etiologic agent was confirmed in 44 (71.0%), suspected

in 15 (24.2%) and unidentified in three (4.8%) (Table 7).

Twenty (32.3%) outbreaks were confirmed as bacterial; 15

(24.2%), as parasitic; six (9.7%) as viral; and three (4.8%)

as chemical- or toxin-mediated (Figure 3).

Of the 43 outbreaks associated with treated water venues

that had an identified etiologic agent, 14 (32.6%) involved

bacteria; 12 (27.9%), parasites; four (9.3%), viruses; and

one (2.3%), involved chemicals (Table 7). However, parasites were responsible for more than three times more cases

than bacterial causes (1,414 versus 457). Of the 19 WBDOs

associated with untreated water venues, six (31.6%)

involved bacteria; three (15.8%) parasites; two (10.5%)

viruses; and two (10.5%) toxins. Unlike treated water venues, bacteria were responsible for more than six times more

cases in untreated water venues than parasites (96 versus 14).

Parasites

Of the 30 outbreaks of gastroenteritis, 14 (46.7%) were

parasitic in origin, including 11 (78.6%) caused by

Cryptosporidium, two (14.3%) caused by Giardia intestinalis,

and one (7.1%) caused by both Cryptosporidium and

Giardia (Tables 2–6; Figure 5). Of the 12 gastroenteritis

outbreaks associated with untreated water venues, only two

(16.6%) were caused by parasites. A single Cryptosporidium

outbreak and a single Giardia outbreak each occurred in

untreated lake water, causing four and nine 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 10 (55.6%) of the 18 outbreaks.

A total of 12 parasitic gastroenteritis outbreaks occurred in

treated water venues that caused illness in 1,414 persons.

Four of these outbreaks each caused over 100 (range:

149–617 persons) cases of illness. In June 2003, an

TABLE 3. Waterborne-disease outbreaks (n = 25) associated with treated recreational water, by state — United States, 2004

Predominant No. of cases

State Month Class* Etiologic agent illness† (n = 1,305) Type Setting

California Aug I Cryptosporidium AGI† 336 Pool Water park

Colorado Aug III Cryptosporidium AGI 6 Pool Hotel

Florida May III Norovirus AGI 42 Waterslide School

Georgia Jan IV Unidentified§ Skin† 17 Pool Hotel

Georgia Jun IV Cryptosporidium AGI 14 Pool Community

Idaho Mar II Norovirus AGI 140 Pool Community

Illinois Jan I Unidentified¶ Eye†, ARI† 45 Pool Hotel

Illinois Jan I Unidentified¶ Eye, ARI 22 Pool, spa Hotel

Illinois Feb III Pseudomonas aeruginosa Skin, ARI 16 Pool, spa Hotel

Illinois Feb I P. aeruginosa Skin 5 Spa Hotel

Illinois Mar I Unidentified¶ Eye, ARI 57 Pool, spa Hotel

Illinois Jul IV Unidentified** AGI 9 Pool Community

Illinois Jul I Cryptosporidium AGI 37 Pool, wading pool, Community

interactive fountain

Illinois Sep I Cryptosporidium AGI 8 Pool Hotel

New Mexico Aug IV Unidentified¶ ARI 16 Pool Membership club

New York Dec IV Unidentified¶ ARI 5 Pool Military facility

North Carolina Mar II P. aeruginosa Skin 41 Spa Hotel

Ohio Jul I C. hominis†† AGI 160 Pool, wading pool Community

Ohio Jul I P. aeruginosa Ear†, skin 119 Pool, spa Resort

Ohio Aug I Legionella pneumophila ARI 3 Spa Household

serogroup 1

Oklahoma Mar I L. pneumophila serogroup 1 ARI 107 Spa Hotel

Oregon Mar III P. aeruginosa Skin 2 Spa Motel

Vermont Feb I Norovirus AGI 70 Pool Membership club

Wisconsin Jun I P. aeruginosa Skin, AGI 22 Pool, spa Hotel

Wisconsin Aug IV Cryptosporidium AGI 6 Pool Community

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

cdc_5212_waterborne.pdf).

† AGI: acute gastrointestinal illness; Skin: illness, condition, or symptom related to skin; Eye: illness, condition, or symptom related to eyes; ARI: acute

respiratory illness; and Ear: illness, condition, or symptom related to ears.

§ Etiology unidentified; psychogenic factors and chemical contamination suspected.

¶ Etiology unidentified; chemical contamination from pool disinfection by-products (e.g., chloramines) suspected.

** Etiology unidentified; chemical contamination with pool algaecide suspected.

†† Although both Cryptosporidium oocysts and Giardia cysts were identified in the pool water, only Cryptosporidium oocysts were isolated from clinical

specimens.
8 MMWR December 22, 2006

outbreak of G. intestinalis started at a Massachusetts membership club pool and resulted in 149 cases, including cases

of secondary person-to-person transmission. In July 2003,

a C. hominis outbreak spread in multiple Kansas pools and

day care centers and resulted in 617 cases; this outbreak

was the largest recreational water outbreak during 2003–

2004. In July 2004, an outbreak of Cryptosporidium in a

community pool in Ohio caused gastroenteritis in 160

persons from three counties. In August 2004, employees

ill with gastroenteritis at a California water park continued

working and swimming in the pools, resulting in a

Cryptosporidium outbreak involving 336 persons.

Of the 15 WBDOs of all illness types confirmed to be of

parasitic origin, only one (6.7%) did not involve gastroenteritis; a single fatal case of PAM caused by Naegleria fowleri

occurred in July 2003 at a lake in North Carolina. This case

was the only death reported among the 62 WBDOs during

this reporting cycle (excluding Vibrio cases).

Bacteria

Six reported gastroenteritis outbreaks of confirmed bacterial origin were reported (Figure 5), one of which was at

a treated water venue. This outbreak of Shigella sonnei

occurred in an interactive fountain in Oregon in July 2003,

resulting in 56 cases. Inadequate disinfection, poor monitoring of water chemistry, and heavy use of the fountain by

young diaper-aged children were all cited as factors contributing to the outbreak. The other five bacterial outbreaks

of gastroenteritis were associated with untreated bodies of

water, including two additional outbreaks of Shigella, two

outbreaks of Plesiomonas shigelloides, and one outbreak that

involved both Shigella and Plesiomonas associated with the

use of a lake in Maryland, resulting in illness in 65 persons. Fecal accidents and sewage contamination were

implicated in this outbreak. The other four outbreaks were

substantially smaller; illness occurred in 13 or fewer persons in each outbreak.

TABLE 4. Waterborne-disease outbreaks (n = 10) associated with untreated recreational water, by state — United States, 2003

No. of cases

Predominant (deaths)

State Month Class* Etiologic agent illness† (n = 133) Type Setting

California Jun IV Unidentified§ Skin† 9 Lake Lake

Florida Jul II Unidentified¶ AGI† 10 Lake Lake

Florida May II Unidentified¶ AGI 20 Lake Camp

Georgia May I Shigella sonnei AGI 13 Lake Park

Idaho Jul IV Cryptosporidium AGI 4 Lake Lake

Maryland Jul III S. sonnei & Plesiomonas shigelloides** AGI 65 Lake Park

North Carolina Jul IV Naegleria fowleri Neuro† 1 (1) Lake Lake

Ohio Jul IV P. shigelloides AGI 3 Lake Bathing beach

Ohio Jun IV Unidentified§ Skin 6 Lake Private beach

Wyoming Jul IV P. shigelloides AGI 2 Reservoir Reservoir

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

cdc_5212_waterborne.pdf).

† Skin: illness, condition, or symptom related to skin; AGI: acute gastrointestinal illness; and Neuro: neurologic condition or symptoms (e.g., meningoencephalitis, meningitis).

§ Etiology unidentified; clinical diagnosis of cercarial dermatitis (caused by avian schistosomes).

¶ Etiology unidentified; illness was most consistent with norovirus infection.

** Each pathogen was identified in >5% of positive clinical specimens; therefore, both are listed as etiologic agents.

TABLE 5. Waterborne-disease outbreaks (n = nine) associated with untreated recreational water, by state/territory — United

States, 2004

Predominant No. of cases

State/Territory Month Class* Etiologic agent illness† (n = 119) Type Setting

Arkansas Jun IV Shigella flexneri AGI† 10 Lake Swimming beach

Georgia Aug IV Unidentified Ear† 9 Lake Lake

Guam Apr IV Leptospira species Leptospirosis 3 River Waterfalls

Minnesota Jun IV Norovirus AGI 9 Lake Swimming beach

Missouri Mar IV Giardia intestinalis AGI 9 Lake Lake

Nebraska Jul III Microcystin toxin (blue-green algae) AGI, Skin† 20 Lake Lake

Nebraska Jul III Microcystin toxin (blue-green algae) AGI, Skin 2 Lake Lake

Oregon Jul IV Norovirus AGI 39 Lake Swimming beach

Wisconsin Jul IV Unidentified§ AGI 18 Lake State park

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

cdc_5212_waterborne.pdf).

†AGI: acute gastrointestinal illness; Ear: illness, condition, or symptom related to ears; and Skin: illness, condition, or symptom related to skin.

§Etiology unidentified; Illness was most consistent with norovirus infection.
Vol. 55 / SS-12 Surveillance Summaries 9

Nine of the bacterial outbreaks resulted in cases of dermatitis; for eight of these outbreaks, Pseudomonas aeruginosa

was the confirmed etiologic agent. Three of the eight

Pseudomonas outbreaks were associated with mixed illnesses.

All eight Pseudomonas outbreaks occurred at treated water

venues that involved heated spa water (some of these outbreaks also involved pools), and illness occurred in 274

persons. One outbreak in Ohio in July 2004 involving a

spa and pool accounted for 119 of these cases, which is the

largest bacterial outbreak summarized in this report.

Potential exposure also occurred in this outbreak when the

hotel spa water flowed directly into the swimming pool.

The one bacterial dermatitis outbreak that did not involve

Pseudomonas occurred in August 2003. Multiple members

of a Connecticut college football team were diagnosed with

methicillin-resistant Staphylococcus aureus (MRSA) skin

infections. A spa at the team’s athletic facility, which was

disinfected with an unapproved disinfectant (i.e., povidone),

was implicated in the outbreak.

Four outbreaks caused by Legionella pneumophila were

associated with treated recreational water venues (i.e., spas)

during 2003–2004. Three of these outbreaks

each had fewer than five cases of Legionnaires’

disease. The fourth outbreak, which occurred at

a hotel in Oklahoma during a weeklong basketball tournament in March 2004, included six cases

of Legionnaires’ disease and 101 cases of PF. The

bather load (i.e., maximum occupancy) of the

hotel spa was exceeded, and the bromine concentrations in the spa were not adequately monitored.

An April 2004 outbreak of leptospirosis in

Guam involved three U.S. military personnel who

swam in a remote set of waterfalls. This was the

only outbreak of leptospirosis reported and the

only outbreak reported from outside the 50 states.

Viruses

Six outbreaks of confirmed viral origin occurred,

five of which caused gastroenteritis. In all five of

these gastroenteritis outbreaks, norovirus was

identified as the etiologic agent; two occurred at

lake swimming beaches, and three occurred in

treated water settings. These five norovirus outbreaks resulted in 300 cases of gastroenteritis.

Three other outbreaks were suspected to have

been caused by norovirus contamination. One

outbreak (Idaho, March 2004) occurred during

a swimming competition at a community pool

and resulted in 140 cases. One outbreak (Florida,

FIGURE 2. Number of recreational water-associated outbreaks

(n = 62) — United States, 2003–2004*

* 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.

†Guam also reported one recreational water-associated outbreak in 2004.

>4 (four states)

3 (three states)

2 (seven states)

1 (12 states)†

0 (24 states)

FIGURE 3. Recreational water-associated outbreaks, by type of

exposure, type of etiologic agent, predominant illness, and route of

entry — United States, 2003–2004

*Infection with Naegleria was categorized as other because of the nasal,

noninhalational route of infection.

†Route of transmission for leptospirosis was unclear after investigation.

Type of exposure (n = 62) Type of etiologic agent (n = 62)

Untreated

water

30.6%

Unidentified

29.0%

Viral 9.7%

Parasitic

24.2%

Treated water

69.4% Bacterial

32.3%

Predominant illness (n = 62) Route of entry (n = 62)

Chemical/Toxin

4.8%

Acute

gastrointestinal

illness

48.4%

Multiple

12.9%

Ear infection 1.6%

Leptospirosis 1.6%

Neurologic 3.2%

Acute

respiratory

infection

11.3%

Dermatitis

21.0%

Unknown 1.6% †

Contact

24.2%

Ingestion

48.4%

Other* 1.6%

Inhalation

11.3%

Combined

routes

12.9%
10 MMWR December 22, 2006

May 2004, norovirus etiology) involved an elementary

school that used an outdoor hose to supply waterslides

during outdoor play time. Children were infected after one

ill child with diarrhea used one of the slides; secondary

transmission to household contacts also occurred, resulting in 42 cases.

In July 2003, a viral outbreak of meningitis occurred in a

pool at a Connecticut campground. Echovirus 9, an

enterovirus, was isolated from patient cerebrospinal fluid

samples. Although aseptic meningitis occurred in 12 of 36

persons, a wide range of other symptoms were reported by

the other 24 ill persons, including headache and rash.

Chemicals/Toxins

During 2003–2004, three outbreaks involving chemicals or toxins resulted in 25 ill persons. One outbreak

occurred in a treated water venue. In March 2003, muriatic (i.e., hydrochloric) acid, used for pH control in recreational water, spilled on the floor at an indoor pool in New

York and resulted in exposure to toxic fumes, which led to

respiratory distress in three persons who sought emergency

department medical care.

During 2004, two toxin-associated outbreaks occurred

in untreated water venues in Nebraska. These outbreaks

were attributed to elevated levels of microcystin toxin (17)

from blue-green algae (i.e., cyanobacteria) in lakes, causing 22 cases of illness. The predominant illnesses in both

outbreaks involved dermatitis and gastroenteritis. Patients

who sought medical care had a combination of rashes,

diarrhea, cramps, nausea, vomiting, and fevers.

Unidentified Etiologic Agents

Eighteen outbreaks occurred in which no etiologic agent

was confirmed; however, in 15 of these outbreaks, investigation reports described a suspected agent, based on symptoms, setting, and circumstances (Table 7). Of these 18

outbreaks, seven reported skin infections, five reported gastroenteritis, three reported mixed-eye and ARI, two reported

ARI, and one reported ear infections. Eight of these 15

outbreaks were suspected to be related to chemical exposure. For one of these outbreaks (Georgia, January 2004),

psychogenic factors also were suspected to play a role in

the 17 cases of dermatitis because certain rashes resolved

before first responders arrived to investigate. Another outbreak of gastroenteritis was suspected to be a result of the

application of a pool algaecide before swimmers entered

the pool. The six remaining outbreaks all were suspected

to involve exposure to excess chloramines (i.e., disinfection

by-products of chlorination) (18–20) in the indoor pools

and surrounding areas (i.e., indoor pool air), which resulted

TABLE 6. Number of waterborne-disease outbreaks (n = 62) associated with recreational water, by predominant illness and type

of water — United States, 2003–2004

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 18 1,743 12 202 30 (48.4) 1,945 (72.1)

ARI 7 141 0 0 7 (11.3) 141 (5.2)

Ear 0 0 1 9 1 (1.6) 9 (0.3)

Ear and Skin 1 119 0 0 1 (1.6) 119 (4.4)

Eye and ARI 3 124 0 0 3 (4.8) 124 (4.6)

Leptospirosis 0 0 1 3 1 (1.6) 3 (0.1)

Neurologic 1 36 1 1 2 (3.2) 37 (1.4)

Skin 11 245 2 15 13 (21.0) 260 (9.6)

Skin and AGI 1 22 2 22 3 (4.8) 44 (1.6)

Skin and ARI 1 16 0 0 1 (1.6) 16 (0.6)

Total (%) 43 (69.4) 2,446 (90.7) 19 (30.6) 252 (9.3) 62 (100.0) 2,698 (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; and Neuro: neurologic condition or symptoms (e.g., meningoencephalitis, meningitis).

FIGURE 4. Number of recreational water-associated outbreaks

(n = 62), by predominant illness and month — United States,

2003–2004

* A combination of illnesses.

Mixed*

Leptospirosis

Ear infection

Neurologic

Respiratory

Skin

Gastroenteritis

0

4

8

12

16

20

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

Month

No. of outbreaks
Vol. 55 / SS-12 Surveillance Summaries 11

in ARI, eye irritation, and gastroenteritis. P. aeruginosa was

the suspected pathogen in two dermatitis outbreaks in

treated water venues. Norovirus was the suspected pathogen in three gastroenteritis outbreaks at lakes, based on

epidemiologic and clinical evidence. Two outbreaks were

suspected to be the result of contact with avian schistosomes, causing cercarial dermatitis.

Information regarding the remaining three outbreaks of

unidentified etiology was not sufficient to suggest an etiologic agent. Skin infections were reported as the predominant illness in two of these outbreaks, and ear infections

were reported for the third one. Two outbreaks of skin

infections were associated with spas. One resulted in 64 ill

persons, but water sampling could not be conducted

because the spa had been drained for routine maintenance

before the investigation (South Carolina, November 2003).

The third outbreak resulted in ear infections in nine children (Georgia, August 2004) who had been swimming and

submerging their heads in a lake.

Vibrio Cases Associated with

Recreational Water

During 2003–2004, a total of 142 Vibrio cases associated with recreational water were reported from 16 states.

Recreational water-associated Vibrio cases were defined as

those with recreational water exposure in the United States

before infection and with no evidence that contact with

seafood or marine life might have caused infection

(Figure 1). Among patients for whom information was available, 70 (49.3%) of 142 were hospitalized, and nine (6.3%)

of 142 died (Table 8).

The most frequently isolated Vibrio species was

V. vulnificus, which was isolated from 47 (33.1%) persons;

41 (87.2%) were hospitalized, and six (12.8%) died.

V. alginolyticus was isolated from 43 (30.2%) persons; eight

(18.6%) were hospitalized, and one (2.3%) died.

V. parahaemolyticus was isolated from 34 (23.9%) persons;

15 (44.1%) were hospitalized, and none died. Other Vibrio

species (including noncholerigenic V. cholerae, V. damsela,

TABLE 7. Number of waterborne-disease outbreaks (n = 62) associated with recreational water, by etiologic agent(s) and type of

water — United States, 2003–2004

Type

Treated Untreated Total

No. of No. of No. of No. of No. of No. of

Etiologic agent outbreaks cases outbreaks cases outbreaks (%) cases (%)

Bacteria 14 457 6 96 20 (32.3) 553 (20.5)

Legionella pneumophila 4 117 0 0 4 117

Leptospira species 0 0 1 3 1 3

MRSA* 1 10 0 0 1 10

Plesiomonas shigelloides 0 025 2 5

Pseudomonas species 8 274 0 0 8 274

Shigella species 1 56 2 23 3 79

Shigella and Plesiomonas species 0 0 1 65 1 65

Parasites 12 1,414 3 14 15 (24.2) 1,428 (52.9)

Cryptosporidium species 10 1,202 1 4 11 1,206

Giardia species 1 149 1 9 2 158

Naegleria fowleri 0 011 1 1

Cryptosporidium and Giardia species 1 63 0 0 1 63

Viruses 4 288 2 48 6 (9.7) 336 (12.5)

Echovirus 9 1 36 0 0 1 36

Norovirus 3 252 2 48 5 300

Chemicals/toxins 1 3 2 22 3 (4.8) 25 (0.9)

Microcystin toxin (blue-green algae) 0 0 2 22 2 22

Muriatic acid 1 3 0 0 1 3

Unidentified agent 12 284 6 72 18 (29.0) 356 (13.2)

Suspected chemicals† 1 17 0 0 1 17

Suspected chloramines 6 157 0 0 6 157

Suspected algaecide 1 9 0 0 1 9

Suspected norovirus 0 0 3 48 3 48

Suspected Pseudomonas species 2 32 0 0 2 32

Suspected schistosomes 0 0 2 15 2 15

Other unidentified 2 69 1 9 3 78

Total (%) 43 (69.4) 2,446 (90.7) 19 (30.6) 252 (9.3) 62 (100.0) 2,698 (100.0)

* Methicillin-resistant Staphylococcus aureus. †Suspected psychogenic factors and chemical exposure.
12 MMWR December 22, 2006

V. fluvialis, nonspeciated Vibrio, and mixed Vibrio species)

were identified in 18 (12.7%) persons; six (33.3%) were

hospitalized, and two (11.1%) died. Six patients were

reported to have had an amputation; five were infected with

V. vulnificus; and one with V. parahaemolyticus.

Other bacterial species also were identified with Vibrio;

25 (25.3%) of 99 Vibrio isolates for which information was

available yielded other bacterial species. These other species included E. coli, Pseudomonas species,

Staphylococcus marcescens, S. aureus, and Streptococcus. Of the 149 Vibrio isolates taken from

142 patients, 85 (57%) were from wounds,

31 (20.8%) from blood, 27 (18.1 %) from

ears, and six (4%) from other sites (i.e., chest

abscess, eye, incision, sinus, sputum, stool,

and urine).

Geographic location. Nearly all Vibrio

patients reported that they were exposed to

recreational water in a coastal state (Figure 6).

The most frequently reported location was

the Gulf Coast (62.7%); Pacific Coast states

(19.7%); Atlantic Coast states, excluding

Florida (16.9%); and inland states (0.7%)

(Table 9). Florida, Hawaii, and Texas reported

the highest number of cases, 51, 23, and 28

cases, respectively (Figure 6; Table 9).

Seasonality. In the temporal distribution

of illness in patients from whom Vibrio species were isolated, a clear seasonal peak

occurred during the summer (Figure 7). The

greatest frequency of Vibrio cases occurred

during July and August for all species.

Exposures. Activities associated with Vibrio

cases included swimming, diving, or wading in water

(66.9%); walking or falling on the shore or rocks (32.3%);

and boating, skiing, or surfing (21.8%). The majority of

patients reported being exposed in the ocean (100 [70.4%]);

12 (8.5%) were exposed in a river, stream, or creek; seven

(4.9%) were exposed in a lake or bay; eight (5.6%) were

exposed to another water source; and 15 (10.6%) exposed

a wound to an unknown water source.

TABLE 8. Number of illnesses associated with Vibrio isolation (n = 142) and recreational water exposure, by species and year —

United States, 2003–2004

Year

2003 2004 Total

Species Cases Hospitalized Deaths Cases Hospitalized Deaths Cases Hospitalized Deaths

Vibrio alginolyticus 24 4 1 19 4 0 43 8 1

V. cholerae non-O1, non-O139 3 0 0 4 2 1 72 1

V. cholerae, unknown type 0 0 0 1 0 0 10 0

V. damsela 10 0 11 0 21 0

V. fluvialis 11 0 00 0 11 0

V. parahaemolyticus 12 4 0 22 11 0 34 15 0

V. vulnificus 20 20 1 27 21 5 47 41 6

Multiple* 0 0 0 1 1 0 11 0

Vibrio, species not identified 2 0 0 4 1 1 61 1

Total (% of cases) 63 29 (46.0%) 2 (3.2%) 79 41 (51.9%) 7 (8.9%) 142 70 (49.3%) 9 (6.3%)

Percentage by year (44.4) (41.4) (22.2) (55.6) (58.6) (77.8) (100.0) (100.0) (100.0)

* V. alginolyticus/V. parahaemolyticus coinfection.

FIGURE 5. Recreational water-associated outbreaks of gastroenteritis, by

type of exposure and etiologic agent — United States, 2003–2004

* For one of these outbreaks, cysts of Giardia species and oocysts of Cryptosporidium

species were identified in pool water, but only Cryptosporidium was identified in the

tested clinical samples.

Type of exposure (n = 30) Etiologic agent (n = 30)

Untreated

water

40.0%

Treated

water

60.0%

Etiologic agent: untreated water (n = 12) Etiologic agent: treated water (n = 18)

Cryptosporidium spp.* 36.7%

Shigella

Plesiomonas

and

spp.

3.3%

Cryptosporidium

and spp. Giardia

3.3%

Unidentified

16.7%

Norovirus

16.7%

Shigella spp.

10.0%

Plesiomonas spp.

Giardia spp. 6.7%

6.7%

Plesiomonas

shigelloides

16.7%

Shigella spp.

16.7%

Unidentified,

suspected

norovirus

25.0%

Shigella

Plesiomonas

and

spp.

8.3%

Giardia spp.

8.3%

Cryptosporidium

spp. 8.3%

Norovirus

16.7%

Unidentified,

suspected chemical

11.1%

Shigella sonnei

5.6%

Giardia intestinalis

5.6%

Cryptosporidium

spp.* 55.6%

Norovirus

16.7%

Cryptosporidum

and spp. Giardia

5.6%
Vol. 55 / SS-12 Surveillance Summaries 13

Symptoms. Symptoms associated with Vibrio cases were

cellulitis (54.9%), fever (41.5%), muscle pain (24.6%),

ear infection (19.0%), nausea (18.3%), shock (12.7%),

and bullae (12.0%) (Figure 8). V. vulnificus accounted for

the majority of skin infections, including cellulitis, bullae,

and other skin infections (56 [51.9%] of 108). V. vulnificus

also accounted for the majority of severe illnesses, including those with fever (79.5%), bacteremia (80.6%), and

shock (66.7%). V. alginolyticus accounted for the majority

of ear infections (17 [63.0%] of 27). Other symptoms and

infections were reported in low frequencies (e.g., bladder

infections, hematuria, eye infections, respiratory symptoms,

sinus infections, diarrhea, and vomiting).

Previously Unreported Outbreak

One previously unreported recreational water outbreak

from 2002 was received. The outbreak is summarized but

not analyzed in this Surveillance Summary. The outbreak

occurred in Florida in December 2002 and involved two

TABLE 9. Number of recreational water-associated Vibrio isolations and deaths, by region/state and species — United States,

2003–2004

Species

V. alginolyticus V. parahaemolyticus V. vulnificus Other/unknown species* Total

Region/State Cases Deaths Cases Deaths Cases Deaths Cases Deaths Cases Deaths

Atlantic

Connecticut 0 0 1 0 0 0 0 0 1 0

Georgia 1 0 0 0 0 0 1 0 2 0

Maryland 2 1 1 0 2 0 0 0 5 1

North Carolina 2 0 2 0 1 0 2 0 7 0

New Jersey 0 0 1 0 0 0 0 0 1 0

New York 2 0 0 0 0 0 0 0 2 0

Rhode Island 1 0 0 0 0 0 0 0 1 0

Virginia 1 0 2 0 2 0 0 0 5 0

Total 9 1 7 0 5 0 3 0 24 1

Gulf Coast

Alabama 0 0 0 0 1 0 0 0 1 0

Florida† 9 0 17 0 21 2 4 0 51 2

Louisiana 0 0 0 0 6 1 0 0 6 1

Mississippi 1 0 1 0 1 1 0 0 3 1

Texas 5 0 6 0 8 1 9 2 28 3

Total 15 0 24 0 37 5 13 2 89 7

Noncoastal

Kansas 0 0 0 0 0 0 1 0 1 0

Total 0 0 0 0 0 0 1 0 1 0

Pacific

California 4 0 0 0 0 0 1 0 5 0

Hawaii 15 0 3 0 5 1 0 0 23 1

Total 19 0 3 0 5 1 1 0 28 1

Total 43 1 34 0 47 6 18 2 142 9

Percentage (30.3) (11.1) (23.9) (0) (33.1) (66.7) (12.7) (22.2) (100.0) (100.0)

* Includes V. cholerae (non-O1, non-O139, and unknown serotype), V. damsela, V. fluvialis, V. alginolyticus/V. parahaemolyticus coinfection, and Vibrio

species not identified.

†Five reports from Florida indicate Atlantic coast exposure.

FIGURE 6. Number of illnesses associated with Vibrio isolation

and recreational water exposure (n = 142) — United States,

2003–2004*

* 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.

>10 (three states)

5–9 (five states)

2–4 (three states)

1 (five states)

0 (34 states)
14 MMWR December 22, 2006

laboratory-confirmed cases of Legionnaires’ disease (i.e.,

Legionella pneumophila serogroup 1) linked to a hotel spa.

Both persons were hospitalized and recovered. No

Legionellae were recovered from the spa, but epidemiologic

evidence (Class III) implicated the spa as the probable source

for this cluster of cases. Bromine tablets were used to disinfect the spa, but the tablets did not dissolve properly, leading to low bromine concentrations in the water and

conditions favorable for the growth of Legionella.

Discussion

Trends in Reporting Outbreaks

A total of 62 recreational water-associated WBDOs were

reported to CDC during 2003–2004. This number is a

slight decrease from the previous 2001–2002 Surveillance

Summary in which a record number (65) of WBDOs were

reported. Both the number of reported recreational waterassociated WBDOs (Pearson’s correlation = 0.59; p<0.01)

and outbreaks of gastroenteritis (Pearson’s correlation = 0.86;

p<0.01) have increased significantly since 1978 when

CDC first began receiving these reports (Figure 9). These

increases are likely 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 of recreational water-associated

outbreaks also might be contributing factors.

The number of reported WBDOs also differs substantially

based on geographic location (Figure 2). This variation might

be a result of several factors, including public awareness of

the outbreak, availability of laboratory testing, requirements

for reporting diseases, and resources available to local and

state health departments for surveillance and investigation

of probable outbreaks. Differences in the capacity of local

and state public health agencies and laboratories to detect

WBDOs probably result in 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

FIGURE 7. Number of illnesses associated with Vibrio isolation

and recreational water (n = 142), by species and month — United

States, 2003–2004

* Includes noncholeragenic V. cholerae (eight), V. damsela (two),

V. fluvialis (one), V. alginolyticus/V. parahaemolyticus coinfection (one),

and Vibrio species not identified (six).

0

5

10

15

20

25

30

35

Other species* (n = 18)

(n = 34)

(n = 43)

(n = 47)

V. parahaemolyticus

V. alginolyticus

V. vulnificus

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

Month

No. of cases

FIGURE 8. Number of illnesses associated with Vibrio isolation

and recreational water (n = 142), by selected clinical outcomes

and species — United States, 2003–2004

*Includes noncholeragenic V. cholerae, V. damsela, V. fluvialis,

V. alginolyticus/V. parahaemolyticus coinfection, and Vibrio species

not identified.

0

20

40

60

80

100

Amputation

Bacteremia

Bullae

Cellulitis

Ear infection

Fever

Muscle pain

Nausea

Shock

Clinical outcomes

No. of cases

Other spp.*

V. parahaemolyticus

V. alginolyticus

V. vulnificus

FIGURE 9. Number of recreational water-associated outbreaks

(n = 508), by year and illness — United States, 1978–2004

* Includes keratitis, conjunctivitis, otitis, bronchitis, meningitis, hepatitis,

leptospirosis, Pontiac fever, acute respiratory illness, and combined

illnesses.

†Also includes data from report of ameba infections (Source: Visvesvara

GS, Stehr-Green JK. Epidemiology of free-living ameba infections.

J Protozool 1990;37:25S–33S).

0

15

30

45

1978 1982 1986 1990 1994 1998 2002

Year

No. of outbreaks

Other*

Skin

Meningoencephalitis

Gastroenteritis

†
Vol. 55 / SS-12 Surveillance Summaries 15

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 practices.

Multiple other factors also might influence which WBDOs

are reported. Larger outbreaks are more likely to be identified by public health authorities and to receive more rigorous investigations. Etiologic agents with shorter incubation

periods might be more easily linked to water exposures,

facilitating the recognition of outbreaks. In contrast, private

residential pools and spas might experience problems that

go undetected because they are not regulated or inspected

by public health agencies. In addition, outbreaks of gastroenteritis at large venues that draw from a wide geographic

range (e.g., the Great Lakes and ocean 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. Such an

effect is supported by data from EPA’s NEEAR Water Study

(16). This prospective study of large beaches on the Great

Lakes has indicated that elevated rates of gastroenteritis have

occurred in swimmers compared with nonswimmers on all

four beaches studied, although outbreaks associated with the

use of the beaches were not reported during this period. Consistent with this finding, WBDOs reported in Surveillance

Summaries have not been ocean beach-associated outbreaks

of gastroenteritis, and only one Great Lakes

beach-associated outbreak of gastroenteritis has been reported since 1978 (2).

Multiple other prospective studies of

gastroenteritis associated with beach

swimming have also indicated elevated

rates of illness associated with swimming

(21). This endemic recreational waterassociated illness is not captured by the

WBDOSS, supporting the need for more

studies to be conducted to determine the

magnitude of risk of illness for routine,

nonoutbreak-associated exposures at recreational water venues.

WBDOs associated with recreational

water use occur year-round, but the number of reported WBDOs and cases are

highest during the annual summer swim

season (Figure 4). For public health professionals, these trends can help determine

the allocation of resources so that health

education messages are targeted to populations during times of the year when the

highest risk for preventable illness occurs.

Swimming Pools

Infectious Gastroenteritis

During 2003–2004, Cryptosporidium caused the largest

number of recreational water-associated outbreaks (n = 11).

These outbreaks accounted for the largest number of ill

persons included in this report (n = 1206); 99.7% of these

cases were associated with treated water venues. During

1995–2004, Cryptosporidium was implicated in 39.0% of

the recreational water-associated outbreaks of gastroenteritis and, although Cryptosporidium rarely was attributed to

outbreaks in lakes and rivers (10% of outbreaks), it caused

61.8% of outbreaks associated with treated venues

(Figure 10). This observation for treated venues is consistent with the finding that Cryptosporidium requires extended

contact time with chlorine for inactivation; oocysts can

survive for days in the chlorine levels that typically are recommended for swimming pools (1–3 ppm free chlorine;

22). The continued reporting of cryptosporidiosis associated with the use of treated water venues underscores the

importance of other prevention measures that reach beyond

traditional pool chlorination, which is currently the primary barrier to infectious disease transmission.

Cryptosporidiosis has stimulated the need for new technology to keep swimming venues safe (e.g., ultraviolet light

irradiation, ozonation, chlorine dioxide use, or improved

FIGURE 10 . Recreational water-associated outbreaks of gastroenteritis, by type

of exposure and etiologic agent — United States, 1995–2004

* These include outbreaks of Salmonella, Campylobacter, Plesiomonas, and mixed pathogens.

Etiologic agent: untreated water (n = 60) Etiologic agent: treated water (n = 76)

Shigella spp.

11.7%

Giardia spp. 5.0%

Cryptosporidium

spp. 10.0%

Norovirus

16.7%

E. coli

23.3%

Unidentified

28.3%

Other*

5.0% Unidentified

10.5%

Other* 3.9%

Giardia spp. 2.6%

E. coli 5.3%

Shigella spp.

7.9%

Norovirus

7.9% Cryptosporidium

spp. 61.8%

Etiologic agent (n = 136)

Cryptosporidium

spp. 39.0%

Unidentified

18.4%

Norovirus

11.8%

Shigella spp.

9.6%

Escherichia coli

13.2%

Other* 4.4%

Giardia spp. 3.7%

Type of exposure (n = 136)

Untreated

water

44.1%

Treated

water

55.9%
16 MMWR December 22, 2006

filtration). However, cryptosporidiosis outbreaks also highlight the need for improved operator training and continued education of the general public concerning appropriate

healthy swimming practices to reduce the risk of future

outbreaks.

Because Cryptosporidium is resistant to the chlorine levels

used in pools, outbreaks can occur, even in facilities that

are well-maintained. Therefore, a rapid public health

response and increased community involvement is needed

to prevent the expansion of these outbreaks (23). The

Cryptosporidium outbreak (Ohio, July 2004) that occurred

in a community swimming pool demonstrates that a rapid

communitywide public health response during the early

stages of an outbreak can help control the potential spread

of illness into the community. In Ohio, detection and

investigation started during the second week after exposure. The response included mitigating actions (e.g.,

hyperchlorination of all pools and providing instructions

regarding proper water hygiene to pool staff and users, day

care centers, restaurants, and other potentially affected

facilities). In addition, the investigation indicated that no

transmission had apparently occurred outside of the single

community pool. In contrast, the outbreak in Kansas (July

2003) was not detected for multiple weeks. As a result, a

full communitywide outbreak occurred when ill pool

patrons and daycare center attendees continued their normal activities (despite their illness) exposing large numbers of persons to Cryptosporidium.

Approximately 60% of all cases of illness reported to this

surveillance system during 2003–2004 were associated

with infectious gastroenteritis outbreaks in treated pools.

Several of these outbreaks (e.g., giardiasis, norovirus, and

echovirus) could have been prevented or reduced in scale

by using proper pool disinfectant procedures and by

following existing operation, maintenance, and communication protocols because of the pathogens’ chlorine sensitivities. The norovirus outbreak (Vermont, February 2004)

demonstrated that when pool staff do not follow these protocols, outbreaks might occur. Despite complaints from

patrons concerning water quality, on-duty staff failed to

alert off-duty pool operation personnel. As a result, a malfunctioning chlorinator system was not detected for several

days; norovirus transmission occurred for multiple days

(which probably would have been hours or less with proper

chlorination) before the breakdown was discovered and corrected (24). This outbreak emphasizes the need for both

effective communication channels at aquatic facilities and

trained personnel on site or accessible on weekends when

pool use is highest.

Swimming behavior is also a critical component of pool

operation. Because swimming is essentially communal bathing, when persons who are ill with infectious diarrhea continue to swim, a public health challenge is created that

requires a focused public education effort. In addition,

improved hygiene is essential to ensure the cleanliness of

swimmers entering pools. Functioning and adequate

hygiene facilities (i.e., toilets, diaper-changing areas, and

showers) in adequate numbers should be located near pools

and should provide hot water and handwashing access.

Swimmers should be encouraged to shower thoroughly (i.e.,

washing the perianal surface in particular) before entering

the pool. Diaper-changing facilities, with hand-washing

stations, should be readily accessible to prevent diaperchanging at the poolside. These outbreaks demonstrate how

pools can serve as ideal amplification venues for fecal-oral

transmission of pathogens. As a result, facilities should be

diligent about making patrons aware of these public health

concerns and about making clear that “no diarrhea” policies apply to all pools. This policy is especially needed for

young children visiting pools, particularly large groups (e.g.,

day care centers), which already have diarrhea exclusion

policies but might not always enforce them (Kansas, July

2003). Diarrhea exclusion policies should apply to both

pool employees when swimming and food workers when

preparing food. For the waterpark-associated outbreak in

California (August 2004), documentation revealed that

employees were ill with diarrhea before the main outbreak,

which involved patrons, and that employees admitted to

swimming while symptomatic. All aquatic facilities need

to establish standardized policies for keeping staff who are

ill with diarrhea out of pools and should subsequently implement and enforce these policies.

Meningitis

Although gastroenteritis is the most common illness

spread via pool outbreaks, it is not the only disease that

can be contracted in this manner. In one outbreak, the transmission of an agent causing viral meningitis via a swimming pool at a recreational vehicle campground

(Connecticut, July 2003) was reported. The implicated

enterovirus, Echovirus 9, was the predominant enterovirus

serotype circulating through the eastern United States during 2003 and is susceptible to chlorine if proper chlorine

residuals are maintained (25). Properly monitored and

maintained chlorination levels and pH control in pools

should prevent this type of WBDO.
Vol. 55 / SS-12 Surveillance Summaries 17

Chemical Toxicity

During 2003–2004, pool chemicals or disinfection

by-products were confirmed (n = one) or suspected (n =

eight) in nine pool-associated outbreaks. Chemicals are

added to pool water to protect against microbial growth

and improve the water quality and efficacy of the disinfection process (e.g., pH control). However, these same chemicals can become sources of illness if they are not properly

handled or if water quality and ventilation are poor. One

outbreak in New York (March 2003) involved an overflow

and spill of muriatic (i.e., hydrochloric) acid, which is used

for pH control of pool water. As a result, three persons

developed ARI from exposure to fumes. Another outbreak

(Illinois, July 2004) was suspected to be caused by ingestion of algaecide that was added to the pool before a swim

meet, which resulted in nine persons becoming ill with

gastroenteritis. These outbreaks underscore the need for safe

chemical training (i.e., adding disinfectant, controlling pH

levels, and using pool additives appropriately), handling,

and safety practices at all aquatic facilities to protect the

health of patrons and staff. These policies should include

proper handling of chemicals in the pump room and

application procedures for adding pool chemicals directly

to the pool.

Six outbreaks of acute respiratory symptoms, eye irritation, and gastroenteritis were suspected to be a result of an

accumulation of chloramines in the air and water of indoor

pools. Chloramines are disinfection by-products that

result from chlorine oxidation of nitrogenous waste compounds, commonly shed into pools by swimmers (e.g.,

perspiration, saliva, urine, and body oils) (18). These chemicals are produced in the water and volatilize in the air. In

indoor pool settings, chloramines can also accumulate in

the enclosed spaces if ventilation is inadequate (19). The

resulting high levels of chloramines can cause respiratory

tract and mucous membrane irritation (20); these high levels

also are potentially linked to asthma in indoor pool settings (26).

Because of the shortage of laboratories that perform analyses for airborne chloramines and because of rapid shifts in

indoor air quality over days, the investigators’ ability to

respond to reports of airborne chloramines and to quantitatively identify these chemicals is difficult. Investigators

should always document the easily measured total chlorine concentration (i.e., free plus combined chlorine) and

free chlorine levels of the pool water to obtain some indication of pool water quality and the potential for the presence of disinfection by-products, especially chloramines,

which might be present in the water and air.

Multiple steps can be taken to address indoor pool problems, including swimmer behavior modification. Encouraging showering before entering any pool or spa and

facilitating frequent bathroom breaks for swimmers, particularly young children (i.e., by instituting adult-only

swim times and short closures for water-quality testing),

might reduce the amount of 1) urine and other nitrogenous waste contaminating the water and 2) accumulation

of chloramines. To encourage swimmers to refrain from urinating in public pools, they should be educated that stinging eyes from pool chemicals are actually caused by human

waste (i.e., urine and sweat) in the pool water. Improved

indoor pool ventilation is vital to increase air-turnover and

to remove concentrated chloramines; however, new studies

have suggested that installation of ultraviolet light treatment devices in pool water recirculation systems can

reduce pool chloramine levels and inactivate chlorine-resistant pathogens (e.g., Cryptosporidium) (27,28).

Surveillance for recreational water-associated outbreaks

of acute chemical poisonings is likely to have multiple barriers; therefore, the number of reported chemical/toxin

WBDOs probably underestimates the true magnitude of

the problem. Symptoms associated with chemical poisonings in recreational water settings might be substantially

different from those associated with more familiar infectious microbes, which might lead to decreased chemicalrelated WBDO identification. By contrast, chemicals/toxins

and infectious agents might cause similar symptoms (e.g.,

gastrointestinal illness), and investigators might fail to identify the etiologic agent because they do not suspect a chemical etiology. Multiple health departments use infectious

disease epidemiologists for WBDO surveillance and investigation. However, chemical-related WBDOs and recreational WBDOs, in general, might be investigated by staff

from different sections of the health department or by staff

from different agencies. Because of the acute nature of certain chemical-related WBDOs, first responders will likely

be called to the scene, and persons from these agencies

might be less likely to report back through the traditional

chain of health department infectious disease epidemiologists who report to the WBDOSS. Therefore, building

strong and effective intra- and interagency communication

networks between health departments and other groups

(e.g., first responders and pool operators) to reduce the

underreporting of recreational WBDOs is critical.

Spas

Spas are susceptible to contamination from persons

infected with the same pathogens that cause gastroenteritis
18 MMWR December 22, 2006

in swimming and wading pools. However, the increased

temperature of the water also makes these venues susceptible to contamination with and amplification of thermophilic pathogens (e.g., Pseudomonas and Legionella) that

naturally occur in the environment (i.e., contamination does

not necessarily occur via ill swimmers).

Skin Infections

Spa-associated outbreaks are commonly associated with

dermatitis and folliculitis; P. aeruginosa is the most commonly reported agent implicated in these settings (29). In

this report, eight confirmed Pseudomonas WBDOs and two

suspected Pseudomonas WBDOs were documented; five of

these outbreaks involved spas, one involved a pool, and four

involved both spas and pools. Because of the frequent use

of both spas and pools at the facilities, determining whether

the spa, pool, or both are implicated in transmission of

illness is epidemiologically difficult, although amplification of Pseudomonas is more likely to occur in the higher

temperatures of spas. One outbreak report (Ohio, July

2004) concluded that Pseudomonas growing in a spa was

transferred to a pool through combined water circulation

and that infection occurred in both settings.

Spas are a challenge to maintain and operate because they

typically have reduced bather capacity compared with

swimming pools, so they can more easily be overloaded

and rapidly lose disinfectant concentrations when bather

loads exceed recommended numbers of persons. In addition, depletion of disinfectant levels is increased at higher

temperatures. Large gatherings at hotels and motels with

spas (e.g., cheerleading competitions [North Carolina,

March 2004], dance competitions [Ohio, July 2004], and

school class outings [Michigan, February 2003]) can rapidly overload the disinfection capacity and lead to bacterial

amplification. In addition to overloading the spas and

depleting the disinfectant, these groups frequently arrive

on weekends when hotel staff trained in spa maintenance

are off duty. Hotels and motels should consider that

employees with appropriate pool and spa operation training

are needed on weekends, when usage is typically highest.

Enhanced monitoring and maintenance should be implemented when a large group or event at a hotel is scheduled.

Multiple aquatic facilities have transitioned to employing remote monitoring services to check pool chemistry (e.g.,

chlorine and pH) on a regular basis and to alert the facility

of any problems that arise. Breakdowns in communication

between these remote monitoring services and the aquatic

facility seem to facilitate problems that occur for long periods, without correction, which was documented in a large

outbreak of Pseudomonas dermatitis in Illinois (January

2003) and several previous outbreaks (30). Facilities should

not rely on off-site monitoring companies as the sole overseers of their aquatic facilities. Although remote monitoring can be beneficial in detecting water-quality problems,

the service should not take the place of routine waterquality checks, which are required in the majority of pool

codes. To prevent adverse events, having 1) clear communication plans for relaying warnings concerning problems,

2) prompt alerts so corrections can be made, and 3) diligent staff who immediately respond to alerts are essential.

To prevent spa-associated outbreaks, understanding the

risk factors and steps that can be taken is necessary to limit

transmission of the bacteria. Proper chlorination or bromination is effective in killing Pseudomonas and other skininfecting bacteria. However, sufficient chlorine and bromine

levels must be maintained consistently along with adequate

pH control to limit bacterial amplification. Poor maintenance of spas has been documented (31). Cycling between

high and low disinfectant levels allows biofilms to proliferate on spa surfaces, creating an environment where Pseudomonas and other bacteria are protected from disinfection (32).

A review of 18 Pseudomonas outbreaks has demonstrated

that all spa-associated outbreaks had inadequate disinfection (33). The majority of Pseudomonas outbreaks can be

prevented by properly maintaining spas and by ensuring

that disinfectant levels remain >1 ppm and pH levels

remain in a range of 7.2–7.8. In addition, elimination of

potential sources of Pseudomonas (e.g., soil from potted

plants in close proximity to the water) (Illinois, January

2003) is advisable.

Pseudomonas is not the only bacterium that can cause

spa-related skin infections. MRSA was associated with an

outbreak involving an athletic spa in Connecticut (August

2003; 34). MRSA infections can have substantial consequences, as in this outbreak in which otherwise healthy

young athletes were hospitalized. Factors contributing to

this outbreak included the presence of skin abrasions on

the athletes from “turf burns” and body shaving, and the

communal use of an athletic spa that employed limited

and unproven disinfection methods. Appropriate spa

operation, maintenance, and cleaning should prevent outbreaks of this emerging infectious disease.

Legionellosis

Legionellae, which cause both Legionnaires’ disease and

PF, are ubiquitous in freshwater environments (35). However, certain environmental conditions in spas (e.g., high

temperatures and water aerosolization) promote the

amplification and transmission of the bacteria. Similar to

outbreaks of Pseudomonas dermatitis associated with spas,
Vol. 55 / SS-12 Surveillance Summaries 19

transmission of Legionella is more likely to occur in the

absence of adequate levels of disinfectant, underscoring the

importance of maintaining disinfectant levels and pH control. When lapses in preventive measures occur and

Legionella outbreaks occur, morbidity can be reduced by

rapid recognition of the outbreak, identification of its

source, and immediate implementation of remediation.

These methods include cleaning and disinfecting the spa

to eliminate Legionella colonization and performing followup cultures of Legionella to ensure that regrowth does not

occur (36). Of the four Legionella WBDOs associated with

recreational water during 2003–2004 (as well as one from

2002 which was previously unreported), all except one were

associated with hotel spas. These travel-associated WBDOs

highlight the importance of timely reporting of individual

cases of legionellosis, which was recently recommended in

a 2005 CSTE position statement (http://www.cste.org/PS/

2005pdf/final2005/05-ID-01final.pdf).

Interactive Fountains/Wet Decks

and Waterslides

Infectious Gastroenteritis

Certain treated water venues (e.g., interactive fountains,

which are also called wet decks) might be overlooked as

potential sites for disease transmission or pool regulation

because they do not have the standing water found in traditional swimming pools. Outbreaks in this report continue to demonstrate the possibility of infection occurring

in these settings. The use of interactive fountains has previously been associated with outbreaks of gastroenteritis (37).

In two WBDOs in this report, contaminated interactive

fountains are implicated; one involved a S. sonnei–contaminated fountain (Oregon, July 2003), and the other involved

a Cryptosporidium-contaminated (Illinois, July 2004) fountain and swimming pool. In certain states, interactive fountains are not regulated as other recreational water venues,

and fountain designs that include recirculation of the bathing water make these venues vulnerable to contamination.

New designs that improve water treatment for these interactive fountains are needed so that visitors can enjoy them

without risk from waterborne diseases.

The traditional use of tap water to fill or operate temporary aquatic venues (e.g., wading pools and waterslides) used

by young children also needs to be reconsidered, particularly in institutional settings (e.g., day care centers and

schools). If the water is not treated with adequate levels of

disinfectant, residual disinfectant in the water is rapidly

depleted; users are then at higher risk of exposure to infectious microbes in the untreated water. Special consideration needs to be given to kiddie pools, some of which have

had unfavorable water-quality test results and associations

with previous outbreaks (38). In one Cryptosporidium outbreak (Iowa, June 2003), a kiddie pool at a day care facility

was filled with potable municipal water that had not

received additional treatment, expediting infection of children and eventual expansion into a communitywide outbreak. In Kansas (July 2003), the communitywide outbreak

also involved use of kiddie wading pools and in-ground

pools at local day care centers. Portable waterslides in which

municipal water is used also might be overlooked as sources

of disease transmission because they can be set up, used,

and taken down in a matter of hours. The outbreak in

Florida associated with a waterslide (May 2004) demonstrated that the use of these slides by a person infected

with a fecal-oral transmissible microbe (in this case,

norovirus) contaminated the waterslide, so it became an

ideal venue for spreading disease. As with pools, spas, and

fountains, appropriate treatment of recreational water venues and exclusion of persons with diarrhea is needed to

prevent disease transmission. Furthermore, the use of temporary pools filled with municipal water that do not

include routine disinfection and filtration should be considered carefully by the public and, based on documented

outbreaks, should be eliminated from institutional settings

(e.g., day care centers and schools).

Lakes and Rivers

Infectious Gastroenteritis

Since the WBDOSS began collecting data on recreational

water outbreaks, reports have implicated both treated and

untreated venues. Since 1998, the numbers of reported outbreaks from treated water venues have surpassed those from

untreated venues (Figure 11). For 2003–2004, a total of

12 outbreaks of gastroenteritis associated with untreated

freshwater venues were reported; 11 of these outbreaks

involved lakes, and one involved a reservoir. Freshwater outbreaks were more likely to be of a bacterial or viral origin

than treated water outbreaks (Figure 5).

As with treated venues, human behavior plays a role in

the spread of pathogens in untreated bodies of water. For

example, in an outbreak in Maryland (July 2003), 5–10

diapers were reportedly retrieved from the lake each week.

Modification of swimmer behavior might be a more critical factor because these natural water venues do not have

the benefit of disinfection and filtration barriers. Recommendations for swimmer hygiene are the same for lakes, as
20 MMWR December 22, 2006

previously discussed regarding treated pools. In addition,

beach managers and swimmers should be informed that

shallow swimming areas with poor water circulation,

although desirable to many swimmers, might pose a higher

risk if a swimmer contaminates the water. Use of methods

to improve circulation of water through these beach areas

should be explored for the potential to reduce the risk for

waterborne disease transmission. Additional reduction of risk

might be accomplished by avoiding swimming immediately

after a heavy rainfall when the water is at higher risk for

transient contamination, and by avoiding swimming near

storm drains or pipes that might release sewage into bodies

of water. The use of water-quality monitoring (e.g., fecal indicator testing) by beach managers might also reduce risk

(15), particularly when more rapid testing methods are

implemented by EPA (16).

Primary Amebic Meningoencephalitis

Whereas infection with Naegleria fowleri, the cause of

primary meningoencephalitis (PAM), is a rare occurrence

in the United States (39), this disease has public health

importance because of its high fatality rate. This free-living

ameba proliferates in warm freshwater and hot springs. PAM

is caused when the ameba coincidentally enters the nasal

passages, travels to the olfactory lobe of the brain, and

infects brain tissue. Only one fatality (North Carolina, July

2003) was reported for this 2003–2004 surveillance cycle

(excluding Vibrio illnesses). During the summer, a young

child was exposed to infection through warm lake water,

similar to cases of PAM during previous years. PAM is difficult to predict, and prevention strategies might not prevent these tragic events. However, swimmers potentially

can reduce their risk of PAM by wearing nose plugs, holding their nose while diving or jumping into the water,

refraining from digging in sediment, and avoiding swimming in shallow waters during the warmest times of the

year. Additional resources are needed to develop more evidence-based prevention measures.

Leptospirosis

Leptospirosis infection occurs worldwide, except in

polar regions, and particularly in tropical and semitropical

areas of the world, including several of the Pacific islands

that report to this surveillance system (40). Leptospira can

be found in the urine of infected wild and domesticated

animals. Human infection can occur when contaminated

water is ingested, aerosolized droplets are inhaled, or water

enters the body through skin abrasions. One outbreak of

leptospirosis was reported for 2003–2004 and involved

three cases, which resulted from exposure to a river and

waterfalls in Guam (April 2004). This outbreak occurred

among U.S. military personnel in a remote area, and water

buffalo moving through that region were suspected to have

been the possible sources of contamination.

Blue-Green Algae Toxicity

Toxin or chemical-associated outbreaks can occur by natural mechanisms. Blue-green algae that bloom in freshwater

lakes have been identified as sources of outbreaks of human

waterborne diseases in multiple countries (41). The toxins

involved include anatoxin (i.e., a potent neurotoxin) and

microcystins (i.e., potent liver toxins), and poisonings can

cause various symptoms. These symptoms were observed

in two outbreaks (Nebraska, 2004) in which 22 persons

became ill with ARI and dermatologic symptoms. The

actual number of persons who become ill after exposure to

blue-green algal toxins in drinking and recreational waters

is not known; substantial research is needed to identify the

actual extent of this public health threat. Toxin levels can

be measured in samples collected from lakes where blooms

occur. Currently no regulations exist that establish acceptable toxin levels in drinking or recreational water.

Cercarial Dermatitis

During the 2003–2004 surveillance period, two WBDOs

of suspected cercarial dermatitis caused by avian schistosomes were reported (California, June 2003; Ohio, June

2003). Although the diagnosis was not confirmed, this selflimited disease is known to occur in lakes across America

where the intermediate host snail species are found and a

population of suitable bird hosts are present (42). Cases of

cercarial dermatitis might be reduced by posting warning

signs at lakes known to be infested, avoiding shallow swimming areas where infected snails reside, instituting a snailcontrol program, and by not attracting birds to swimming

areas (e.g., by feeding them).

FIGURE 11. Number of recreational water associated outbreaks

of gastroenteritis (n = 206), by water type and year — United

States, 1978–2004

0

4

8

12

16

1978 1982 1986 1990 1994 1998 2002

Year

No. of outbreaks

Treated

Untreated
Vol. 55 / SS-12 Surveillance Summaries 21

Marine Water

Vibrio Illness

A limited number of outbreaks at marine venues have

been reported to the WBDOSS. Outbreaks in these settings can be difficult to detect because persons affected frequently travel from distant locations to visit these venues

and might disperse before a health problem is recognized.

However, single cases of Vibrio infections from recreational

water exposure are captured through the Cholera and Other

Vibrio Illness Surveillance System (http://www.cdc.gov/

foodborneoutbreaks/vibrio_sum/cstevibrio2004.pdf) and

represent an essential aspect of waterborne morbidity and

mortality in the United States. As a result, recreational

water-associated Vibrio illnesses will now be included in

the WBDOSS to report the scope of waterborne disease in

the United States in a more comprehensive manner.

During 2003–2004, the most commonly reported species were V. vulnificus, V. alginolyticus, and V. parahaemolyticus.

Of these species, V. vulnificus illnesses had the highest hospitalization rate (87.2%) and mortality rate (i.e., 12.8%

of infected patients with recreational water exposure). The

predominant syndrome associated with Vibrio illness caused

by recreational water was wound infection. Vibrio wound

infections were characterized by cellulitis, muscle pain, and

especially with V. vulnificus, bullae, and septicemia.

Vibrio illness caused by recreational water exposures

occurs in all regions of the United States but most frequently

occur along the Gulf Coast. However, the majority of

V. alginolyticus cases occur in the Pacific coast states, where

the most common exposures occur through surfing and

swimming. Improved surveillance and analysis is needed

to 1) assess the actual magnitude of Vibrio illness and other

WBDOs at marine water venues, 2) better characterize the

risk, and 3) educate the public concerning appropriate prevention measures (e.g., not swimming in warm water when

a person has an open wound).

Prevention

Prevention of recreational water illnesses is likely to be

accomplished only through a concerted team effort by public health professionals and swimming venue operators to

educate all persons involved in recreational water activities,

including the general public, concerning appropriate prevention measures. Operators at treated water venues are

equipped with various methods that should be employed

to prevent outbreaks. The traditional reliance on two watertreatment barriers at treated water venues, chlorination and

filtration, might need to be expanded to include in-line

(i.e., usually installed after filtration and before chlorination) supplemental disinfection (e.g., ultraviolet light irradiation, ozonation, or chlorine dioxide use). In-line

supplemental disinfection can be used to improve the level

of protection against pathogens, particularly Cryptosporidium. Improved monitoring of water-quality and facility maintenance programs and improved policies to educate

the public and decrease body waste contamination of aquatic

facilities should also reduce the risk for waterborne diseases. Because of the lack of protective barriers at swimming beaches, beach managers and public health

officials should implement water-quality testing programs

and educate swimmers concerning appropriate prevention

measures, particularly measures addressing environmental

pathogens unlikely to be prevented by current waterquality 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, and 3) lead the

educational efforts with aquatic staff and the general public. Safe handling and use of chemicals at aquatic facilities

needs to be taught and reinforced. In addition, to improve

overall indoor air quality, public health professionals and

pool managers need to understand the importance of

indoor air quality so that improvements in pool water quality, swimmer hygiene, air-turnover rates, and ventilation

will be implemented.

Educating swimmers can play a vital role in reducing

recreational water illness by instructing them to follow basic

guidelines for healthy swimming. Fecal shedding of pathogens is common (43), so reducing the risk of water-related

infection is best achieved by implementing diarrhea exclusion policies, using appropriate hygiene measures, and

advising the public to minimize the swallowing of recreational water.

Conclusion

Data collected by the WBDOSS are used to characterize

the epidemiology of waterborne disease and outbreaks

associated with both drinking and recreational water. Swimming is a common activity in the United States (44). Certain disease-causing agents are spread through shared bodies

of water, and new waterborne pathogens that infect

humans (e.g., Cryptosporidium and toxigenic E. coli) have

emerged in the previous three decades. Recreational water

illness and outbreaks are associated with both treated and
22 MMWR December 22, 2006

untreated water and with every type of aquatic venue. Common themes derived from the outbreaks in this report

include 1) low disinfectant levels, 2) inadequate waterquality monitoring, 3) high bather loads during large events,

4) breakdowns of equipment and lengthy detection times,

5) lack of essential cleaning of spas to minimize biofilm

buildup, 6) accumulation of combined chlorines in pools

accompanied by inadequate indoor air ventilation, 7)

inadequately trained aquatic staff, 8) unclear communication chains for resolving problems, 9) outbreaks occurring

on weekends when trained staff might be off duty, and 10)

a lack of awareness by the general public of appropriate

healthy swimming behaviors.

Whereas no easy solution exists for reducing recreational

water WBDOs, a sustained effort by the swimming public, the pool 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 informed regarding 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 both safe and 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

pool codes occur each year (14,31), indicating that

improved pool operation, disinfection policies, and enforcement are needed to prevent recreational water illness (45).

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.

Public health professionals at all levels of government

should lead a multidisciplinary approach to prevent recreational water illness that includes 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 levels 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 of recreational water illness, 2) facilitate reporting to the

WBDOSS in a more timely manner, and 3) strengthen

WBDO investigations and responses to protect the public.

The timely collection of clinical specimens and water samples

for testing during a WBDO investigation and the initiation of an environmental investigation will result in more

rapid identifications 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 a variety of disciplines, including infectious disease epidemiology, environmental health, clinical medicine, water and sanitation

engineering, and microbiology. Additional cross-training

of existing personnel in these areas or additional staffing

and resources are needed to improve WBDO detection,

investigation, and reporting.

CSTE passed a position statement at its 2006 annual

meeting making waterborne disease outbreaks, as a unit of

reporting, 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 waterborne outbreaks at the

state and local levels. CDC and EPA were also asked to

develop training resources for WBDO investigations that

are targeted to local and state/territorial public and environmental health workers responsible for WBDO detection, investigation, and reporting. In addition, CDC and

EPA should collaborate with CSTE and developed national

WBDO investigation and surveillance guidelines. The

position statement is available at http://www.cste.org/PS/

2006pdfs/PSFINAL2006/06-ID-12FINAL.pdf (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, John Williamson, PhD, Division of Parasitic Diseases, National

Center for Zoonotic, Vector-Borne, and Enteric Diseases (proposed),

CDC; Lorraine Backer, PhD, Division of Environmental Hazards and

Health Effects, National Center for Environmental Health, CDC;

Charles Otto, Division of Emergency and Environmental Health

Services, National Center for Environmental Health, CDC;

Mohammed Siddiqui, New York State Department of Health, Troy,

New York.

References

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

FL: CRC Press, Inc.; 1986.

2. Yoder JS, Blackburn BG, Craun GF, et al. Surveillance for recreational

water-associated outbreaks—United States, 2001–2002. In: Surveillance

Summaries, October 22, 2004. MMWR 2004;53(No. SS-8):1–21.
Vol. 55 / SS-12 Surveillance Summaries 23

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

recreational water exposure

State health departments can request epidemiologic

assistance and laboratory testing from CDC to investigate WBDOs. CDC and the U.S. Environmental Protection Agency (EPA) can be consulted regarding

engineering and environmental aspects of recreational

water treatment and collection of proper water samples

to identify pathogenic viruses, bacteria, and parasites,

which require special protocols for their recovery.

National WBDO Investigation and Surveillance

Guidelines

CDC, EPA, and CSTE Position Statement

Internet: http://www.cste.org/PS/2006pdfs/PS

FINAL2006/06-ID-12FINAL.pdf

How to Report WBDOs

Waterborne Disease Outbreak Coordinator

Division of Parasitic Diseases

National Center for Zoonotic, Vector-Borne, and

Enteric Diseases (proposed)

Coordinating Center for Infectious Diseases, CDC

Telephone: 770-488-7775

Fax: 770-488-7761

CDC Reporting Form (CDC 52.12, rev.01/2003)

Internet: http://www.cdc.gov/healthyswimming/

downloads/cdc_5212_waterborne.pdf

Requests for Testing for Viral Organisms

Division of Viral Diseases

National Center for Immunization and Respiratory

Diseases (proposed)

Coordinating Center for Infectious Diseases, CDC

Telephone: 404-639-3607

Requests for Testing for Bacterial Enteric Organisms

Division of Foodborne, Bacterial, and Mycotic

Diseases

National Center for Zoonotic, Vector-Borne, and

Enteric Diseases (proposed)

Coordinating Center for Infectious Diseases, CDC

Telephone: 404-639-1798

Requests for Testing for Parasites

Division of Parasitic Diseases

National Center for Zoonotic, Vector-borne, and

Enteric Diseases (proposed)

Coordinating Center for Infectious Diseases, CDC

Telephone: 770-488-7775

Requests for Information or Testing for Legionella

Division of Bacterial Diseases

National Center for Immunization and Respiratory

Diseases (proposed)

Coordinating Center for Infectious Diseases, CDC

Telephone: 404-639-2215

Internet: http://www.cdc.gov/legionella

Information Regarding Legionellosis

Internet: http://www.cdc.gov/legionella

CDC provides public health professionals, clinicians,

laboratorians, and persons in other allied health fields

with background and clinical information, guidance on

investigations, and resources concerning Legionnaires’

disease and Pontiac fever cases or potential outbreaks.

Resources include outbreak investigative tools, environmental sampling protocols, fact sheets, clinical evaluation and management guides, and laboratory testing

protocols.

Information Regarding Healthy Swimming

CDC Internet: http://www.cdc.gov/healthyswimming

• Recreational water health communication and education resources for the general public and aquatic

staff

• Pool and spa operation guidelines, including disinfection and fecal accident response

• Outbreak investigation toolkit and technical information concerning laboratory diagnostics

Information Regarding Beaches

EPA Internet: http://www.epa.gov/OST/beaches

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.
24 MMWR December 22, 2006

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

Surveillance for waterborne-disease outbreaks—United States, 1993–

1994. In: CDC Surveillance Summaries, April 12, 1996. MMWR

1996;45(No. SS-1):1–33.

8. Moore AC, Herwaldt BL, Craun GF, Calderon RL, Highsmith AK,

Juranek DD. Surveillance for waterborne disease outbreaks—United

States, 1991–1992. In: CDC Surveillance Summaries, November 19,

1993. MMWR 1993;42(No. SS-5):1–22.

9. Herwaldt BL, Craun GF, Stokes SL, Juranek DD. Waterborne-disease

outbreaks, 1989–1990. In: CDC Surveillance Summaries, December

1991. MMWR 1991;40(No. SS-3):1–21.

10. Levine WC, Stephenson WT, Craun GF. Waterborne disease outbreaks, 1986–1988. In: CDC Surveillance Summaries, March 1, 1990.

MMWR 1990;39(No. SS-1):1–9.

11. St. Louis ME. Water-related disease outbreaks, 1985. In: CDC Surveillance Summaries, June 1, 1988. MMWR 1988;37(No. SS-2):15–24.

12. 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.

13. Chastel C. When the Egyptian mummies are speaking about the infections that have made them ill. Hist Sci Med 2004;38:147–55.

14. CDC. Surveillance data from swimming pool inspections—selected

states and counties, United States, May–September 2002. MMWR

2003;52:513–6.

15. Environmental Protection Agency. Bacterial ambient water quality

criteria for marine and fresh recreational waters. Cincinnati, OH:

National Service Center for Environmental Publications; 1986. EPA

publication no. 440584002.

16. Wade TJ, Calderon RL, Sams E, et al. Rapidly measured indicators of

recreational water quality are predictive of swimming-associated gastrointestinal illness. Environ Health Perspect 2006;114:24–8.

17. Rao PV, Gupta N, Bhaskar AS, Jayaraj R. Toxins and bioactive compounds from cyanobacteria and their implications on human health.

J Environ Biol 2002;23:215–24.

18. Hery M, Hecht G, Gerber JM, Gendre JC, Hubert G, Rebuffaud J.

Exposure to chloramines in the atmosphere of indoor swimming pools.

Annals of Occupational Hygiene 1995;39:427–39.

19. Emanuel BP. The relationship between pool water quality and ventilation. Environmental Health 1998;61:17–20.

20. Massin N, Bohadana AB, Wild P, Hery M, Toamain JP, Hubert G.

Respiratory symptoms and bronchial responsiveness in lifeguards

exposed to nitrogen trichloride in indoor swimming pools. Occup

Environ Med 1998;55:258–63.

21. Pruss A. Review of epidemiological studies on health effects from exposure to recreational water. International J Epidemiol 1998;27:1–9.

22. Korich DG, Mead JR, Madore MS, Sinclair NA, Sterling CR. Effects

of ozone, chlorine dioxide, chlorine, and monochloramine on

Cryptosporidium parvum oocyst viability. Appl Environ Microbiol

1990;56:1423–8.

23. Mohle-Boetani JC, Stapleton M, Finger R, et al. Communitywide

shigellosis: control of an outbreak and risk factors in child day-care

centers. Am J Public Health 1995;85:812–6.

24. CDC. An outbreak of norovirus gastroenteritis at a swimming club—

Vermont, 2004. MMWR 2004;53:793–5.

25. CDC. Aseptic meningitis outbreak associated with echovirus 9 among

recreational vehicle campers—Connecticut, 2003. MMWR 2004;

53:710–3.

26. Lagerkvist BJ, Bernard A, Blomberg A, et al. Pulmonary epithelial

integrity in children: relationship to ambient ozone exposure and swimming pool attendance. Environ Health Perspect 2004;112:1768–71.

27. 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.

28. Clancy JL, Marshall MM, Hargy TH, Korich DG. Susceptibility of

five strains of Cryptosporidium parvum oocysts to UV light. Journal

AWWA 2004;96:84–93.

29. Berger RS, Seifert MR. Whirlpool folliculitis: a review of its cause,

treatment, and prevention. Cutis 1990;45:97–8.

30. CDC. Pseudomonas dermatitis/folliculitis associated with pools and hot

tubs—Colorado and Maine, 1999–2000. MMWR 2000;49:1087–91.

31. CDC. Surveillance data from public spa inspections—United States,

May–September 2002. MMWR 2004;53:553–5.

32. Donlan RM. Biofilms: microbial life on surfaces. Emerg Infect Dis

2002;8:881–90.

33. Gustafson TL, Band JD, Hutcheson RH Jr, Schaffner W. Pseudomonas

folliculitis: an outbreak and review. Rev Infect Dis 1983;5:1–8.

34. Begier EM, Frenette K, Barrett NL, et al. A high-morbidity outbreak

of methicillin-resistant Staphylococcus aureus among players on a college football team, facilitated by cosmetic body shaving and turf burns.

Clin Infect Dis 2004;39:1446–53.

35. Fields BS, Benson RF, Besser RE. Legionella and Legionnaires’ disease:

25 years of investigation. Clin Microbiol Rev 2002;15:506–26.

36. 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.

37. CDC. Outbreak of gastroenteritis associated with an interactive

water fountain at a beachside park—Florida, 1999. MMWR

2000;49:565–8.

38. CDC. Shigellosis outbreak associated with an unchlorinated fill-anddrain wading pool—Iowa, 2001. MMWR 2001;50:797–800.

39. Visvesvara GS, Stehr-Green JK. Epidemiology of free-living ameba

infections. J Protozool 1990;37:25S–33S.

40. Bharti AR, Nally JE, Ricaldi JN, et al. Leptospirosis: a zoonotic disease of global importance. Lancet Infect Dis 2003;3:757–71.

41. Zurawell RW, Chen H, Burke JM, Prepas EE. Hepatotoxic

cyanobacteria: a review of the biological importance of microcystins in

freshwater environments. J Toxicol Environ Health B Crit Rev

2005;8:1–37.

42. Verbrugge LM, Rainey JJ, Reimink RL, Blankespoor HD. Swimmer’s

itch: incidence and risk factors. Am J Public Health 2004;94:738–41.

43. Gerba CP. Assessment of enteric pathogen shedding by bathers during

recreational activity and its impact on water quality. Quant Micrbiol

2000;2:55–68.

44. US Bureau of the Census. Statistical abstract of the United States:

1995. 115th ed. Washington, DC: US Bureau of the Census; 1995.

45. CDC. Responding to fecal accidents in disinfected swimming venues.

MMWR 2001;50:416–7.
Vol. 55 / SS-12 Surveillance Summaries 25

Appendix A

Glossary of Definitions

bather load The maximum number of bathers who may use a swimming pool or spa at any one time.

This limit is usually determined by 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/skin perforation by the cercariae (larval stage) of certain

species of schistosomes, a type of parasite, for which the normal hosts are birds and

nonhuman mammals. This allergic response 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 water-quality data implicating recreational water as the source of the disease or

outbreak (see Table 1).

chloramines A group of disinfection by-products or weak disinfectants formed when free chlorine combines with nitrogen-containing compounds in the water (e.g., urine or perspiration). Triand di-chloramine can cause eye, skin, lung, and throat irritation and can accumulate in

the water and air over treated-water pools. In drinking water treatment, monochloramine

is used for disinfection to reduce formation of disinfection by-products created when

using chlorine as a disinfectant.

coliforms All aerobic and facultative anaerobic, gram-negative, nonspore-forming, rod-shaped bacteria that ferment lactose with gas formation within 48 hours at 95o

F (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.

contact time The length of time water (and pathogens) is exposed to a disinfectant; usually measured in

minutes (e.g., chlorine contact time).

Cryptosporidium The taxonomy of Cryptosporidium has evolved as a result of advancements in molecular

methodology and genotyping. The former C. parvum now refers to a species that is zoonotic

and infects ruminants and humans. C. hominis refers to the species of Cryptosporidium that

is infective only in humans, primates, and monkeys. Both species were referred to previously as C. parvum.

dermatitis Inflammation 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.

etiologic agent The pathogen, chemical, or toxin causing a waterborne disease or outbreak. Infectious

etiologic agents include bacteria, parasites, and viruses.
26 MMWR December 22, 2006

fecal coliforms Coliforms that grow and ferment lactose to produce gas at 112.1oF (44.5oC) within 24 hours.

filtration The process of removing suspended particles from water by passing it through one or more

permeable 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).

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 feature 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 on

humans 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 Cryptosporidium species 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.

predominant illness The category of symptoms most commonly expressed in a substantial proportion (>50%)

of patients (e.g., gastroenteritis, dermatitis, acute respiratory illness). When more than

one illness category 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 waterparks)

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 may be available for recreational use.

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. Sometimes referred to as a hot tub or

whirlpool.
Vol. 55 / SS-12 Surveillance Summaries 27

total chlorine The chlorine in water that is free for disinfection (free chlorine) plus that combined with other

organic materials (combined chlorine). A common water quality test. 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 may 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.

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

Vibrio species A genus of comma-shaped, gram-negative Proteobacteria that include a variety of human

pathogens. Some of these 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.

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).
28 MMWR December 22, 2006

Appendix B

Selected Descriptions of Waterborne Disease and Outbreaks (WBDOs)

Associated with Recreational Water

No. of

Date of State in which cases

WBDO WBDO occurred Etiologic agent (deaths) Description of WBDO

Parasites

June 2003 Massachusetts Giardia intestinalis 149 A community outbreak of giardiasis was traced to a membership club. The investigation

demonstrated an association with use of a kiddie pool at the facility, where at least 30 persons

had primary exposures. Another 105 cases had links to those primary cases, indicating

secondary person-to-person transmission. No violations of water or safety regulations were found

by inspection of the membership club, although the pool closed for the season before the

investigation was conducted.

June 2003 Iowa Cryptosporidium 63 A kiddie wading pool at a child care center, filled with the municipal water supply, was

and Giardia spp. implicated as the original source of this outbreak. This was followed by expansion into a

communitywide outbreak via secondary transmission. An estimated 100 persons became ill,

although the reported number of confirmed cases was 63; 20 persons had Giardia, 35 had

Cryptosporidium, and eight had coinfections.

July 2003 Kansas C. hominis 617 An increased incidence of laboratory-confirmed cryptosporidiosis alerted a local health department, and the subsequent inquiry revealed an ongoing communitywide outbreak with multiple

clusters identified. Although the initial point of transmission could not be identified, transmission

was associated with swimming pools (different swim teams, day camps), and multiple day care

facilities where water activities were prevalent. Children who continued to swim while ill with

diarrhea likely contributed to the continued spread of disease.

July 2003 North Carolina Naegleria fowleri 1 (1) A child aged 12 years swam at a popular recreational freshwater lake with frequent splashing,

diving, and swimming underwater giving ample opportunity for the ameba to enter the nasal

cavities. The child had a headache 2 days later, was hospitalized 4 days after the headache, and

died 3 days later.

July 2004 Ohio C. hominis 160 A health-care professional alerted the health department about a cluster of cryptosporidiosis

cases. The health department responded rapidly through community health alerts,

hyperchlorination of the community pool, and expanded public health activity at a county festival.

An estimated 85% of patients swam at a community pool in the 2 weeks leading up to their onset

of illness. Two peak days of attendance in August 2004 were identified as the likely time of

exposure for the majority of cases, which was only 1 week before the initial health department

response. Although ill persons resided in three different Ohio counties, the investigation indicated

a low rate of transmission in any of the affected counties and that little transmission occurred

beyond the municipal pool. Hyperchlorination of the pool appeared to be effective in stopping

transmission, and a rapid response and containment of the outbreak were likely responsible for

preventing further spread.

August 2004 California Cryptosporidium spp. 336 A recreational waterpark was implicated as the source of this outbreak. Approximately 80% of

persons calling the county health department to report illness had visited the park before their

onset of symptoms. Many of the employees of the waterpark were ill with a median onset date

that preceded that for ill members of the public. Park policy required employees to be in the water

regularly, and no policy was in place for reassigning employees who were ill with diarrhea.

Bacteria

December 2002 Florida Legionella pneumophila 2 Two non-Florida residents had Legionnaires’ disease and were epidemiologically linked to a Florida

serogroup 1 hotel at which they had both stayed during their incubation periods. In addition, the spa was the

only common location identified at the hotel in which transmission could have occurred. Both

patients had spent several hours each day in the spa. Though no Legionella species were

recovered from the spa, the levels of bromine disinfectant were low and resulted in an environment where the pathogen was more likely to grow.

January 2003 Illinois Pseudomonas 52 Multiple guests of a large hotel contracted dermatitis and/or ear infections and an investigation

aeruginosa associated spa usage with illness. Records from an off-site monitoring company demonstrated

that chlorine (oxidation reduction potential was actually measured) and pH levels were well below

recommended levels. Communication between the monitoring company and hotel did not result in

prompt maintenance of the spa. The hotel eventually discovered that the chlorinator pump switch

had been turned off. A potted plant and soil near the spa might have contributed to contamination, and Pseudomonas was detected in multiple environmental samples from the spa.

February 2003 Wisconsin L. pneumophila 3 Three cases of Legionnaires’ disease were linked to a hotel spa. Legionella was isolated from the

serogroup 1 spa water that had insufficient disinfectant concentrations. Active case-finding also identified

persons with potential signs and symptoms of Pontiac fever, each of whom was exposed to the

implicated spa.
Vol. 55 / SS-12 Surveillance Summaries 29

May 2003 Georgia Shigella sonnei 13 Contact with or having water from a freshwater lake in the mouth was associated with increased

risk for shigellosis. Attack rates ranged from 38%–58% and increased with prolonged exposure.

Fecal coliform measurements exceeded recommended standards. The man-made lake had no

outlets, and septic systems were adequate. Investigators concluded that contamination was likely

caused by fellow bathers.

July 2003 Maryland S. sonnei and 65 Visitors from four different states swam in a state park lake and became ill with gastroenteritis.

Plesiomonas Fecal coliform and Escherichia coli levels exceeded standards on at least one sample collection

shigelloides time. Lifeguards at the lake reported that 5–10 diapers were pulled from the lake each week, and

on one occasion, a camper was observed dumping waste into a drain that flowed into the lake

instead of into the dump station. Both behaviors were suggested as contributing to contamination

of the lake. The bathing beach permit was temporarily suspended during the investigation and

partially obstructed sewer lines repaired.

July 2003 Oregon S. sonnei 56 After a physician reported seeing five unrelated children with diarrhea, an investigation linked

transmission to a local interactive fountain commonly visited by community children. A casecontrol study indicated that 39% of children who played in the fountain subsequently experienced

diarrhea, compared with 3% of those who did not visit the fountain. Fecal coliforms and E. coli

were detected in the water, and zero chlorine residual could be measured. This particular fountain

was subsequently redesigned to include an automated chlorinator and was required to be licensed

and regulated as a public wading pool.

August 2003 Connecticut Methicillin-resistant 10 In an investigation of a MRSA outbreak within a college football team of 100 players, 10 cases

Staphylococcus aureus were detected, two needing hospitalization. Risk factors included abrasions from artificial grass

(“turf burns”), player positions with more frequent body-to-body contact (cornerbacks and wide

receivers), and body shaving (particularly groin/genital shaving). Infection also was associated

with sharing the whirlpool spa at the team’s athletic training center. The water in this spa used a

single daily addition of povidone for disinfection. This practice of adding disinfectant did not meet

Connecticut pool code regulations nor was the disinfectant approved for this use.

March 2004 Oklahoma L. pneumophila 107 A hotel hosted participants of a youth basketball tournament over several days. Many of the

serogroup 1 guests were using the hotel spa throughout this period, leading to occasional bather overload.

Disinfectant levels in the water were not being consistently monitored or maintained during this

time. Four cases required hospitalization; however, the majority of ill persons had symptoms of

Pontiac fever. Urine antigen testing and serology were used for laboratory confirmation.

Environmental testing of the spa and its surroundings, which was performed after extensive

decontamination measures took place, did not reveal evidence of Legionella growth.

July 2004 Ohio P. aeruginosa 119 Two pools and a spa at a resort hosting an interstate dance competition were all associated with

this large Pseudomonas outbreak. Symptoms included rash, eye and ear infections, fever,

nausea, vomiting, and diarrhea. The water from an indoor pool and the spa could co-mingle

because of specific design features (e.g., waterfalls) connecting the features, and water samples

from both were positive for the Pseudomonas. This contamination, along with the high bather load

resulting from the dance competition, provided the opportunity for widespread transmission.

Viruses

July 2003 Connecticut Echovirus 9 36 An outbreak of meningitis was associated with swimming at an RV campground pool. The

investigation identified 36 cases; 12 of which were categorized as aseptic meningitis and 24 that

had enterovirus-like illness (acute illness with any of several meningitis-like symptoms). Pool

disinfectant levels were inadequate to support a high bather load. Chlorine testing was only

performed in the early morning and evening after heavy bather use.

February 2004 Vermont Norovirus 70 The state health department was notified of a group of children with gastroenteritis who had all

attended the same swimming club during the previous weekend. The investigation revealed

several more cases, including an adult who was hospitalized for severe vomiting. Multiple lapses

in pool staff training and maintenance contributed to the outbreak. Staff lacked formal training in

pool operation, disinfectant levels and monitoring were inadequate, the pool operator was off for

the weekend, and the pool staff did not call for maintenance when patrons complained about the

water quality. This led to a delay in identifying a chlorinator pump tube malfunction. As a result,

norovirus was transmitted via the pool water for much longer (multiple days) than would have

occurred if disinfectant levels were appropriately maintained.

March 2004 Idaho Norovirus 140 A regional swim meet at a community pool facility was associated with this outbreak of

gastroenteritis. Although cases occurred amongst swimmers (approximately 450) and nonswimmers (approximately 550) at the event, swimming in the pools was a significant risk factor. Certain

proper hygiene measures, such as showering before entering the pool and having functional hand

washing sinks in the restrooms, were not being consistently followed and could have amplified

spread of the disease. Both pools were found to be within normal operating limits for free chlorine

(1.0–3.0 ppm) and pH (7.2–7.8) before and during the meet, although this would be unlikely to

prevent short-term transmission.

May 2004 Florida Norovirus 42 An elementary school “game day” included two water slides that were wet down with municipal tap

water so that the water was likely to be disinfectant free in a short period. After one of the slides

was used by a child with diarrhea, several classmates continued to use the slide, as students

from another class did while the original class ate lunch. Students from both classes, as well as

household contacts, became ill.

No. of

Date of State in which cases

WBDO WBDO occurred Etiologic agent (deaths) Description of WBDO
30 MMWR December 22, 2006

July 2004 Oregon Norovirus 39 Swimming beaches at a lake were closed after initial reports of several cases of gastroenteritis

were received. This popular recreational lake had been receiving routine bacterial water quality

testing since 1991, when it was the site of a 59-case outbreak of E. coli O157:H7 and Shigella

sonnei (Source: Keene WE, McAnulty JM, Hoesly FC, Williams LP Jr, Hedberg K, Oxman GL,

Barrett TJ, Pfaller MA, Fleming DW. A swimming-associated outbreak of hemorrhagic colitis

caused by Escherichia coli O157:H7 and Shigella sonnei. N Engl J Med 1994;331:579–84).

Chemicals/Toxins

March 2003 New York Muriatic (hydrochloric) 3 Acid, used to adjust pool water pH, was spilled on the floor of an indoor swimming pool/

acid membership club. The resulting fumes caused respiratory symptoms among three persons in the

vicinity, all of whom were taken to an emergency department for treatment and were subsequently

released.

July 2004 Nebraska Microcystin toxin 20 All affected persons were swimming in a lake that was experiencing a blue-green algae bloom, a

(blue-green algae) common occurrence in Nebraska lakes during late summer months. Symptoms included rashes,

diarrhea, cramps, nausea, vomiting, and fevers. The lake was found to have >15 ppb of

microcystin toxin. The lake was closed to public use while the toxin levels remained high. A

nearby lake in the same county reported a similar outbreak during July, with two ill persons

involved.

Unidentified

March 2004 Illinois Suspected 57 A physician reported six members of a family experienced respiratory illness after a visit to a

chloramines local hotel’s indoor pool area. The subsequent investigation uncovered 51 additional cases related

to this pool. Symptoms included burning eyes (77%), cough (47%), and fatigue (25%), among

others. Exposure to pool water was a risk factor for illness. One child with asthma was

hospitalized after the exposure. Chloramines were suspected as the source of the “strong

chlorine-like odor” that visitors noticed in the pool area. A similar outbreak at another Illinois hotel

in January 2004, with 22 cases, also was attributed to chloramines in the indoor pool area

underscoring the importance of air quality at indoor recreational water facilities.

August 2004 New Mexico Suspected 16 A chlorinated, indoor pool at a membership club was the site of an outbreak suspected to involve

chloramines inhaled chloramines. Inadequate ventilation in the pool area was believed to be a contributing

factor. Symptoms included both acute respiratory and gastrointestinal complaints, reinforcing the

concept that diarrhea and vomiting associated with recreational water can have chemical

etiologies as well as infectious ones. Five other outbreaks described in this report have similar

characteristics to this one, including illness suspected to be caused by chemicals in the indoor

pool area’s air and water. Because of the difficulty of measuring transient airborne chloramine

levels exact etiologies were not confirmed. All these outbreaks (with a total of 104 cases)

demonstrate the need for good disinfection and maintenance of water quality along with adequate

ventilation of indoor recreational water venues.

Vibrio infections

July 2004 Mississippi Vibrio vulnificus 1 (1) An adult male with a history of hepatitis C and cirrhosis of the liver sustained an injury to his

chest wall from a bottle rocket while at a marine beach with a group of friends. He used ocean

water to clean the wound and was hospitalized 2 days later with infection of the injured site. The

Vibrio was cultured from his blood. After 2 days in the hospital, the patient died from complications of the infection; this was the only reported death from Vibrio site infection during 2003–2004

in Mississippi.

August 2004 North Carolina V. alginolyticus and 1 A teenaged female was surfing at a coastal beach and cut her left calf on the fin of her surfboard

V. parahaemolyticus while in the water. The wound was sutured at a local emergency department. After a 3-day

incubation period, the patient reported to a Maryland hospital with cellulitis at the injury site.

Incision and drainage was performed, and the surfer was treated with antibiotics and hospitalized

for 5 days. Both species of Vibrio were cultured from the wound exudate (this was the only

reported recreational water case during 2003–2004 to have two separate Vibrio species

identified).

August 2004 Virginia V. parahaemolyticus 1 An adult male was fishing at a coastal salt water site, when he was accidentally hit in the eye with

his fishing hook while cutting his line. The eye became watery and irritated and days later he saw

a physician for treatment. Antibiotics were successfully administered and the patient fully

recovered without the need to be hospitalized.

September 2004 Florida V. parahaemolyticus 1 An elderly man was found in the water of a brackish lagoon in the aftermath of Hurricane Ivan. He

had sustained an injury on his left leg from the debris. Incision, drainage, and a skin graft were all

eventually needed. His infection, which was confirmed by culturing the wound exudate, was

probably exacerbated by additional risk factors: diabetes and use of prednisone for arthritis, both

of which can lead to an immunocompromised state.

No. of

Date of State in which cases

WBDO WBDO occurred Etiologic agent (deaths) Description of WBDO
Vol. 55 / SS-12 Surveillance Summaries 31

Surveillance for Waterborne Disease and Outbreaks Associated

with Drinking Water and Water not Intended for Drinking —

United States, 2003–2004

Jennifer L. Liang, DVM1,2

Eric J. Dziuban1,3

Gunther F. Craun, MPH4

Vincent Hill, PhD, PE1

Matthew R. Moore, MD5

Richard J. Gelting, PhD6

Rebecca L. Calderon, PhD7

Michael J. Beach, PhD1

Sharon L. Roy, MD1

1Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases (proposed), CDC

2Epidemic Intelligence Service, Office of Workforce and Career Development, CDC

3 CDC Experience Fellowship, Office of Workforce and Career Development, CDC 4Gunther F. Craun and Associates, Staunton, Virginia 5Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases (proposed), CDC 6Division of Emergency and Environmental Health Services, National Center for Environmental Health, CDC

7U.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

State and Territorial Epidemiologists have maintained a collaborative Waterborne Disease and Outbreaks Surveillance System for collecting and reporting data related to occurrences and causes of waterborne disease and outbreaks (WBDOs). This surveillance system is the primary source of data concerning the scope and effects of

WBDOs in the United States.

Reporting Period: Data presented summarize 36 WBDOs that occurred during January 2003–December 2004

and nine previously unreported WBDOs that occurred during 1982–2002.

Description of System: The surveillance system includes data on WBDOs associated with drinking water, water

not intended for drinking (excluding recreational water), and water of unknown intent. Public health departments in the states, territories, localities, and 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) are primarily responsible for detecting and investigating WBDOs and voluntarily

reporting them to CDC by using a standard form.

Results: During 2003–2004, a total of 36 WBDOs were reported by 19 states; 30 were associated with drinking

water, three were associated with water not intended for drinking, and three were associated with water of

unknown intent. The 30 drinking water-associated WBDOs caused illness among an estimated 2,760 persons

and were linked to four deaths. Etiologic agents were identified in 25 (83.3%) of these WBDOs: 17 (68.0%)

involved pathogens (i.e., 13 bacterial, one parasitic, one viral, one mixed bacterial/parasitic, and one mixed

bacterial/parasitic/viral), and eight (32.0%) involved chemical/toxin poisonings. Gastroenteritis represented 67.7%

of the illness related to drinking water-associated WBDOs; acute respiratory illness represented 25.8%, and

dermatitis represented 6.5%.

The classification of deficiencies contributing to WBDOs has been revised to reflect the categories of concerns

associated with contamination at or in the source water, treatment facility, or distribution system (SWTD) that

are under the jurisdiction of water utilities, versus those at points not under the jurisdiction of a water utility or

at the point of water use (NWU/POU), which includes commercially bottled water. A total of 33 deficiencies

were cited in the 30 WBDOs associated with drinking

water: 17 (51.5%) NWU/POU, 14 (42.4%) SWTD,

and two (6.1%) unknown. The most frequently cited

NWU/POU deficiencies involved Legionella spp. in the

Corresponding author: Jennifer L. Liang, DVM, Division of Parasitic

Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases

(proposed), 4770 Buford Hwy., NE, MS F-22, Atlanta, GA 30341.

Telephone: 770-488-7781; Fax: 770-488-7761; E-mail: jliang@cdc.gov.
32 MMWR December 22, 2006

drinking water system (n = eight [47.1%]). The most frequently cited SWTD deficiencies were associated with

distribution system contamination (n = six [42.9%]). Contaminated ground water was a contributing factor in

seven times as many WBDOs (n = seven) as contaminated surface water (n = one).

Interpretation: Approximately half (51.5%) of the drinking water deficiencies occurred outside the jurisdiction

of a water utility in situations not currently regulated by EPA. The majority of the WBDOs in which deficiencies

were not regulated by EPA were associated with Legionella spp. or chemicals/toxins. Problems in the distribution

system were the most commonly identified deficiencies under the jurisdiction of a water utility, underscoring the

importance of preventing contamination after water treatment. The substantial proportion of WBDOs involving

contaminated ground water provides support for the Ground Water Rule (finalized in October 2006), which

specifies when corrective action is required for public ground water systems.

Public Health Actions: CDC and EPA use surveillance data to identify the types of water systems, deficiencies,

and etiologic 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

improved water-quality regulation development. The growing proportion of drinking water deficiencies that are

not addressed by current EPA rules emphasizes the need to address risk factors for water contamination in the

distribution system and at points not under the jurisdiction of water utilities.

Introduction

During 1920–1970, statistical data regarding U.S. waterborne-disease outbreaks were collected by 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 maintained a

collaborative Waterborne Disease and Outbreak Surveillance System (WBDOSS) that tracks the occurrences and

causes of waterborne disease and outbreaks (WBDOs)

associated with drinking water. WBDOs associated with

recreational water were added to the surveillance system in

1978 (2); WBDOs associated with occupational settings,

water not intended for drinking (WNID)* and commercially bottled water were added in 1999 (3); and WBDOs

associated with drinking water contaminated at the point

of use, contaminated ice and beverages made with contaminated water, and beverages contaminated as a result of

plumbing failures in drink mix/soda machines have been

added to this report. This Surveillance Summary includes

data from 30 WBDOs related to drinking water, three

WBDOs related to WNID, and three WBDOs related to

water of unknown intent (WUI). Nine previously unreported outbreaks also have been included in this report.

Recreational water-associated disease and outbreaks have

been presented in a separate report (4). This Surveillance

Summary also introduces multiple changes in the WBDOSS

to better characterize the breadth of waterborne-disease

challenges in the United States.

Waterborne disease and outbreak surveillance activities

1) characterize the epidemiology of WBDOs; 2) identify

changing trends in the etiologic agents and other risk factors associated with WBDOs; 3) identify major deficiencies in providing safe drinking water; 4) encourage public

health personnel to detect and investigate WBDOs; and 5)

foster collaboration among local, state, federal, and international agencies on initiatives to prevent waterborne disease. Data from this surveillance system are useful for

identifying major deficiencies in providing safe drinking

water, can influence research priorities, and can lead to

improved focus in water-quality regulation development.

However, the statistics reported in this report represent only

a portion of the burden of illness associated with water

exposure. In general, the surveillance information does not

include endemic, nonoutbreak-related waterborne-disease

risks, and reliable estimates of the number of unrecognized

WBDOs are not available.

Background

U.S. Environmental Protection Agency

Drinking Water Regulations

Public water systems are regulated under the Safe Drinking Water Act (SDWA) of 1974 and its subsequent 1986

and 1996 amendments (Table 1) (5–7). SDWA authorizes

EPA to set national standards to protect public drinking

water and its sources against naturally occurring or manmade contaminants. Previously set standards by which * Additional terms have been defined (Appendix A, Glossary of Definitions).
Vol. 55 / SS-12 Surveillance Summaries 33

microbial contamination is regulated include the Total

Coliform Rule (TCR), Surface Water Treatment Rule

(SWTR), Interim Enhanced SWTR (IESWTR), and Long

Term 1 Enhanced SWTR (LT1ESWTR). In addition, EPA’s

lead, copper, and arsenic rules prescribe action levels at which

a system must take corrective steps (8,9). These rules have

been described in more detail in a previous report (3).

All public water systems are required by TCR to monitor

for total coliforms at a prescribed frequency (10,11). SWTR

(12) and IESWTR (13) apply to public systems that serve

>10,000 persons and surface water or ground water under

the direct influence of surface water. These two rules are

intended to protect the public against exposure to Giardia

intestinalis, Cryptosporidium spp., viruses, Legionella spp.,

and other selected pathogens. LT1ESWTR applies to public systems that serve <10,000 persons and is intended to

improve the control of microbial pathogens, especially

Cryptosporidium spp. (14). An additional regulation, the

Filter Backwash Recycling Rule, requires the return of

recycle flows to the water treatment process so that microbial contaminant removal is not compromised (15).

Recently finalized microbial and disinfection byproducts regulations include the Long Term 2 Enhanced

Surface Water Treatment Rule (LT2ESWTR) and the Stage

2 Disinfectants and Disinfection By-products Rule

(DBPR2). These regulations were developed simultaneously

to address risk tradeoffs between the control of pathogens

and limiting exposure to disinfection by-products (DBPs)

that can form in water from the disinfection process used

to control microbial pathogens (16).

LT2ESWTR (17,18) requires the use of treatment techniques and monitoring, reporting, and public notification

for all public water systems that use surface water sources.

Key provisions include the following: source water monitoring for Cryptosporidium spp.; additional treatment for

filtered systems on the basis of source-water Cryptosporidium

concentrations; inactivation of Cryptosporidium by all

unfiltered systems; disinfection profiling and benchmarking

to ensure continued levels of microbial protection while

system operators take steps to comply with new DBP limits; and covering, treating, or implementing a risk management plan for uncovered finished water storage facilities.

DBPR2 applies to all community and all nontransient,

noncommunity water systems that use a disinfectant other

than ultraviolet light (17). DBPR2 requires systems to meet

maximum contaminant levels for total trihalomethanes and

five haloacetic acids at each monitoring site in the distribution system, determine if they are experiencing shortterm peaks in DBP levels, and better identify monitoring

sites at which customers are exposed to high DBP levels.

The 1996 SDWA amendments require EPA to develop

regulations that mandate disinfection of public ground

water systems, as necessary, to protect the public health.

The Ground Water Rule (GWR) (finalized by EPA in

October 2006) specifies when corrective action, including

disinfection, is required to protect consumers from bacteria and viruses (19). Additional information is available at

http://www.epa.gov/safewater/gwr.html. Requirements

include periodic sanitary surveys to identify deficiencies,

hydrogeologic sensitivity assessments for nondisinfected

systems, source-water microbial monitoring from certain

systems, and compliance monitoring for systems that disinfect to ensure adequate inactivation or removal of viruses.

SDWA Wellhead Protection Program requires every state

to develop a program to delineate wellhead protection

areas in which sources of contamination are managed to

minimize ground water contamination (19).

Every 5 years, EPA is required to publish a list of contaminants that are known or anticipated to occur in public

water systems and that might need to be regulated. The

first drinking water Contaminant Candidate List (CCL1)

was issued in 1998 and included 50 chemical and 10

microbial contaminants (20). However, EPA decided not

to regulate Acanthamoeba, which was on the first list. The

second Contaminant Candidate List 2 (CCL2) carried forward nine microbiologic contaminants from CCLl, excluding Acanthamoeba (21). EPA also must establish criteria

for a program to monitor unregulated contaminants and

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

Ground Water Rule (proposed) 2000

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 finalized 2006
34 MMWR December 22, 2006

publish a list of contaminants to be monitored (22–25).

Microorganisms on this list include those for which analytical methods are available (Aeromonas) and those for

which analytical methods are being developed (i.e.,

Helicobacter pylori, cyanobacteria, coxsackieviruses,

microsporidia, adenoviruses, and caliciviruses). An ongoing screening survey for Aeromonas and selected chemical

contaminants will help determine whether these should be

considered for or excluded from regulation.

Methods

Data Sources

Public health departments in the states, territories,

localities, and Freely Associated States (FAS) (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 and investigating

WBDOs, which they report voluntarily to CDC by 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 the WBDO (e.g., cases, time, and location); results from

epidemiologic studies; results from clinical specimen and

water sample testing; and other factors potentially contributing to the WBDO (e.g., environmental concerns, disinfection deficiencies, and filtration problems). CDC annually

requests reports from state, territorial, and FAS epidemiologists or persons designated as WBDO surveillance coordinators and obtains additional information regarding water

quality and water treatment as needed. Information also

can be solicited from other CDC surveillance systems and

confirmed with the state, territory, locality, or FAS for

inclusion as a WBDO. Numerical and text data are

abstracted from the WBDO report form and supporting

documents and entered into a database for analysis.

Although reports of WBDOs are collected through the

WBDOSS, the cases and outbreaks associated with drinking water, WNID, and WUI are analyzed and published

separately from the cases and outbreaks associated with recreational water (4).

Definitions

The unit of analysis for the WBDOSS is typically an

outbreak, not an individual case of a waterborne disease.

Two criteria must be met for an event to be defined as a

waterborne outbreak associated with drinking water, WNID

(excluding recreational water) or WUI. First, two or more

persons must be epidemiologically linked by location of

exposure to water, time, and illness. This criterion is waived

for single cases of laboratory-confirmed primary amebic

meningoencephalitis (PAM) and for single cases of chemical/toxin poisoning if water-quality data indicate contamination by the chemical/toxin. Second, the epidemiologic

evidence must implicate water as the probable source of

illness. Reported cases and outbreaks associated with contaminated drinking water; contaminated commercially

bottled water, ice, or beverages made with contaminated

water; and deficiencies of equipment/devices for which water

is used or distributed (e.g., beverages contaminated by

plumbing failures in drink mix/soda machines) are classified as WBDOs. WBDOs associated with cruise ships are

not summarized in this report. Tabulation of WBDOs and

associated cases is based on location of water exposure, not

on state of residence of the ill persons.

Numerous types of drinking water systems exist and have

been outlined (Figure 1). Public water systems, which are

classified as either community or noncommunity , are regulated under SDWA. Of the approximately 167,012 public

water systems in the United States, 112,948 (67.6%) are

noncommunity systems, including 93,210 transient systems and 19,738 nontransient systems; 54,064 (32.4%)

are community systems. Despite representing a minority

of water systems, community systems serve 264 million

persons (approximately 93.9% of the U.S. population)

(26). Furthermore, a limited number of community systems (15%) provide water to 90% of the community system population (26). Noncommunity, nontransient

systems provide water to 6.9 million persons, and noncommunity, transient systems provide water to 12.9 million persons (by definition, these populations also use

another type of water system at their residences, except for

the limited number of permanent residents of nontransient

systems) (26). Although the majority of public water systems (91.6%) are supplied by ground water, more persons

(63.4%) drink from public systems served by surface water (26). Approximately 15.0% of the U.S. population relies on individual water systems that are privately owned

(27). In previous Surveillance Summaries, commercially

bottled water, when linked with a WBDO, was classified

as an individual water system; these WBDOs are now classified as bottled water. WNID is defined as 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.

WNID does not include recreational water, which is dis-
Vol. 55 / SS-12 Surveillance Summaries 35

cussed in a separate Surveillance Summary (4). WBDOs with

more than one implicated water system type are tabulated

and analyzed as mixed water systems (e.g., noncommunity

and individual).

Source water is defined as the untreated water (i.e., raw

water) used to produce drinking water. WBDOs with more

than one implicated water source are tabulated and analyzed as mixed water sources (e.g., lake and well). For WNID

or WUI, primary water exposure is defined as the source of

contaminated water.

Water setting is defined as the location of ill person’s

exposure to the contaminated water. The setting applies to

drinking water, WNID, and WUI.

The purpose of this surveillance system is not only to

evaluate the relation between water and reported outbreaks

and disease, but also to identify system breakdowns,

operator errors, and other engineering-related activities that

lead to outbreaks. To understand the circumstances and

system 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 been

classified 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 the

WBDO report form. Although WBDOs without waterquality data might have been included in this report,

reports that lacked epidemiologic data, linking the outbreak to water, have been excluded.

A classification of I indicates that adequate epidemiologic

and water-quality data were reported. However, this classification does not necessarily imply that the investigation

was optimally conducted nor does a classification of II, III,

or IV imply that the investigation was inadequate or

incomplete. WBDOs and their resulting investigations

occur under different circumstances, and not all WBDOs

can or should be rigorously investigated. In addition,

WBDOs that affect few persons are more likely to receive a

classification of III or IV because of the limited sample size

available for analysis.

Changes in the 2003–2004 Surveillance

Summary

Names, definitions, and other parameters in this report

have been modified and expanded to better reflect the changing epidemiology of WBDOs and capture the wide scope

of water-related disease. This section highlights those

changes.

FIGURE 1. Types of drinking water systems

* 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.

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) §
36 MMWR December 22, 2006

TABLE 2. Deficiency classification for drinking water, water not intended for drinking (excluding recreational water), and water 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, or inadequate or no filtration)

4: Distribution system deficiency, including storage (e.g., cross-connection, backflow, contamination of water mains during construction or repair)

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, or corrosion of pipes)

7: Deficiency in building/home-specific water treatment after the water meter or property line

8: Deficiency or contamination of equipment/devices 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

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.

†Contamination of drinking water and deficiencies occurring after the water meter or outside the jurisdiction of a water utility (e.g., in a service line leading

to a house or building, in the plumbing inside a house or building, during shipping or hauling, during storage other than in the distribution system, or at

point of use).

TABLE 3. Classification of investigations of waterborne disease and outbreaks — United States

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
Vol. 55 / SS-12 Surveillance Summaries 37

Title

The title of this Surveillance Summary has been changed.

The change in the title of this report emphasizes and better represents the public health importance of single cases

of waterborne disease and disease associated with water

exposures other than drinking water and recreational water.

Etiologic Agents

Etiologic agents are typically identified through clinical

specimen testing. If more than one agent is identified, only

those agents that individually represent >5% of positive

clinical specimens appear in the tables and calculations as

etiologic agents for that WBDO. Occasionally, clinical specimen data are unavailable, but water sample testing implicates a particular etiologic agent that is consistent with the

presenting illness. In these situations, the agent identified

by water testing is listed as the etiologic agent for that

WBDO. WBDOs in which the etiologic agent is unconfirmed or unknown are listed as unidentified, even when

other data (e.g., clinical findings) are suggestive of a particular pathogen or chemical/toxin. In previous reports, the

term “acute gastrointestinal illness (AGI)” was used to

indicate WBDOs of unidentified etiology associated with

gastrointestinal symptoms. Because AGI refers to a type of

illness and not to an etiologic agent, the term “unidentified” is now used to describe WBDOs with unknown

etiology.

When each etiologic agent is of the same agent type (i.e.,

bacterial, chemical/toxin, parasitic, or viral), the WBDO is

analyzed within that category (e.g., an outbreak with both

Cryptosporidium spp. and Giardia spp. will be analyzed as a

parasitic outbreak). When agents represent more than one

type, the WBDO is analyzed as a mixed-agent WBDO (e.g.,

an outbreak with both Giardia spp. and Salmonella spp.

will be analyzed as a mixed parasitic and bacterial outbreak).

Predominant Illness

All WBDOs are categorized according to predominant illness. Whereas the illness associated with a WBDO generally

includes only one category of symptoms (e.g., gastroenteritis), WBDOs do occur where the symptoms cluster into more

than one category (e.g., gastroenteritis and dermatitis). Therefore, in this report, any illness symptom reported by >50%

of patients will be listed; multiple illnesses will be listed for

a single WBDO, if applicable. Mixed illness WBDOs are

analyzed separately from single illness WBDOs.

Case Counts and Deaths

The number of deaths associated with each WBDO has

been added to the case counts. No deaths occurred unless

noted. This change provides greater information on the

severity of illness associated with each WBDO.

Deficiencies

Water utilities manage the drinking water in public systems before the water reaches the water meter (or before

the property line if the distribution system is not metered).

These public drinking water systems are subject to EPA

regulations. Drinking water concerns arising after the meter

or property line (e.g., Legionella colonization in plumbing,

plumbing contamination and cross-connections within

buildings and homes, and drink mix/soda machine deficiencies) might not be under the jurisdiction of water utilities and might not be regulated under current EPA drinking

water rules. To characterize drinking water concerns that

might have different oversight, the classification of deficiencies leading to WBDOs has been modified in this report.

The new deficiency classification (Table 2) provides greater

detail concerning the circumstances and risk factors that

led to illness and clarifies deficiencies that might require

different types of public health responses.

In the old deficiency classification (formerly deficiencies

1–5), antecedent circumstances related to WBDOs that

occurred outside the jurisdiction of a water utility were 1)

classified with water distribution system deficiencies that

were within the jurisdiction of a water utility (formerly

deficiency 4); 2) classified as miscellaneous deficiencies (formerly deficiency 5); or 3) not classified at all (e.g., Legionella

colonization in plumbing). In the new deficiency classification, a clear distinction is made between contamination

occurring at or in the source water, treatment facility, or

distribution system (SWTD) (deficiencies 1–4), which are

under the jurisdiction of a water utility if a public water

system is involved versus contamination at points not

under the jurisdiction of a water utility or at the point of

use (NWU/POU) (i.e., deficiencies 5A, 6–11, and 99A

and 99B). The NWU/POU deficiencies include WBDOs

associated with drinking water contaminated during shipping, hauling, storing, or use; commercially bottled water;

ice or beverages made with contaminated water; and deficiencies of equipment/devices in which water is used or

distributed (e.g., beverages contaminated by plumbing failures in drink mix/soda machines). For WBDOs involving

consumption or contact with WNID and WUI, separate

deficiency classifications (i.e., deficiencies 5B, 5C, 12, 99C,

and 99D) are used.

The reporting and analysis of deficiencies also have changed

to emphasize that individual WBDOs might be associated

with more than one deficiency. Instead of reporting and analyzing only the primary deficiency when multiple deficien-
38 MMWR December 22, 2006

cies have been identified, all deficiencies are now considered.

Identifying only the primary deficiency might be difficult

because more than one deficiency might have resulted in

contamination of water that would result in illness. To

reflect this complexity, tables and figures that report deficiency information report all deficiencies that have likely contributed to the WBDO. Therefore, the total number of

deficiencies is greater than the total number of WBDOs.

Water System Type

Drinking water systems remain categorized as community, noncommunity, or individual systems. For the 1999–

2000 and 2001–2002 Surveillance Summaries, WBDOs

linked to commercially bottled water and WNID were classified as individual water systems for analysis purposes

(3,28). For 2003–2004, to distinguish between piped and

nonpiped drinking water, the definition of an individual

drinking water system no longer includes commercially

bottled water and WNID. WBDOs associated with commercially bottled water are now classified separately (i.e.,

bottled). Separating piped from nonpiped water also distinguishes between drinking water systems regulated by

EPA (community and noncommunity) and the FDA (i.e.,

bottled). WBDOs associated with WNID no longer have a

water system type designation because the risk factors

associated with these WBDOs are not relevant to drinking

water systems.

Analyses involving water system types have also changed.

If a WBDO involving more than one water system type

occurs, the WBDO is classified and analyzed as a mixed

water system. Furthermore, all analyses that involve water

system types are limited to WBDOs with deficiencies 1–4

and deficiency 99 when a water system can be identified

but insufficient information concerning the deficiency is

available. Under the revised deficiency classification, the

only deficiencies relevant to the type of drinking water system associated with the WBDO are deficiencies 1–4 (i.e.,

surface water contamination, ground water contamination,

water treatment deficiencies, and distribution system

contamination).

Water Source

The only deficiencies relevant to the type of drinking

water source involved in the WBDO are deficiencies 1–3

(i.e., surface water contamination, ground water contamination, and water treatment deficiencies). Therefore, all

analyses presented in this report that involve source water

type are limited to WBDOs with deficiencies 1–3. If a

WBDO involves more than one source water type, the

WBDO is classified and analyzed as a mixed source WBDO.

Legionella

Although outbreaks of Pontiac fever (PF) have been

included in the WBDOSS since 1981, outbreaks of

Legionnaires’ disease (LD) only have been included since

the 2001–2002 surveillance period (28). During this

period, all PF and LD outbreaks were listed in the drinking water Surveillance Summary in a table separate from the

tables listing other drinking water-associated WBDOs; the

single PF outbreak associated with recreational water was

discussed in the recreational water Surveillance Summary

(29). Beginning with the 2003–2004 Surveillance Summary, PF and LD outbreaks associated with drinking water

are included in the same line lists with other drinking waterassociated WBDOs. Similarly, PF and LD outbreaks associated with recreational water are listed and discussed in

the 2003–2004 Surveillance Summary of recreational waterassociated WBDOs (4). Inclusion and analysis of PF and

LD outbreaks with other drinking water-associated

WBDOs is a reflection of the changing epidemiology of

WBDOs. Legionella outbreaks that occur in association with

WNID or WUI also are listed and discussed in this report.

Water Not Intended for Drinking and Water

of Unknown Intent

In previous Surveillance Summaries, WBDOs (excluding

Legionella outbreaks) associated with WNID or with WUI

were integrated into the drinking water WBDO line lists.

Beginning with this report, WBDOs (including Legionella

outbreaks) associated with WNID or with WUI are listed

in separate tables to distinguish the different water types.

Strength of Evidence Classification

for Waterborne Disease and Outbreaks

Single cases of PAM or chemical/toxin poisoning are now

given strength of evidence classifications (Table 3) along

with the other WBDOs. These single cases do not receive

rankings higher than III because relative risks, odds ratios,

and p values are not calculated from single cases.

Results

During 2003–2004, 19 states reported 36 WBDOs (i.e.,

14 for 2003 and 22 for 2004). These WBDOs were associated with water intended for drinking (n = 30), WNID

(n = three), and WUI (n = three) and are tabulated by year

and state (Tables 4–6).
Vol. 55 / SS-12 Surveillance Summaries 39

Waterborne Disease and Outbreaks

Associated with Water Intended

for Drinking

The 30 drinking water-associated WBDOs (i.e., 12 during 2003 and 18 during 2004) were reported by 18 states

(Figure 2). The number of drinking water-associated

WBDOs reported for 2003–2004 is similar to that reported

for 2001–2002 (n = 36, including the five previously

unreported outbreaks for 2002 [Table 7; Figure 3]). WBDOs

associated with drinking water occurred throughout the

year (Figure 4). Five states (Florida, New Jersey, New York,

Ohio, and Pennsylvania) reported the highest number of

drinking water-associated WBDOs (three each) for 2003–

2004. Selected WBDO descriptions have been reported

(Appendix B, Descriptions of Selected Waterborne Disease

and Outbreaks (WBDOs) Associated with Drinking Water,

Water Not Intended for Drinking, and Water of Unknown

Intent).

The 30 drinking water-associated WBDOs reported for

2003–2004 caused illness among approximately 2,760

persons and resulted in four deaths. The median number

of persons affected in a WBDO was seven (range: 1–1,450).

Twenty-nine WBDOs were associated with either acute

respiratory illness (ARI) or AGI, and one WBDO was associated with both ARI and AGI. All ARI outbreaks were

associated with exposure to Legionella spp. (Figure 5).

Seven (23.3%) of the 30 drinking water-associated

WBDOs were given a strength of evidence Class I ranking

on the basis of epidemiologic and water-quality data; one

(3.3%) was ranked as Class II; 20 (66.7%) were ranked as

Class III; and two (6.7%) were ranked as Class IV. Drinking water-associated 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 involved in

each WBDO was associated with the summarized variable.

WBDOs were not included if the type of deficiency did

TABLE 4. Waterborne-disease outbreaks associated with drinking water (n = 12), by state — United States, 2003

No. of

Predominant cases* Type of Water

State Month Class Etiologic agent illness (n = 819) system† Deficiency§ source Setting

Florida Jan II Unidentified¶ Gastroenteritis 419 Bottle 11C Spring Sports complex

Florida Nov III Bromate and other Gastroenteritis 2 Bottle 9 Unknown Private residence

byproducts of disinfection

Illinois Jul I Unidentified Gastroenteritis 180 Ncom 99A Well Water park

Maine Dec III Cleaning product Gastroenteritis 2 Bottle 10B Spring Unknown

Maryland** Oct III Legionella pneumophila Acute respiratory 7 Com 5A Well Hotel

serogroup 1

Michigan Sep I Unidentified Gastroenteritis 4 Com 11D Well Worksite

Minnesota Jun I Copper Gastroenteritis 4 Com 8 River, Restaurant

 stream

Minnesota Nov I Copper Gastroenteritis 5 Com 8 Lake Restaurant

New York Mar III Sodium hydroxide Dermatitis 4 Com 3 Well Community

Ohio Nov I Campylobacter jejuni and Gastroenteritis 57 Ind 1 Pond Worksite

Shigella spp.††

Utah Jul III Unidentified Gastroenteritis 25 Ncom 99A Unknown Camp

Washington May III Campylobacter spp.§§ Gastroenteritis 110 Ind 2, 4 Well Farm

* No deaths were reported.

† Com: community; Ncom: noncommunity; Ind: individual; Bottle: commercially bottled water. 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 yearround 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.

§ Refer to Table 2 - Deficiency classification for drinking water, water not intended for drinking (excluding recreational water), and water of unknown intent.

¶ Etiology unidentified; norovirus suspected based on incubation period, symptoms, and duration of illness.

** Source: CDC. Legionnaires’ disease associated with potable water in a hotel—Ocean City, Maryland, October 2003–February 2004. MMWR

2005;54:165–8.

†† Sixteen persons had stool specimens that tested positive for C. jejuni, and two persons had stool specimens that tested positive for Shigella spp. §§ Nine persons had stool specimens that tested positive for Campylobacter spp., and three persons had stool specimens that tested positive for C. jejuni.
40 MMWR December 22, 2006

not reflect the summarized variable (e.g., the source of raw

untreated water would unlikely be relevant for a Legionella

outbreak associated with a building plumbing system).

Etiologic Agents

Twenty-five (83.3%) of the 30 drinking water-associated

WBDOs were of known etiology; 17 (68.0%) were attributed to an infectious etiology, and eight (32.0%) were

attributed to chemical/toxin poisoning. Of the 17 WBDOs

with known infectious etiology, 13 (76.5%) were caused

by bacteria (eight [61.5%] of which were caused by

Legionella spp.), two (11.8%) were caused by more than

one etiologic agent type, one (5.9%) was caused by a parasite, and one (5.9%) was caused by a virus. Five (16.7%)

of the 30 drinking water-associated WBDOs were of

unknown etiology. The distribution of etiologic agents for

TABLE 5. Waterborne-disease outbreaks associated with drinking water (n = 18), by state — United States, 2004

No. of

 cases

Predominant (deaths)* Type of Water

State Month Class Etiologic agent illness (n = 1,941) system† Deficiency§ source Setting

Florida Oct III Gasoline byproducts Gastroenteritis 1 Bottle 99B Unknown Private residence

Maryland Dec III Legionella pneumophila Acute respiratory 6 (2) Com 5A Well Condominium

serogroup 1

Montana Aug III Salmonella typhimurium Gastroenteritis 70 Ncom 3, 4 Well Restaurant

New Jersey Apr III Sodium hydroxide Dermatitis 2 Com 3 Well Community

New Jersey Jun III L. pneumophila Acute respiratory 2 Com 5A River Apartment

serogroup 1

New Jersey Jul III L. pneumophila Acute respiratory, 2 (1) Com 5A River Senior housing

serogroup 1 Gastroenteritis¶ center

New York Jan III L. micdadei Acute respiratory 2 Com 5A Reservoir Hospital

New York May III L. pneumophila Acute respiratory 2 Com 5A Reservoir Hospital

serogroup 1

Ohio Jan III Campylobacter jejuni, Gastroenteritis 82 Com 4 Well Factory

Campylobacter lari,

Cryptosporidium spp.,

and Helicobacter

canadensis**

Ohio Jul I C. jejuni, norovirus, and Gastroenteritis 1450 Ncom/Ind 2, 4 Well Restaurant, bar

Giardia intestinalis†† camp, and

tourist attraction

Pennsylvania Jan I Norovirus Gastroenteritis 70 Ncom 6 Pond Ski resort

Pennsylvania Jun III Unidentified Gastroenteritis 174 Ncom 3 Well Camp

Pennsylvania Apr III L. pneumophila Acute respiratory§§ 3 (1) Com 5A Well, lake, Nursing home

serogroup 1 and creek

South Carolina Jul III Copper Gastroenteritis 7 Com 8 Lake Restaurant

Texas Sep IV L. pneumophila Acute respiratory 3 Com 5A Well Hospital

serogroup 1

Virginia Aug IV Campylobacter spp. Gastroenteritis 34 Com 4 Well Community

Vermont Jun III G. intestinalis Gastroenteritis 11 Ncom 4 Well Camp

Wisconsin Dec III C. jejuni Gastroenteritis 20 Ncom 2 Well Restaurant

* Deaths are indicated in parentheses if they occurred.

† Com: community; Ncom: noncommunity; Ind: individual; Bottle: commercially bottled water. 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 yearround 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.

§ Refer to Table 2 - Deficiency classification for drinking water, water not intended for drinking (excluding recreational water), and water of unknown intent.

¶ Two persons had cough, fever, and diarrhea.

** Seven persons had stool specimens that tested positive for C. jejuni, one person had a stool specimen that tested positive for C. lari, one person had

a stool specimen that tested positive for Cryptosporidium spp., and one person had a stool specimen that tested positive for H. canadensis. †† Sixteen persons had stool specimens that tested positive for C. jejuni, nine persons had stool specimens that tested positive for norovirus, and three

persons had stool specimens that tested positive for G. intestinalis. Only one person (<5%) had a stool specimen that tested positive for S. typhimurium

— this pathogen is not included in the table. §§ Legionnaires’ disease was diagnosed in two persons, and Pontiac fever was diagnosed in one person.
Vol. 55 / SS-12 Surveillance Summaries 41

TABLE 6. Waterborne-disease outbreaks associated with water not intended for drinking (excluding recreational water) and water

of unknown intent (n = six), by state — United States, 2003–2004

No. of

 cases

Month/ Predominant (deaths)* Primary

State Year Class Etiologic agent illness (n = 36) Deficiency† water exposure Setting

New York Jul 2003 IV Legionella pneumophila Acute respiratory 2 5C Unknown Nursing home

serogroup 1

New York Jul 2004 III L. pneumophila Acute respiratory 2 (1) 5B Cooling tower Nursing home

serogroup 1

North Carolina Sep 2004 I L. pneumophila Acute respiratory 7 (3) 5B Cooling tower Nursing home,

serogroup 1 hospital, and

factory

Ohio Jul 2004 I L. pneumophila Acute respiratory§ 13 5C Unknown Worksite

serogroup 1

Texas Oct 2004 IV L. pneumophila Acute respiratory 2 5C Unknown Hotel

serogroup 1

Wisconsin Jul 2003 IV Escherichia coli O157:H7 Gastroenteritis 10 12 Broken septic line Camp

* Deaths are indicated in parentheses if they occurred.

†Refer to Table 2 - Deficiency classification for drinking water, water not intended for drinking (excluding recreational water), and water of unknown intent.

§Two confirmed cases of Legionnaires’ disease and 11 probable cases with symptoms consistent with Pontiac fever.

No. of

oubreaks

No. of

states

>4 0

3 5

2 2

1 11

0 32

FIGURE 2. Number* of waterborne-disease outbreaks

associated with drinking water — United States, 2003–2004

* n = 30; numbers are dependent on reporting and surveillance activities

in individual states and do not necessarily indicate that more outbreaks

occurred in a given state.

the 30 drinking water-associated WBDOs has been reported

(Figure 6).

Bacteria. Thirteen WBDOs affecting 318 persons were

attributed to bacterial infections: eight Legionella spp. outbreaks, three Campylobacter spp. outbreaks, one Salmonella

typhimurium outbreak, and one outbreak involving two different bacteria (16 persons had stool specimens that tested

positive for C. jejuni, and two persons had stool specimens

that tested positive for Shigella spp.). Illnesses from these 13

WBDOs resulted in four deaths, all of which were associated with Legionella spp.

Chemicals/Toxins. Eight WBDOs affecting 27 persons

were attributed to chemical/toxin poisoning; no deaths were

reported. Three WBDOs involved high levels of copper

associated with drink mix/soda machines; three WBDOs

were a result of contamination of commercially bottled water

with bromate and other by-products of disinfection, cleaning products, and gasoline by-products; two WBDOs were

a result of large volumes of sodium hydroxide discharged

into community water supplies.

Mixed agents. Two WBDOs were attributed to more than

one type of etiologic agent; no deaths were reported. The

largest reported outbreak affected 1,450 persons and

involved at least one bacterium (i.e., C. jejuni, although

one clinical specimen with S. typhimurium also was

reported), one virus (norovirus), and one parasite (Giardia

intestinalis). The second mixed-agent outbreak affected 82

persons and involved infection with three different bacteria (i.e., C. jejuni, C. lari, and Helicobacter canadensis) and

one parasite (Cryptosporidium spp.).

Parasites. One WBDO attributed to G. intestinalis,

affected 11 persons. No deaths were reported.

Viruses. One WBDO attributed to norovirus affected 70

persons. No deaths were reported.

Unidentified etiologic agents. Five WBDOs involving

AGI of unidentified etiology affected 802 persons; no deaths

were reported. Stool testing to identify a causative agent

was attempted in four of the five outbreaks. In one outbreak at a volleyball tournament, norovirus was suspected

on the basis of incubation period, symptoms, and duration of illness (Florida, January 2003). However, the

implicated water tested negative for norovirus, and patient

samples were not collected for confirmatory testing.
42 MMWR December 22, 2006

TABLE 7. Waterborne-disease outbreaks that were not included in previous surveillance summaries (n = nine), by state/territory —

United States, 1982–2002

No. of

Month/ Predominant cases* Type of Water

State/Territory Year Class Etiologic agent illness (n = 217) system† Deficiency§ source Setting

Maryland Nov 2002 III Legionella pneumophila Acute respiratory 3 Com 5A Reservoir Club

serogroup 1

New York May 1982 III Unidentified Gastroenteritis 16 Ncom 3 Well Restaurant

New York May 1984 II Copper Gastroenteritis 15 Com 4 Reservoir Restaurant

New York Aug 1995 I Unidentified¶ Gastroenteritis 30 Ncom 2, 11E Well Motel

New York Aug 1996 I Unidentified** Gastroenteritis 58 Ncom 2 Well Camp

New York Jul 2002 III Escherichia coli O157:H7 Gastroenteritis 6 Ind 2 Well Private

residence

New York Dec 2002 I Campylobacter jejuni, Gastroenteritis 27 Com 2 Well Apartment

Entamoeba spp., and

Giardia spp.††

Palau Apr 2002 III Entamoeba histolytica Gastroenteritis 59 Ncom 99A Stream Unknown

Virgin Islands§§ Nov 2002 III L. pneumophila Acute respiratory 3 Ncom 5A Reservoir, Hotel

serogroup 1 cistern¶¶

* No deaths were reported.

† Com: community; Ncom: noncommunity; Ind: individual; Bottle: commercially bottled water. 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 yearround 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.

§ Refer to Table 2 - Deficiency classification for drinking water, water not intended for drinking (excluding recreational water), and water of unknown intent.

¶ Etiology unidentified; Norwalk-like virus suspected based on incubation period, symptoms, and duration of illness.

** Etiology unidentified; viral etiology suspected based on incubation period, symptoms, and duration of illness.

†† Three persons had stool specimens that tested positive for C. jejuni; two persons had stool specimens that tested positive for Entamoeba spp., and

one person had a stool specimen that tested positive for Giardia spp. §§ Source: Cowgill KD, Lucas CE, Benson RF, et al. Recurrence of Legionnaires’ disease at a hotel in the United States Virgin Islands over a 20-year

period. Clin Infect Dis 2005;40:1205–7.

¶¶ Rainwater cistern sometimes was supplemented with community water.

FIGURE 3. Number* of waterborne-disease outbreaks associated with drinking water, by year and etiologic agent — United

States, 1971–2004

* n = 803.

†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 spp. were classified separately in this figure.

0

10

20

30

40

50

60

1971 1974 1977 1980 1983 1986 1989 1992 1995 1998 2001† 2004

Year

Mixed agents†

Legionella spp.

§

Unidentified

Chemical

Viral

Bacterial

Parasitic

No. of outbreaks
Vol. 55 / SS-12 Surveillance Summaries 43

Reports for the other four WBDOs did not note a suspected etiologic agent.

Deficiencies

Thirty-three deficiencies were cited in the 30 drinking

water-associated WBDOs. Fourteen (42.4%) deficiencies

involved the source water, treatment facility, or distribution system (SWTD); 17 (51.5%) deficiencies occurred at

points not under the jurisdiction of a water utility or at the

point of use (NWU/POU); and two (6.1%) were unknown

deficiencies (Figure 7; Table 14).

Deficiencies 1-4: Contamination of Water

at/in the Water Source, Treatment

Facility, or Distribution System

Water-quality data. Water-quality data (e.g.,

data regarding the presence of coliform bacteria,

pathogens, or chemical/toxin contaminants; or

data regarding levels of disinfectants, such as chlorine) were available for all 11 WBDOs given a

deficiency classification of 1-4. Bacterial waterquality data were available for the eight WBDOs

with confirmed infectious etiologies, and positive total or fecal coliform results from the implicated water were reported for seven (87.5%). The

implicated water was tested for specific pathogens in two (25.0%) of the eight WBDOs with

confirmed infectious etiologies. However, a pathogen was isolated from water in only one of these

outbreaks; in this mixed-agent outbreak, the

implicated water tested positive for Cryptosporidium

spp., but the other three implicated infectious agents

(C. lari, C. jejuni, and H. canadensis) were not recovered

from the water samples.

Two (18.2%) of the 11 WBDOs with water-quality data

were attributed to chemical/toxin poisoning. In both

WBDOs, sodium hydroxide was the implicated agent and

the water had a high pH level. One (9.1%) of the 11 outbreaks did not have an etiologic agent identified. However,

the implicated water tested positive for both total and fecal

coliforms.

Water systems. Four (36.4%) of 11 WBDOs with deficiencies 1-4 involved community water systems, four

(36.4%) involved noncommunity water systems, two

(18.2%) involved individual water systems, and one (9.1%)

involved both noncommunity and individual water systems

(Tables 8, 10, and 12; Figure 6). Among the four outbreaks

involving community water systems, two (50.0%) were

associated with a treatment deficiency, and two (50.0%)

were associated with problems with the water distribution

system or water storage. Among the four outbreaks involving noncommunity water systems, one (25.0%) was associated with contaminated untreated ground water intended

for drinking; one (25.0%) was associated with a treatment

deficiency; one (25.0%) was associated with a deficiency

in the water distribution system; and one was associated

with both a treatment and a distribution system deficiency.

Among the two outbreaks involving individual water systems, one (50.0%) was associated with contaminated

untreated surface water intended for drinking; and one

(50.0%) was associated with both contaminated untreated

ground water intended for drinking and deficiencies in the

water distribution system. The single outbreak involving

FIGURE 4. Number* of waterborne-disease outbreaks

associated with drinking water, by etiologic agent and month

— United States, 2003–2004

* n = 30.

†Unidentified etiology includes suspected etiologies not confirmed during

the outbreak investigation.

0

2

4

6

8

10

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

Chemical/Toxin

spp.

Infectious (other than spp.)

Unidentified

Legionella

Legionella †

Month

No. of outbreaks

FIGURE 5. Percentage of waterborne-disease outbreaks (WBDOs)

associated with drinking water, by illness and etiology — United States,

2003–2004

* One of the WBDOs had two predominant illnesses: acute respiratory illness and

gastroenteritis.

† All acute respiratory illness was attributed to Legionella spp. § All dermatitis was attributed to chemicals/toxins.

¶ Including one Legionella spp. outbreak that involved both acute respiratory and

gastrointestinal illnesses.

** Each outbreak involves more than one etiologic agent.

All illness (n = 31)*

Acute

Gastroenteritis only (n = 21)*

Dermatitis

6.5%

§

Gastroenteritis

67.7%

Bacteria

28.6%

¶

Chemicals/

Toxins

28.6%

Viruses

4.8%

Unidentified

23.8%

Mixed agents**

9.5%

Parasites

4.8%

respiratory

25.8%

†
44 MMWR December 22, 2006

TABLE 9. Number of waterborne-disease outbreaks (WBDOs) associated with drinking water (n = eight),* by etiologic agent and

water source — United States, 2003–2004

Water source

Ground water Surface water Unknown Mixed source Total

Etiologic agent WBDOs Cases WBDOs Cases WBDOs Cases WBDOs Cases WBDOs Cases

Bacteria 3 200 1 57 0 0 0 0 4 257

Campylobacter spp. 2 130 0 0 0 0 0 0 2 130

C. jejuni and Shigella spp. 0 0 1 57 0 0 0 0 1 57

Salmonella typhimurium 1 70 0 0 0 0 0 0 1 70

Chemicals/Toxins 2 6 0 0 0 0 0 0 2 6

Sodium hydroxide 2 6 0 0 0 0 0 0 2 6

Mixed agents† 1 1,450 0 0 0 0 0 0 1 1,450

C. jejuni, norovirus, and Giardia intestinalis 1 1,450 0 0 0 0 0 0 1 1,450

Unidentified 1 174 0 0 0 0 0 0 1 174

Unidentified 1 174 0 0 0 0 0 0 1 174

Total 7 1,830 1 57 0 0 0 0 8 1,887

Percentage (88) (97) (13) (3) 0 0 0 0 (100) (100)

* WBDOs with deficiencies 1–3 (i.e., surface water contamination, ground water contamination, and water treatment deficiency) were used for

analysis.

†Multiple etiologic agent types (e.g., bacteria, parasite, virus, and/or chemical/toxin) identified.

TABLE 8. Number of waterborne-disease outbreaks (WBDOs) associated with drinking water (n = 11),* by etiologic agent and type of

water system — United States, 2003–2004

Type of water system†

Community Noncommunity Individual§ Mixed system Total

Etiologic agent WBDOs Cases WBDOs Cases WBDOs Cases WBDOs Cases WBDOs Cases

Bacteria 1 34 2 90 2 167 0 0 5 291

Campylobacter spp. 1 34 1 20 1 110 0 0 3 164

C. jejuni and Shigella spp. 0 0 0 0 1 57 0 0 1 57

Salmonella typhimurium 0 0 1 70 0 0 0 0 1 70

Parasites 0 0 1 11 0 0 0 0 1 11

Giardia intestinalis 0 0 1 11 0 0 0 0 1 11

Chemicals/Toxins 2 6 0 0 0 0 0 0 2 6

Sodium hydroxide 2 6 0 0 0 0 0 0 2 6

Mixed agents¶ 1 82 0 0 0 0 1 1,450 2 1,532

C. jejuni, C. lani, Cryptosporidium spp., 1 82 0 0 0 0 0 0 1 82

and Helicobacter canadensis

C. jejuni, norovirus, and G. intestinalis 0 0 0 0 0 0 1** 1,450 1 1,450

Unidentified 0 0 1 174 0 0 0 0 1 174

Unidentified 0 0 1 174 0 0 0 0 1 174

Total 4 122 4 275 2 167 1 1,450 11 2,014

Percentage (36) (6) (36) (14) (18) (8) (9) (72) (100) (100)

* WBDOs with deficiencies 1–4 (i.e., surface water contamination, ground water contamination, water treatment deficiency, and distribution system

contamination) 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 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.

§ Excludes commercially bottled water, therefore not comparable to previous summaries.

¶ Multiple etiologic agent types (e.g., bacteria, parasite, virus, and/or chemical/toxin) identified.

** Noncommunity and individual water systems.
Vol. 55 / SS-12 Surveillance Summaries 45

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, 2003–2004

Water source

Ground water Surface water Unknown Mixed system Total

Type of deficiency No. (%) No. (%) No. (%) No. (%) No. (%)

1: Untreated surface water intended for drinking 0 (0) 1 (100.0) 0 (0) 0 (0) 1 (12.5)

2: Untreated ground water intended for drinking 3 (42.9) 0 (0) 0 (0) 0 (0) 3 (37.5)

3: Treatment deficiency 4 (57.1) 0 (0) 0 (0) 0 (0) 4 (50.0)

Total 7 (100.0) 1 (100.0) 0 (0) 0 (0) 8 (100.0)

* WBDOs with deficiencies 1–3 (i.e., surface water contamination, ground water contamination, and water treatment deficiency) were used for

analysis.

†Each of these WBDOs is associated with a single deficiency.

TABLE 10. Number and percentage of waterborne-disease outbreaks (WBDOs) associated with drinking water (n = 11),* by type of

deficiency (n = 14)† and type of water system — United States, 2003–2004

Type of water system§

Community Noncommunity Individual¶ Mixed system Total

Type of deficiency No. (%) No. (%) No. (%) No. (%) No. (%)

1: Untreated surface water intended for drinking 0 (0) 0 (0) 1 (33.3) 0 (0) 1 (7.1)

2: Untreated ground water intended for drinking 0 (0) 1 (20.0) 1 (33.3) 1** (50.0) 3 (21.4)

3: Treatment deficiency 2 (50.0) 2 (40.0) 0 (0) 0 (0) 4 (28.6)

4: Distribution system deficiency, including storage 2 (50.0) 2 (40.0) 1 (33.3) 1** (50.0) 6 (42.9)

Total 4 (100.0) 5 (100.0) 3 (100.0) 2 (100.0) 14 (100.0)

* WBDOs with deficiencies 1–4 (i.e., surface water contamination, ground water contamination, water treatment deficiency, and distribution system

contamination) were used for analysis.

† Some WBDOs have multiple deficiencies that are tabulated separately. This table reports 14 deficiencies from 11 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 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.

¶ Excludes commercially bottled water, therefore, not comparable to previous summaries.

** Noncommunity and individual water systems.

TABLE 12. Number and percentage of waterborne-disease outbreaks (WBDOs) associated with drinking water (n = 11),* by predominant

illness and type of water system — United States, 2003–2004

Type of water system†

Predominant Community Noncommunity Individual§ Mixed system Total

illness WBDOs Cases (%) WBDOs Cases (%) WBDOs Cases (%) WBDOs Cases (%) WBDOs Cases (%)

Acute respiratory 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0)

Dermatitis 2 6 (4.9) 0 0 (0) 0 0 (0) 0 0 (0) 2 6 (0.3)

Gastroenteritis 2 116 (95.1) 4 275 (100.0) 2 167 (100.0) 1¶ 1,450 (100.0) 9 2,008 (99.7)

Total 4 122 (100.0) 4 275 (100.0) 2 167 (100.0) 1 1,450 (100.0) 11 2,014 (100.0)

* WBDOs with deficiencies 1–4 (i.e., surface water contamination, ground water contamination, water treatment deficiency, and distribution system

contamination) 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 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.

§Excludes commercially bottled water, therefore, not comparable to previous summaries.

¶Noncommunity and individual water systems.
46 MMWR December 22, 2006

both noncommunity and individual water systems was

associated with both contaminated untreated ground

water intended for drinking and deficiencies in the water

distribution system.

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 spring-fed pond. Among

the seven outbreaks related to ground water sources, three

(42.9%) were associated with consumption of untreated

ground water, and four (57.1%) were associated with treatment deficiencies (Tables 9, 11, and 13; Figure 6).

Deficiencies 5A, 6-11, and 99B:

Contamination of Water at Points

Not Under the Jurisdiction of a Water

Utility or at the Point of Use

Water-quality data. Water-quality data indicating a problem with the water were available for 16 (94.1%) of 17

WBDOs with an NWU/POU deficiency. Among the nine

WBDOs with an infectious etiology, eight (88.9%) were

associated with Legionella spp., and one (11.1%) was associated with norovirus (Pennsylvania, January 2004).

Legionella spp. were isolated from the implicated water

sampled in all of the Legionella outbreaks. The implicated

water in the norovirus outbreak tested positive

for fecal coliforms.

Water-quality data were provided with the

reports from all six WBDOs with chemical etiologies. In all six WBDOs, the contaminants causing the WBDO were recovered from the

implicated water: copper in three WBDOs (Minnesota, June and November 2003; and South

Carolina, July 2004); bromate and other by-products of disinfection in one WBDO (Florida,

November 2003); a multiple-chemical cleaning

product in one WBDO (Maine, December

2003); and gasoline by-products in one WBDO

(Florida, October 2004). In the latter, the mechanism by which gasoline by-products got into the

commercially bottled water was unknown, and

this WBDO was given a deficiency of 99B. This

WBDO is included with the other NWU/POU

WBDOs for analysis purposes because commercially bottled water was involved.

Water-quality data also were provided with the

reports from two WBDOs with unidentified etiologies. In one outbreak, the implicated water

tested positive for total coliforms. In the other

outbreak, the implicated water was tested specifically for norovirus, but it was not isolated.

FIGURE 6. Percentage of waterborne-disease outbreaks (WBDOs)

associated with drinking water, by etiologic agent, water system, and

water source — United States, 2003–2004

* 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 previous summaries.

** Noncommunity and individual systems.

†† Deficiencies 1–3. See Table 11.

Etiologic agent (n = 30) Water system (n = 11)

Unidentified

16.7%

§¶

Bacteria

16.7%

†

Mixed agents*

6.7% Viruses

3.3%

Parasites

3.3%

Chemicals/

Toxins

26.7%

Mixed

System**

9.1%

Community

36.4%

Noncommunity

36.4%

Legionella spp.

26.7%

Individual

18.2%

¶

Water source (n = eight)

Surface water

12.5%

Ground water

87.5%

††

TABLE 13. Number and percentage of waterborne-disease outbreaks (WBDOs) associated with drinking water (n = eight),* by

predominant illness and water source — United States, 2003–2004

Water source

Predominant Ground water Surface water Unknown Mixed source Total

illness WBDOs Cases (%) WBDOs Cases (%) WBDOs Cases (%) WBDOs Cases (%) WBDOs Cases (%)

Acute respiratory 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0)

Dermatitis 2 6 (0.3) 0 0 (0) 0 0 (0) 0 0 (0) 2 6 (0.3)

Gastroenteritis 5 1,824 (99.7) 1 57 (100.0) 0 0 (0) 0 0 (0) 6 1,881 (99.7)

Total 7 1,830 (100.0) 1 57 (100.0) 0 0 (0) 0 0 (0) 8 1,887 (100.0)

* WBDOs with deficiencies 1–3 (i.e., surface water contamination, ground water contamination, and water treatment deficiency) were used for

analysis.
Vol. 55 / SS-12 Surveillance Summaries 47

Deficiency 5A: Legionella in water intended for drinking. All eight of the drinking water-associated Legionella

WBDOs occurred in large buildings or in institutional settings and were related to the multiplication of Legionella

spp. in the plumbing. Among the 27 cases attributed to

these Legionella outbreaks, one case was reported to have

symptoms consistent with PF. The majority of cases of

legionellosis were diagnosed by urinary antigen testing, which

is specific for L. pneumophila serogroup 1 (30).

Deficiencies 6-11. Of the eight WBDOs associated with

deficiencies 6-11, three (37.5%) were associated with drink

mix/soda machine deficiencies resulting in copper

intoxication; three (37.5%) were associated with commercially bottled water; one (12.5%) was associated with a

cross-connection in the plumbing inside a building; and

one (12.5%) was associated with point-of-use contamination of a communal water jug at a worksite. All of these

WBDOs have been described (Appendix B).

Deficiency 99A: Unknown/

Insufficient Information

Concerning Contamination

of Water Intended for

Drinking Tap Water

The deficiencies involved in two (6.7%) of

the 30 WBDOs could not be identified

because of insufficient information or

unknown cause of contamination. Water

samples from both of these noncommunity

water systems and tap-water–associated

WBDOs tested positive for E. coli and total

coliforms, but etiologic agents were not identified. One outbreak involved ground water

(i.e., well water), and one involved tap water

from an unknown water source. However,

because the mechanism of contamination was

unknown and the point of contamination

might not have been under the jurisdiction of

a water utility, these two WBDOs are analyzed separately from the SWTD and NWU/

POU deficiencies.

Waterborne Disease

and Outbreaks Associated

with Water Not Intended

for Drinking and Water

of Unknown Intent

Six WBDOs were associated with either WNID (n = three)

or WUI (n = three) (Table 6). More WNID/WUI outbreaks

were reported for 2003–2004 (n = six) than during 2001–

2002 (n = one). The six WNID/WUI outbreaks caused illness among approximately 36 persons and resulted in four

deaths. One (16.7%) WNID/WUI outbreak involved AGI,

and five (83.3%) involved ARI. Two (33.3%) of the six

WNID/WUI outbreaks were categorized as a strength of evidence Class I ranking; one (16.7%) was ranked as Class III;

and three (50.0%) were ranked as Class IV.

Etiologic Agents

Five (83.3%) of the six WNID/WUI outbreaks were

attributed to L. pneumophila serogroup 1, affected 26 persons, and resulted in four deaths. Fifteen of the cases were

associated with LD, and 11 were associated with PF. The

other WNID/WUI outbreak was attributed to E. coli

O157:H7; 10 persons were reported ill.

FIGURE 7. Percentage of waterborne-disease outbreaks (WBDOs)

associated with drinking water, by deficiency* — United States, 2003–2004

* A total of 30 WBDOs but 33 deficiencies.

† Deficiency 99A. See Table 14.

§ Deficiencies 1–4. See Table 14.

¶ Deficiencies 5A, 6–11, 99B. See Table 14.

** Two WBDOs, one with contamination during bottling and one with unknown location or

mechanism of contamination.

All deficiencies (n = 33)*

Unknown

6.1% (2)†

Source water, treatment

facility, or distribution

system (SWTD)

42.4% (14)

§

No water utility

jurisdiction or at

point of use

(NWU/POU)

51.5% (17)

¶

SWTD NWU/POU

Untreated surface water

7.1%

Untreated

ground water

21.4%

Treatment deficiency

28.6%

Distribution

system

42.9%

Commercially

bottled water**

11.8%

Equipment distributing water

(e.g., drink-mix machine)

17.6%

Contamination

at point of use

11.8%

Legionella spp.

in drinking

water system

47.1%

Plumbing

system

5.9%

Storage

5.9%
48 MMWR December 22, 2006

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

The six WNID/WUI outbreaks each had one known

deficiency: five (83.3%) involved Legionella spp. in the water

system (deficiencies 5B and 5C), and one (16.7%) involved

WNID unrelated to Legionella (deficiency 12). Two

(40.0%) of the five Legionella outbeaks involved WNID

(deficiency 5B). In these outbreaks, the aerosolized water

from cooling towers was tested and identified as the source

of Legionella spp. Three Legionella outbreaks (60.0%)

involved WUI (deficiency 5C). In these outbreaks, environmental water testing failed to determine the source of

Legionella spp. The one outbreak unrelated to Legionella

involved E. coli O157:H7 infection after exposure to sewage from a broken septic line at a camp. Campers might

have been exposed in a wash house in which a septic backup occurred or might have been exposed to surface sewage

seepage near the housing area. Campers were observed playing in a wet area near the sewage seepage. No water testing

was performed in this outbreak. However, soil from the

area of the sewage leakage tested negative for the pathogen.

Previously Unreported Outbreaks

Reports of nine previously unreported drinking waterassociated WBDOs that occurred during 1982–2002 were

received for this surveillance period (Table 7). An outbreak

of diarrheal illness occurred among six attendants of a graduation party (New York, July 2002); two had laboratoryconfirmed E. coli O157:H7 infections. This pathogen was

isolated from a private well that provided drinking water

and matched the two laboratory-confirmed cases by pulsedfield gel electrophoresis pattern. The well water supply was

reportedly not disinfected.

TABLE 14. Waterborne-disease and outbreaks associated with drinking water (n = 30), by deficiency (n = 33)* — United States,

2003–2004

Deficiency No.

Contamination of water at/in the water source, treatment facility, or distribution system (SWTD)† 14

1: Untreated surface water intended for drinking 1

2: Untreated ground water intended for drinking 3

3: Treatment deficiency 4

4: Distribution system deficiency, including storage 6

Contamination of water at points not under the jurisdiction of a water utility or at the point of use (NWU/POU)§ 16

5: Legionella spp. in water system

A: Water intended for drinking 8

B: Water not intended for drinking (excluding recreational water) 0

C: Water of unknown intent 0

6: Plumbing system deficiency after the water meter or property line 1

7: Deficiency in building/home-specific water treatment after the water meter or property line 0

8: Deficiency or contamination of equipment/devices using or distributing water 3

9: Contamination during commercial bottling 1

10: Contamination during shipping, hauling, or storage

A: Water intended for drinking – Tap water 0

B: Water intended for drinking – Commercially bottled water 1

11: Contamination at point of use

A: Tap 0

B: Hose 0

C: Commercially bottled water 1

D: Container, bottle, or pitcher 1

E: Unknown 0

Unknown/Insufficient Information 3

99: Unknown/Insufficient information

A: Water intended for drinking – Tap water 2

B: Water intended for drinking – Commercially bottled water 1

C: Water not intended for drinking (excluding recreational water) 0

D: Water of unknown intent 0

Total no. of deficiencies* 33

* More than one deficiency might have been identified during the investigation of a single waterborne disease or outbreak.

†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.

§Contamination of drinking water and deficiencies occurring after the water meter or outside the jurisdiction of a water utility (e.g., in a service line

leading to a house or building, in the plumbing inside a house or building, during shipping or hauling, during storage other than in the distribution

system, at point of use).
Vol. 55 / SS-12 Surveillance Summaries 49

An outbreak of gastroenteritis occurred among 15 students on a class trip (New York, May 1984). During the

trip, 15 (30.6%) of 49 students became ill and experienced nausea and vomiting within 1–2 hours of eating at a

restaurant. The ill students had ingested soda from a soda

fountain that was described as having a metallic taste.

Samples from the soda fountain machine were analyzed for

copper, iron, and other metals and were within the normal

range. However, testing of urine samples collected 2 days

after illness onset demonstrated elevated levels of copper in

some students’ urine samples. Heavy use of fire hydrants

nearby caused pressure problems in the community water

main while students were being served at the restaurant.

These pressure fluctuations might have stirred up sediment

in the distribution system, resulting in excess copper

being delivered to the restaurant water supply.

During April 2002, an outbreak of gastroenteritis in 59

persons occurred in Palau. Entamoeba histolytica was isolated from nine (30.0%) of 30 stool specimens. All ill persons reported consuming untreated drinking water from

the same portable water catchment tank that collected

water from a stream. Water sampled from the tank tested

positive for total and fecal coliform bacteria.

Three outbreaks of gastroenteritis (New York, May 1982,

August 1995, and August 1996) involved unidentified etiologic agents. During the 1982 outbreak, drinking water at

a restaurant was linked to illness. Samples of water and ice

were negative for pathogens, but the raw well water tested

positive for fecal coliform bacteria. In addition, although

the well water received ultraviolet light treatment before

entering the restaurant plumbing system, fecal and total

coliforms were found in water samples after treatment. The

1995 outbreak report implicated water and ice served at a

hotel restaurant. An untreated well was the source of drinking water and water used to make ice. Water samples from

the kitchen faucet were positive for both total coliforms

and E. coli. On the basis of the incubation period, symptoms, and duration of illness, norovirus was suspected.

Investigators speculated that the well water might have been

contaminated or that an ill person might have contaminated the ice after production. During the 1996 outbreak

among campers, a viral etiology was suspected based on

incubation period, symptoms, and duration of illness. The

source of illness was unconfirmed, but a fecally contaminated unchlorinated water supply (i.e., well water) was

suspected. Water samples from the untreated well tested

positive for E. coli. The well had tested positive the previous year for E. coli after a gastroenteritis outbreak.

Reports of two Legionella outbreaks (Maryland and the

U.S. Virgin Islands, November 2002) and one mixed-agent

outbreak (New York, December 2002) were also received

for this surveillance period. These WBDOs have been

described (Appendix B).

Surveillance Reports Not Classified

as Waterborne Disease and Outbreaks

Three surveillance reports potentially implicating drinking water were submitted during 2003–2004 but had

insufficient epidemiologic or laboratory evidence to warrant inclusion in this report as WBDOs. One surveillance

report included only one confirmed case of Legionella

infection; the second suspected case was not laboratory confirmed. Regarding the second report, the investigation did

not reveal a common point source of Legionella transmission. However, because of the potential link to drinking

water, a brief description of the third report has been provided. In July 2003, multiple persons attending a family

reunion developed AGI. E. coli O157:H7 was isolated from

the stool of four attendees. Lemonade made with untreated

water was cited, but other common food and water sources

were identified. No epidemiologic studies were conducted.

Discussion

Considerations Regarding Reported

Results

WBDOSS provides information concerning epidemiologic

and etiologic trends in outbreaks related to drinking water.

However, not all outbreaks are recognized, investigated, or

reported to CDC, and studies have not been conducted that

assess the sensitivity of this system. Furthermore, outbreaks

occurring in national parks, tribal lands, or military bases

might not be reported to state or local authorities. For these

reasons, the true incidence of WBDOs is probably greater

than is reflected in surveillance system data. Multiple factors influence whether WBDOs are recognized and investigated by local or state public health agencies, including

public awareness of the outbreak, availability of laboratory

testing, requirements for reporting diseases, and resources

available to local and state health departments for surveillance and investigation of probable outbreaks. In addition,

because differences in the capacity of local and state public

health agencies and laboratories to detect WBDOs might

result in reporting and surveillance bias, the states with

the majority of outbreaks reported for this period might

not be the states in which the majority of outbreaks actu-
50 MMWR December 22, 2006

ally occurred. An increase or a 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 practices. As with any passive surveillance system, the accuracy of the data depends substantially on the

reporting agencies (i.e., state, local, and territorial health

departments). Therefore, independent of the recognition

or investigation of a given outbreak, reporting bias also can

influence the final data.

The outbreaks most likely to be recognized and investigated are those involving acute illness characterized by short

incubation periods, serious illness or symptoms requiring

medical treatment, or recognized etiologies for which laboratory methods have become more sensitive or widely available. Increased reporting frequently occurs as etiologies

become better recognized, water system deficiencies are

identified, and state surveillance activities and laboratory

capabilities increase (31–33). Consequently, recommendations for improving WBDO investigations include enhancing surveillance activities, increasing laboratory support for

clinical specimen and water sample testing, and assessing

sources of potential bias (34–36).

The identification of WBDO etiologic agents depends

on multiple factors. Investigators must recognize the

WBDO in a timely manner so that appropriate clinical

specimens and environmental samples can be collected.

Collection of water samples further depends on local and

state statutory requirements and the availability of investigators. Methods for concentrating large volumes of water

for testing are being developed and disseminated to multiple sites in the United States as standard protocols (37).

The laboratories involved must have the capacity to concentrate large volumes of water for testing, in addition to

the ability to test for the organism, chemical, or toxin in

the clinical specimens and environmental samples. For

example, routine testing of stool specimens at laboratories

includes tests for the presence of enteric bacterial pathogens and also might include ova and parasite examination.

However, testing for viral agents is rarely conducted,

although norovirus testing is now being performed more

commonly. In addition, clinicians and public health officials must know the correct tests to order. For example,

testing for Cryptosporidium spp., one of the most commonly

reported waterborne pathogens, is frequently not included

in standard ova and parasite examinations and therefore

must be specifically requested (38).

One key limitation of the data collected by the WBDOSS

is that the information pertains only to outbreaks of waterborne illness and not to endemic waterborne illness. The

epidemiologic trends and water-quality concerns observed

in outbreaks might not necessarily reflect or correspond

with trends associated with endemic waterborne illness. In

response to the Congressional Safe Drinking Water Act

Amendments of 1996, in 2005, EPA and CDC completed

a series of epidemiologic studies and a national workshop

designed 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 number of

endemic waterborne AGI cases associated with public drinking water systems in the United States. In particular, the

authors of two reports used current data and made various

assumptions for missing data to derive two different but

overlapping estimates of 1) 4.3–11.7 million annual AGI

cases (confidence interval unknown) (39) and 2) 16.4 million annual AGI cases (range: 5.5–32.8) (40). These estimates should be interpreted with an understanding that

information concerning endemic waterborne-disease risks

is imprecise and uncertain and that substantial data gaps

remain. The wide range in the number of estimated cases

suggests a high level of uncertainty. Nonetheless, workshop

participants agreed that enough data were available for

rough estimates and that these estimates should be made

at this time, with all assumptions and limitations fully

described so the approaches can be evaluated.

These estimates, however, only describe a portion of the

annual incidence of endemic waterborne-disease cases. To

describe the overall incidence, estimates also would need

to include the number of cases of waterborne disease other

than AGI and the number of cases associated with nonpublic

drinking water systems, commercially bottled water, recreational water, WNID, and WUI. If these other types and

sources of waterborne disease were considered, the estimated

number of cases of endemic waterborne disease would be

higher than the figures previously presented in this report.

WBDOs Associated with Water Intended

for Drinking

Etiologic agents

Legionella spp. and chemicals were the most commonly

reported etiologic agents in drinking water-associated

WBDOs. During 2003–2004, eight reported drinking

water-associated WBDOs involved Legionella spp. and comprised 26.7% of the total, which is only the second time

that data concerning Legionella outbreaks have been

included in a Surveillance Summary.
Vol. 55 / SS-12 Surveillance Summaries 51

Chemical/toxin drinking water-associated WBDOs

(n = eight) comprised 26.7% of the total, an increase from

the previous surveillance period and the largest number of

chemical/toxin-related drinking water WBDOs since the

1993–1994 surveillance period. Of the eight chemical/toxin

WBDOs, three (37.5%) resulted from deficiencies related

to drink mix/soda machines, and two (25.0%) resulted

from deficiencies related to recent maintenance work. These

outbreaks stress the importance of proper installation and

maintenance of water systems and equipment. The increased

number of chemical/toxin-related outbreaks also emphasizes the need for increased awareness among the public

and public health officials concerning the role that chemicals and toxins play in WBDOs.

During the 2003–2004 surveillance period, five drinking

water-associated WBDOs involved only bacteria (other than

Legionella spp.), an increase in the number of reported nonLegionella bacterial drinking water outbreaks compared with

the 2001–2002 surveillance period (n = three). The ongoing occurrence of bacterial WBDOs, despite available and

efficacious treatment practices, underscores the continuing

need for protection and treatment of drinking water (41).

In addition, two mixed-agent outbreaks occurred during

the 2003–2004 surveillance period, which included bacteria (one bacterial/parasitic outbreak and one bacterial/

parasitic/viral outbreak). The occurrence of mixed-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, both outbreaks were associated with sewage

contamination of wells, underscoring the importance of

proper waste management and proper drinking water system and waste water system designs.

One viral outbreak involving norovirus was reported for

the 2003–2004 surveillance period (Pennsylvania, January

2004). Norovirus was also one of the etiologic agents identified in one of the mixed-agent outbreaks (Ohio, July 2004)

and was the suspected etiologic agent in one of the outbreaks of unknown etiology (Florida, January 2003), based

on incubation period, symptoms, and duration of illness.

Sewage contamination was suspected in both outbreaks in

which norovirus was identified. Point-of-use contamination

of a water dispenser was a contributing factor in the suspected norovirus outbreak. These three outbreaks represent a decrease in viral drinking water-associated WBDOs

compared with the previous surveillance period (n = five)

and might reflect a true decrease in viral outbreaks, a lack

of outbreak investigation and detection, a lack of viral testing, or a combination of factors.

Compared with the previous surveillance period, the

number of reported parasitic outbreaks decreased for 2003–

2004. Parasites were identified in one single-agent outbreak

(G. intestinalis) and two mixed-agent outbreaks

(Cryptosporidium spp. and G. intestinalis). All three outbreaks were associated with distribution system deficiencies, but only one also was associated with the use of

untreated source water (ground water under the influence

of surface water in Ohio, July 2004). No parasitic outbreaks

were associated with surface water systems. Both surface

water systems and 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 etiologic agent was unidentified in five (16.7%) of

the 30 drinking water-associated WBDOs reported during

2003–2004 (Figure 6). This finding is 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. Five drinking water-associated

outbreaks of unknown etiology occurred during 1997–

1998, but this number represented 29.4% of the reported

non-Legionella outbreaks. This decrease probably reflects

the improved diagnostic capability of laboratories and better outbreak investigations, resulting in more rapid and more

appropriate specimen collection.

Deficiencies 1–4: Contamination of Water

at/in the Water Source, Treatment Facility,

or Distribution System

In general, EPA regulates the public drinking water supplies from the source water up to the water meter (or

before the property line if the distribution system is not

metered). This segment of the drinking water supply system is associated with deficiencies 1–4: 1) consumption of

untreated surface water intended for drinking, 2) consumption of ground water intended for drinking, 3) treatment

deficiencies, and 4) distribution system deficiencies before

the water meter or property line. During the 2003–2004

surveillance period, 36.7% of drinking-water related outbreaks (n = 11) and 42.4% of deficiencies (n = 14)

involved deficiencies 1–4. A single WBDO can be associated with more than one deficiency.

Source water. Discussions regarding source water type

only include those WBDOs with deficiencies 1–3 because

distribution system deficiencies (deficiency 4) are not

dependent upon the source water type. Also excluded from

discussion involving source water types are drinking waterassociated WBDOs with unknown or insufficient information (deficiencies 99A) and outbreaks associated with
52 MMWR December 22, 2006

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. One (12.5%) of the eight outbreaks with

deficiencies 1–3 was associated with consumption of

untreated surface water (deficiency 1) from a spring-fed

pond supplying an individual water system (Ohio,

November 2003). This emphasizes the importance of public

awareness that surface water, despite its clarity, is prone to

contamination by pathogens and should not be directly

consumed without first being treated. If water treatment is

not available as part of the water system, treatment can be

provided at the point of use (e.g., filtration, disinfection

by chemicals, or boiling). Manufacturers of point-of-use

treatment devices and the National Sanitation Foundation

(http://www.nsf.org) provide information regarding different devices, including instructions for their use and their

ability to make water safe for human consumption.

The WBDO in Ohio in 2003 is the first outbreak associated with consumption of untreated surface water intended

for drinking (deficiency 1) since 1999 (3). Since the early

1990s, a decrease has occurred in the percentage of reported

WBDOs associated with either untreated or inadequately

treated surface water. This decrease is likely attributed to

increasingly stringent EPA regulations for treatment of surface water. However, outbreaks might still occur, particularly in water systems that are not subject to EPA

regulations.

Ground water. Seven (87.5%) of the eight outbreaks

with deficiencies 1–3 were associated with consumption of

contaminated ground water from wells. This is the smallest number and percentage of ground waterassociated WBDOs with deficiencies 1–3 in the previous

four surveillance periods (1997–1998 through 2003–

2004). Among these seven outbreaks, three (42.9%)

involved consumption of untreated ground water (deficiency

2), and four (57.1%) involved treatment deficiencies associated with contaminated ground water (deficiency 3). The

highest proportion of these outbreaks (n = three [42.9%])

were associated with noncommunity water systems, but

other water system types also were implicated: community

(n = 2), individual (n = one), and mixed noncommunity

and individual (n = one).

The mixed-system outbreak involving noncommunity and

individual water systems was the largest outbreak during

this surveillance period (Ohio, July 2004). The outbreak

occurred on an island in Lake Erie frequented by vacationers. It also was associated with the use of untreated contaminated ground water (deficiency 2) by noncommunity

and individual drinking water systems and cross-connections to the community water distribution system (deficiency 4). The environmental investigation identified sewage-contaminated ground water wells used for drinking

water as the likely source of exposure to the etiologic agents.

Sewage reached the drinking water aquifer because the karst

limestone geology of the island forms an aquifer that is

vulnerable to contamination. Cracks and fractures in the

limestone allow contaminants from upper soil layers to flow

through to ground water sources. The severe soil limitations and the karst geology of the island connect sewage

system effluent, lake water, and precipitation runoff to the

aquifer. In addition to soils and geology, other possible contributing factors include cross-connections in the water

distribution system; an increase in precipitation before the

outbreak; the volume of wastewater flowing to sewage treatment systems during periods of heavy island visitation; the

number, type and maintenance of sewage disposal systems;

and groundwater well construction.

The seven ground water-associated outbreaks indicate that

contaminated ground water that leads to illness is a continuing problem, and efforts should be intensified to identify and remove possible sources of contamination and

provide adequate, continuous treatment for those systems

that need treatment. Wells and springs must be protected

from contamination, even if disinfection is provided,

because ground water can become contaminated with

pathogens that might overwhelm the disinfection process.

EPA requires appropriate treatment, including filtration and

disinfection, for public water systems that use ground

water under the direct influence of surface water (e.g., those

involved in the Ohio outbreak). EPA’s GWR establishes

multiple barriers for protection against pathogen contamination of drinking water derived from ground water sources.

GWR will also establish a targeted strategy to identify

ground water systems at high risk for fecal contamination.

The multiple barrier approach should begin with protection of the wellhead, an assessment of potential sources of

contamination, and periodic sanitary surveys to ensure that

wells remain protected. Periodic monitoring of source

water is necessary to identify water-quality deterioration,

which if discovered, might require mandatory testing. In

addition, continuous water treatment is needed for wells

that are identified as being vulnerable.

Only public water systems will be directly covered by

GWR; therefore, protections offered by GWR will not

extend to individual ground water systems unless they are

regulated by state or local authorities. The quality of water

in wells and springs used by individuals and nonpublic

systems remains a public health concern; approximately

17 million persons in the United States rely on private
Vol. 55 / SS-12 Surveillance Summaries 53

household wells for drinking water each year, and >90,000

new wells are drilled annually throughout the United States

(42). In addition, contamination of a household well is not

only a health concern for the family served by the well but

is also a concern for households and other water systems

that draw from the same aquifer. To safeguard the quality

of well water, homeowners should seek information on

needed protective measures and implement recommended

operation and maintenance guidelines for private well usage.

Homeowners may also choose to protect their own health

by purchasing appropriately designed point-of-use devices

and by following instructions for operating and maintaining these treatment devices. Although EPA does not regulate individual water systems, EPA recommendations for

protecting private wells are available at http://www.epa.gov/

safewater/pwells1.html. Additional efforts should 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 2003–2004, four drinking

water-related WBDOs associated with water treatment

deficiencies were reported. Two outbreaks resulted in burns

after the discharge of sodium hydroxide into the distribution system during well maintenance. The other two outbreaks involved temporary interruptions of disinfection (one

resulting from a broken chlorine pump [Pennsylvania, June

2004] and one resulting from a faulty ultraviolet light watertreatment apparatus [Montana, August 2004]). All four

outbreaks indicate the need for proper equipment handling,

maintenance, and postmaintenance safety checks.

Distribution system. Distribution system deficiencies

make up the largest proportion of the SWTD deficiencies

occurring before the water meter or property line during

this surveillance period. During 2003–2004, six drinking

water-related WBDOs involving distribution system deficiencies occurred. Four (66.7%) of the six WBDOs involved

cross-connections to nonpotable water sources. As the use

of nonpotable water increases in the United States (e.g., for

landscape and agricultural irrigation, toilet flushing,

industrial processing, and power plant cooling), the risk

for cross-connections between potable and nonpotable

water supplies will also probably increase (43). These four

outbreaks demonstrate the importance of identifying and

clearly labeling potable and nonpotable water lines to prevent cross-connections, which can result in illness.

Water systems. Discussions regarding water system types

(i.e., community, noncommunity, and individual) include

drinking water-associated WBDOs with deficiencies 1–4.

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 11 drinking water-associated WBDOs with a deficiency

of 1–4, four (36.4%) were associated with community

water systems, four (36.4%) with noncommunity water

systems, two (18.2%) with individual water systems, and

one (9.1%) with both noncommunity and individual

water systems (Ohio, July 2004). The proportion (27.3%)

of drinking water-related WBDOs associated with unregulated individual water systems (including the Ohio, July

2004 WBDO) is the lowest proportion of outbreaks within

the last three surveillance periods (i.e., 1999–2000, 2001–

2002, and 2003–2004). This decrease in the proportion

of WBDOs associated with individual drinking water systems might reflect a detection bias (given the limited number of persons who are usually affected by these WBDOs),

limited resources available to investigate these outbreaks,

and the limited number of regulations that govern these

systems.

Deficiencies 5A, 6-11, and 99B:

Contamination of Water at Points

Not Under the Jurisdiction of a Water

Utility or at the Point of Use

By creating additional deficiency classifications, a clear

distinction can be made between deficiencies that occur at

points NWU/POU and SWTD. During the 2003–2004

surveillance period, more WBDOs were associated with

NWU/POU (17 [51.5%]) than with SWTD (14 [ 42.4%])

(Figure 7).

Deficiency 5A: Legionella in Water Intended for Drinking. Legionellosis includes two clinically distinct syndromes:

LD, a form of pneumonia, and PF, an influenza-like illness

without pneumonia. When outbreaks of legionellosis

occur in the setting of contaminated drinking water, they

typically manifest as cases of LD rather than PF. Regardless

of the syndrome, all legionellosis outbreaks share the common features of warm stagnant water, usually documented

inadequate biocide concentrations, and aerosolization, which

provides the mechanism for inhalation into the lungs. The

outbreaks of legionellosis described in this report highlights

multiple challenges related to the detection and prevention of legionellosis.

LD, the more severe form of legionellosis, is underdiagnosed because multiple patients with communityacquired pneumonia can be treated empirically with

broad-spectrum antibiotics (44). However, because

Legionella spp. are not transmitted from person-to-person

and are always acquired from an environmental source, even
54 MMWR December 22, 2006

a single case of LD implies the presence of a contaminated

aquatic source to which others can be exposed. Because host

factors, (e.g., underlying lung disease and immunodeficiencies) are essential for the development of disease, the attack

rate during documented LD outbreaks is <5%. Identification of two or more cases of LD in association with a potential source is adequate justification for an investigation.

All of the outbreaks described in this report involved seven

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.

Three outbreaks occurred among persons in residential

settings (i.e., a condominium complex [Maryland, December 2004], an apartment building [New Jersey, June 2004],

and a senior housing center [New Jersey, July 2004]).

Approximately 70% of sporadic cases of residentially

acquired LD occur among persons living in single family

homes (45). However, because persons living in multipleunit settings can be epidemiologically linked to each other,

outbreaks that occur in these settings have a higher potential to be recognized by public health authorities. The

plumbing systems that serve such buildings tend to be colonized with Legionella spp. in multiple locations, which could

increase the risk of LD to other residents of such buildings

(46). Guidelines for reducing the risk for legionellosis associated with building water systems are available (47). Providing these guidelines to managers of large residential

buildings in addition to other settings more commonly

associated with outbreaks of legionellosis might be a useful

practice for local and state public health authorities.

Three outbreaks demonstrate the propensity for Legionella

spp. to colonize potable water systems and cause disease

over prolonged periods. Legionella spp. colonize the biofilm

layer frequently found inside large, complex plumbing systems (48). This biofilm protects Legionella from biocides

and allows the bacteria to amplify to levels sufficient to be

transmitted. One outbreak (Maryland, November 2002)

previously unreported in any Surveillance Summaries was

associated with a health club and resulted in apparent disease transmission during an 8-week period; all ill persons

were men aged >65 years. In 2004, the potable water system of a long-term–care facility, which also had experienced

an outbreak in 2002, was the source of three additional

cases, including one fatality, despite aggressive remediation

after the 2002 outbreak (Pennsylvania, April 2004). Finally,

LD detected among three guests of a hotel led to an epidemiologic and environmental investigation that identified

the potable water system as the likely source (U.S. Virgin

Islands, November 2002). The comparison of strains of

Legionella spp. isolated during this outbreak with strains

recovered from an outbreak at the same hotel that occurred

during 1981–1982 revealed remarkable similarity, suggesting that the same strain had colonized the system continuously (49). In summary, Legionella is a hardy organism that

resists remediation efforts and therefore can colonize the same

potable water system for years or decades. This hotelassociated outbreak also highlights the importance of timely

reporting of individual cases of travel-associated legionellosis,

as was recently recommended in a 2005 CSTE position

statement (http://www.cste.org/PS/2005pdf/final2005/05-

ID-01final.pdf).

Legionella outbreaks represented >25% of all drinking

water-associated WBDOs reported during 2003–2004 and

47.1% of all NWU/POU deficiencies, indicating that

Legionella as a public health threat requires further attention. Concerted action is necessary to maintain systems

according to published guidelines and to detect and respond to

clusters of cases of legionellosis when they occur (47).

Deficiencies 6–11. Deficiencies involving water intended

for drinking that occur at points after the water meter or

the property line include 1) problems with the plumbing;

2) problems with water treatment after the water meter or

property line; 3) problems with equipment/devices that

use or distribute water (e.g., beverages contaminated by

plumbing failures in drink mix/soda machines); 4) contamination of ice or beverages as a result of the use of contaminated water; 5) contamination during commercial

bottling; 6) contamination during shipping, hauling, or

storage; and 7) contamination at the point of use. The latter three deficiencies frequently involve commercially bottled

water. Commercially bottled water is assumed to be a safe

source of drinking water; however, the WBDOs associated

with commercially bottled water reported during 2003–

2004 are examples of the different situations in which contamination can occur. In one WBDO (Florida, November

2003), contamination by disinfection by-products occurred

at the plant during production and bottling, indicating

that the process of disinfection of bottled water must be

closely monitored. In another WBDO (Maine, December

2003), a cleaning product spilled near the bottled water

and leached through the plastic bottle to contaminate the

water, demonstrating that plastic bottles are permeable to

chemicals and therefore commercially bottled water is vulnerable to chemical contamination after production but

before the seal is broken. Proper shipping, hauling, and

storage of commercially bottled water can prevent this route

of contamination. Commercial vendors and the general
Vol. 55 / SS-12 Surveillance Summaries 55

public need to be aware that commercially bottled water

should be stored off the floor and away from any chemical

products. In a third WBDO (Florida, January 2003), a

large container of commercially bottled water from which

multiple persons were served was contaminated at the point

of use after the bottle had been opened, underscoring the

vulnerability of shared bottles or containers and the importance of practicing good hygiene. A similar outbreak

involving a shared container (Michigan, September 2003)

further illustrates this problem; however, this WBDO was

not associated with commercially bottled water.

Three WBDOs were associated with illness attributed to

ingestion of copper from drink mix/soda machines. In two

of these outbreaks (Minnesota, June 2003; South Carolina, July 2004), problems occurred with backflow of highly

acidic, carbonated water from the carbonators back into

the building piping and resulted in copper leaching from

the pipes. The cause of the malfunction in the third WBDO

(Minnesota, November 2003) was less clear and appeared

to be a problem with the internal plumbing of a juice

machine. Proper installation and maintenance of drink mix/

soda machines, with particular attention given to check

valves, are critical.

One WBDO (Pennsylvania, January 2004) involved a

drinking water pipe being inappropriately cross-connected

with a nonpotable water source within a building. This

WBDO illustrates that cross-connections can be problematic, not only within the distribution system, as illustrated

by four outbreaks discussed regarding deficiency 4, but also

within building/home plumbing. Potable and nonpotable

water lines should be clearly labeled, and plumbing systems should be assessed to prevent and ensure that opportunities for cross-connections do not exist. Approved devices

can prevent both the backflow of nonpotable water into

the potable water system from backpressure and

backsiphonage, but the devices must be maintained and

periodically tested (50). The risk for contamination can be

reduced by water utilities 1) being cognizant of the potential for the intrusion of contaminants into the water distribution system during transient low or negative water

pressure, 2) maintaining an effective disinfectant residual

throughout the distribution system, and 3) detecting and

repairing pipeline leaks (51).

Waterborne Disease and Outbreaks

Associated with Water Not Intended

for Drinking

During the 2003–2004 surveillance period, three WBDOs

occurred that were associated with WNID. Two of these

outbreaks were associated with Legionella spp. and involved

water in cooling towers. The remaining WBDO was associated with E. coli O157:H7 and involved a broken septic line

at a camp, which resulted in sewage seepage near the housing area and a septic back-up in a wash house. Whereas

WNID outbreaks are less commonly reported than drinking

water-related WBDOs, these three outbreaks illustrate that,

whether through inhalation or contact, WNID is still associated with disease and requires attention. Broken septic lines,

sewage seepage, and improper sewage disposal are public

health threats because direct contact with sewage and contamination of drinking water can occur from either ground

water or surface water sources. Sewage disposal systems must

be properly sited and maintained. If drinking water contamination is suspected, public health officials should 1)

institute appropriate measures to prevent consumption of

contaminated water (e.g., issuances of boil-water advisories

and recommendations to use commercially bottled water),

2) evaluate the sewage disposal system, and 3) address any

deficiencies that are identified.

Additional Reporting of Historical

Outbreaks

This report discusses information concerning nine previously unreported drinking water outbreaks. Six of these

outbreaks occurred during 1980–2002 in New York State.

Inclusion of the information regarding New York was

facilitated by a CDC-funded pilot project to improve waterborne-disease surveillance and waterborne outbreak investigations in New York. In 2005, CDC initiated the project

in partnership with the New York State Department of

Health (NYSDOH) as part of CDC’s Environmental Health

Specialist Network (EHS-Net). One element of the project

was the hiring of a new full-time employee within the

NYSDOH to coordinate the EHS-Net water pilot project.

Initial efforts of the pilot project were focused on characterizing the reporting system for waterborne disease in New

York State, including reviewing different databases that

might contain information concerning waterborne-disease

outbreaks. Databases maintained by multiple organizations

within NYSDOH and data housed in certain local health

departments were reviewed, which resulted in the verification of nine outbreaks associated with water intended for

drinking during 1980–2002. Three of these outbreaks had

been previously reported to CDC. One outbreak that

occurred in 2002 was reported to CDC along with the

2003–2004 outbreaks. The five remaining outbreaks had

not been reported to CDC.
56 MMWR December 22, 2006

The EHS-Net water pilot project activities indicate that

increased effort and resources, specifically directed at waterborne disease reporting, could result in the identification

of previously unreported historical outbreaks. As the EHSNet water pilot project refines the process for identifying

and investigating current waterborne-disease incidents,

these efforts might result in enhanced reporting of waterborne outbreaks from New York. In addition, the experience of NYSDOH could provide a template for improving

waterborne-disease reporting in other locations.

Conclusion

Data collected as part of the national WBDOSS are used

to describe the epidemiology of waterborne disease in the

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 the public’s health.

Identification of the etiologic agents responsible for these

outbreaks also is critical because new trends might necessitate different interventions and changes in policies and

resource allocations.

Surveillance for waterborne agents and WBDOs occurs

primarily at the local and state levels (including territories

and FAS). Public health authorities at these levels should

be able to detect and recognize drinking water-associated

WBDOs and implement appropriate prevention and control measures. Improved communication among local and

state public health departments, regulatory agencies, and

water utilities would aid the detection and control of

WBDOs. Routine reporting or sharing of water-quality data

within the health department is recommended. Other

means of improving surveillance at the local, state, and federal levels might include the additional review and followup of information gathered through other mechanisms (e.g.,

issuances of boil-water advisories or reports of illness associated with agents thought to be waterborne). CSTE passed

a position statement at the 2006 annual meeting making

waterborne-disease outbreaks, as a unit of reporting,

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 waterborne outbreaks at the state and local

levels. CSTE also asked CDC and EPA to 1) develop training for WBDO investigations for local and state/territorial

public and environmental health workers responsible for

WBDO detection, investigation, and reporting; and 2)

work with CSTE and EPA to develop national WBDO

investigation and surveillance guidelines. The position statement is available at http://www.cste.org/PS/2006pdfs/

PSFINAL2006/06-ID-12FINAL.pdf (Box).

Acknowledgments

The authors thank the following persons for contributions to this

report: state and territorial waterborne-disease surveillance coordinators,

state epidemiologists, environmental health personnel, and state

drinking water administrators; Michael F. Lynch, MD, Ciara E. O’Reilly,

PhD, Claressa Lucas, PhD, Christopher Braden, MD, and Rachel

Woodruff, MPH, Division of Foodborne, Bacterial and Mycotic

Diseases, National Center for Zoonotic, Vector-Borne, and Enteric

Diseases, (proposed), CDC; Matthew J. Arduino, DrPH, Division of

Healthcare Quality Promotion, National Center for Preparedness,

Detection, and Control of Infectious Diseases (proposed), CDC; Mark

Eberhard, PhD, Monica E. Parise, MD, Dennis Juranek, DVM,

Division of Parasitic Diseases, National Center for Zoonotic, VectorBorne, and Enteric Diseases (proposed), CDC; John Sarisky, MPH,

Division of Emergency and Environmental Health Services, National

Center for Environmental Health, CDC; Lorraine Backer, PhD, Division

of Environmental Hazards and Health Effects, National Center for

Environmental Health, CDC.

References

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

FL: CRC Press, Inc.; 1986.

2. CDC. Water-related disease outbreaks annual summary 1978.

Atlanta, GA: US Department of Health and Human Services, Public

Health Services, CDC; May 1980.

3. 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.

4. 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.

5. Environmental Protection Agency. Water programs: national interim

primary drinking water regulations. 40 CFR Part 141. Federal Register 1975;40:59566–74.

6. Pontius FW, Roberson JA. The current regulatory agenda: an update.

Major changes to USEPA’s current regulatory agenda are anticipated

when the SDWA is reauthorized. Journal of the American Water Works

Association 1994;86:54–63.

7. Pontius FW. Implementing the 1996 SDWA amendments. Journal of

the American Water Works Association 1997;89:18–36.

8. 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.

9. 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.

10. 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.
Vol. 55 / SS-12 Surveillance Summaries 57

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. Environmental Protection Agency. National primary drinking water

regulations: 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: ground water rule; proposed rules. 40 CFR Parts 141 and

141. Federal Register 2000;65:30194–274.

20. Environmental Protection Agency. Announcement of the drinking water

contaminant candidate list; notice. Federal Register 1998;63:10274–87.

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

Testing for Parasites

Telephone: 770-488-7775

Division of Parasitic Diseases

National Center for Zoonotic, Vector-borne,

 and Enteric Diseases (proposed)

Coordinating Center for Infectious Diseases, CDC

Testing for Viral Organisms

Telephone: 404-639-3607

Division of Viral Diseases

National Center for Immunization and Respiratory

Diseases (proposed)

Coordinating Center for Infectious Diseases, CDC

State Reporting of Waterborne Disease and Outbreaks

All WBDOs at the local level should be reported to

the state health department.

Telephone: 770-488-7775

Fax: 770-488-7761

Division of Parasitic Diseases

National Center for Zoonotic, Vector-Borne,

and Enteric Diseases (proposed)

Coordinating Center for Infectious Diseases, CDC

CDC Reporting Form CDC 52.12 (rev.01/2003)

Internet: http://www.cdc.gov/healthyswimming/

downloads/cdc_5212_waterborne.pdf

State and territorial health departments may request

epidemiologic assistance and laboratory testing from CDC

to investigate WBDOs. CDC and the U.S. Environmental Protection Agency (EPA) may be consulted regarding

engineering and environmental aspects of drinking-water

treatment during and after outbreaks and collection of

large-volume water samples to identify pathogens that

require special protocols for their recovery. EPA and the

U.S. Geological Survey may be consulted for assistance

with hydrogeologic investigations of outbreaks where

untreated ground water is suspected.

Environmental Protection Agency Safe Drinking

Water Hotline

Telephone: 800-426-4791

E-mail: hotline-sdwa@epa.gov

Internet: http://www.epa.gov/safewater

Testing for Bacterial Enteric Organisms

Telephone: 404-639-1798

Division of Foodborne, Bacterial and Mycotic

Diseases

National Center for Zoonotic, Vector-borne,

 and Enteric Diseases (proposed)

Coordinating Center for Infectious Diseases, CDC

Information or Testing for Legionella

Telephone: 404-639-2215

Internet: http://www.cdc.gov/legionella

Division of Bacterial Diseases

National Center for Immunization and Respiratory

Diseases (proposed)

Coordinating Center for Infectious Diseases, CDC
58 MMWR December 22, 2006

21. Environmental Protection Agency. Drinking water contaminant candidate list 2; final notice. Federal Register 2005;70:9071–7.

22. Environmental Protection Agency. Unregulated contaminant monitoring regulation for public water systems; analytical method for list

2 contaminants; clarifications to the unregulated contaminant monitoring regulation. 40 CFR Part 141. Federal Register 2001;66:2273–308.

23. 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.

24. 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.

25. 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.

26. Environmental Protection Agency. Public drinking water systems: facts

and figures. February 28, 2006. Available at http://www.epa.gov/

safewater/pws/factoids.html.

27. Environmental Protection Agency. Private drinking water wells. February 21, 2006. Available at http://www.epa.gov/safewater/privatewells/

index2.html.

28. Blackburn B, 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.

29. Yoder JS, Blackburn BG, Craun GF, et al. Surveillance for waterbornedisease outbreaks associated with recreational water—United States,

2001–2002. In: Surveillance Summaries, October 22, 2004. MMWR

2004;53(No. SS-8):1–21.

30. 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.

31. Frost FJ, Calderon RL, Craun GF. Waterborne disease surveillance:

findings of a survey of state and territorial epidemiology programs.

J Environmental Health 1995;58:6–11.

32. Frost FJ, Craun GF, Calderon RL. Waterborne disease surveillance.

Journal of the American Water Works Association 1996;88:66–75.

33. 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.

34. Craun GF, Frost FJ, Calderon RL, et al. Improving waterborne disease

outbreak investigations. Int J Environ Health Res 2001;11:229–43.

35. 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; 2003:25–44.

36. Hunter PR, Waite M, Ronchi E, eds. Drinking water and infectious

disease: establishing the links. Boca Raton, FL: CRC Press; 2003:221.

37. Hill VR, Polaczyk AL, Hahn D, et al. Development of a rapid method

for simultaneous recovery of diverse microbes in drinking water by

ultrafiltration with sodium polyphosphate and surfactants. Applied

and Environmental Microbiology 2005;71:6878–84.

38. Jones JL, Lopez A, Wahlquist SP, Nadle J, Wilson M. Survey of clinical laboratory practices for parasitic diseases. Clin Infect Dis

2004;38(Suppl 3):S198–S202.

39. 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. Journal of Water and Health 2006;4(Suppl 2):71–88.

40. Messner M, Shaw S, Regli S, Rotert K, Blank V, Soller J. An approach

for developing a national estimate of waterborne disease due to drinking water and a national estimate model application. Journal of Water

and Health 2006;4(Suppl 2):201–40.

41. Environmental Protection Agency, Office of Water. The history of

drinking water treatment. Available at http://www.epa.gov/safewater/

consumer/pdf/hist.pdf.

42. 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.

43. Environmental Protection Agency. Guidelines for water reuse. Washington, DC: Environmental Protection Agency; 2004. Publication no.

EPA/625/R-04/108. Available at http://www.epa.gov/ORD/NRMRL/

pubs/625r04108/625r04108.pdf.

44. Bartlett JG. Decline in microbial studies for patients with pulmonary

infections. Clin Infect Dis 2004;39:170–2.

45. Straus WL, Plouffe JF, File TM Jr, et al. Risk factors for domestic acquisition of Legionnaires disease. Arch Intern Med 1996;156:1685–92.

46. Flannery B, Gelling LB, Vugia DJ, et al. Reducing Legionella colonization of water systems with monochloramine. Emerg Infect Dis 2006;

12:588–96.

47. ASHRAE 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.

48. Fields BS, Benson RF, Besser RE. Legionella and Legionnaires’ disease: 25

years of investigation. Clinical Microbiology Reviews 2002;15:506–26.

49. Cowgill KD, Lucas CE, Benson RF, et al. Recurrence of Legionnaires

disease at a hotel in the United States Virgin Islands over a 20-year

period. Clin Infect Dis 2005;40:1205–7.

50. Levy DA, Bens MS, Craun GF, Calderon RL, Herwaldt BL. Surveillance for waterborne-disease outbreaks—United States, 1995–1996.

In: Surveillance Summaries, December 11, 1998. MMWR 1998;

47(No. SS-5):1–34.

51. LeChevallier MW, Gullick RW, Karim MR, Friedman M, Funk JE.

The potential for health risks from intrusion of contaminants into the

distribution system from pressure transients. Journal of Water and

Health 2003;1:3–14.
Vol. 55 / SS-12 Surveillance Summaries 59

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 Backflow occurs when pressure from a customer’s water system (e.g., potentially nonpotable

water) is higher than pressure in the public water system.

backsiphonage Backflow caused by negative or subatmospheric pressure within a water system.

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 water

systems 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 Waterborne disease and outbreaks are classified according 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 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 source

of 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).
60 MMWR December 22, 2006

disinfection by-products Chemicals formed in water by the reaction between organic matter and other waste products and disinfectants.

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.

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 the

water 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 is a strong 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) to

remove 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 As defined by the U.S. Environmental Protection Agency (EPA), any water beneath the

the direct influence surface of the ground with substantial occurrence of insects or other macrooganisms, algae,

of surface water 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

might regularly 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.
Vol. 55 / SS-12 Surveillance Summaries 61

maximum contaminant level The maximum permissible concentration (i.e., level) of a contaminant in water supplied

to any user of a public water system.

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).

mixed-illness outbreak More than one type of illness is reported by >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

water system of the same persons for more than 6 months per year (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 waterborne disease and outbreak (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 for water

not intended for drinking or 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

the Safe 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 may be available as a source of raw water for drinking purposes and/or recreational

use. In some 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, and hotel).

source water Untreated water (i.e., raw water) used to produce drinking water.
62 MMWR December 22, 2006

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

from subsurface or ground water.

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 that is not a community system and that does not regularly

water system serve at least 25 of the same persons over 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, and 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 Water that has not been treated for human consumption in conformance with EPA drinking

for drinking water standards and that is provided for uses other than for drinking.

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.
Vol. 55 / SS-12 Surveillance Summaries 63

May 2003 Washington Campylobacter spp. 110 Attendees of a tent revival experienced gastrointestinal illness. Participants were from British

Columbia, Idaho, Montana, Oregon, and Washington. A case-control study suggested an

association between illness and consumption of farm water. The farm had both domestic and

irrigation wells. Water samples from both wells were positive for fecal coliforms. Leaking valves

and backsiphonage through cross-connections might have contributed to contamination of the

domestic well water.

November 2003 Ohio C. jejuni and Shigella spp. 57 An unlicensed caterer prepared food for several luncheons at her home to be served at a

worksite. Iced tea made from untreated water from a spring-fed pond was associated with

gastrointestinal illness. Tests performed on water from the caterer’s kitchen sink and pitcher

carbon filter were positive for total coliforms and Escherichia coli but negative for

Campylobacter and Shigella.

December 2004 Wisconsin C. jejuni 20 Restaurant patrons experienced gastrointestinal illness. A well supplying water for the

restaurant tested positive for total coliforms and E.coli. The well water was untreated and

taken from a karst aquifer. Years before this outbreak, the restaurant water also tested

positive for coliform bacteria and had been issued with a boil-water advisory.

November 2002 Maryland Legionella pneumophila 3 Health club patrons became ill with laboratory-confirmed Legionnaires’ disease during an

serogroup 1 8-week period. L. pneumophila serogroup 1 was isolated from a locker room shower. No clinical

isolates were available for comparison.

November 2002 Virgin Islands L. pneumophila 3 Three Danish travelers had laboratory-confirmed Legionnaires’ disease after staying at a hotel

serogroup 1 implicated in a Legionnaires’ disease outbreak during 1981–1982. All three cases were reported to

local authorities by the European Surveillance Scheme for Travel-Associated Legionnaires’

disease (http://www.ewgli.org), a surveillance program in place since 1987. Comparison of

environmental strains collected from the hotel suggests that the potable water system was

colonized with the same strain of Legionella for over 20 years. (Source: Cowgill KD, Lucas CE,

Benson RF, et al. Recurrence of Legionnaires’ disease at a hotel in the United States Virgin

Islands over a 20-year period. Clin Infect Dis 2005;40:1205–7.)

October 2003 Maryland L. pneumophila 7 Seven laboratory-confirmed cases were detected among guests of a hotel. This outbreak was

serogroup 1 detected by enhanced surveillance conducted by a single state (Source: CDC. Legionnaires’

disease associated with potable water in a hotel—Ocean City, Maryland, October 2003–

February 2004. MMWR 2005;54:165–8.)

January 2004 New York L. micdadei 2 One definite health-care–associated case and one possible health-care–associated case were

hospitalized at the same facility. Comparison of clinical and environmental isolates of L.

micdadei revealed that they were related.

April 2004 Pennsylvania L. pneumophila 3 (1) Three laboratory-confirmed cases of Legionnaires’ disease were residents of a long-term–care

serogroup 1 facility that was the source of an outbreak in 2002. In that outbreak and this one, L.

pneumophila serogroup 1 was isolated from the facility’s potable water system.

July 2004 Ohio L. pneumophila 2 Two laboratory-confirmed cases of Legionnaires’ disease occurred among workers at a street

serogroup 1 maintenance garage. The source of the cluster was not identified.

September 2004 North Carolina L. pneumophila 7 (3) The presence of laboratory-confirmed cases of Legionnaires’ disease among residents of a

serogroup 1 long-term–care facility suggested that the potable water system of the facility was the source.

However, further investigation revealed that a cooling tower approximately one quarter of a mile

away was the likely source of these cases as well as community-acquired cases.

August 2004 Montana Salmonella typhimurium 70 Restaurant patrons experienced diarrheal illness. Investigators determined that well water

samples were positive for coliform bacteria and the ultraviolet disinfection unit was out of

service. In addition, an existing cross-connection in the distribution system might have

resulted in the backflow of water supplying a poultry pen.

Viruses

January 2004 Pennsylvania Norovirus 70 Visitors to a ski facility experienced gastrointestinal illness after drinking beverages from a

soda fountain that had been cross-connected with a nonpotable water line drawing water from a

pond. The pond water was untreated and tested positive for fecal coliforms. Potential sources

of contamination of the pond water included snow melt and an adjacent septic system.

Appendix B

Descriptions of Selected Waterborne Disease and Outbreaks (WBDOs)

Associated with Drinking Water, Water Not Intended for Drinking,

and Water of Unknown Intent

State/Territory

 in which No. of cases

WBDO date WBDO occurred Etiologic agent (deaths) WBDO description

Bacteria
64 MMWR December 22, 2006

November 2003 Florida Bromate and other 2 Two persons consuming commercially bottled water experienced gastrointestinal illness. The

disinfection by-products water had a chemical odor. Testing of both opened and sealed bottles revealed above standard

levels of bromate and other byproducts of chemical disinfection. This contamination likely

occurred during the bottling process.

December 2003 Maine Cleaning product 2 Two persons consuming commercially bottled water experienced gastrointestinal illness.

Testing indicated contamination of both the water and the outside of the bottles. The bottles

were purchased at the same grocery store. The bottom of one of the boxes containing the

bottles showed evidence of a spill. An investigation into possible contamination revealed that

boxes of commercially bottled water were stored in direct contact with the floor. During the

investigation, a store employee reported that a cleaning product had been spilled near the

boxes of bottled water and that two to three bottles had to be wiped off during the clean up.

June 2003 Minnesota Copper 4 Restaurant patrons had gastrointestinal illness after consuming soda from a fountain machine.

Beverage samples from the machine had copper levels above the acceptable 1.3 parts per

million (ppm). A faulty check valve on the carbonator was found, suggesting that carbon

dioxide was leaking into the water supply, reducing the pH of the water, resulting in copper

leeching from the pipes.

November 2003 Minnesota Copper 5 Restaurant patrons experienced gastrointestinal illness after consuming lemonade from a juice

machine receiving frozen concentrated lemonade and diluting it with water before dispensing.

Copper levels in samples from the machine were elevated (6.4 to 12.8 mg/L). Installation of a

check valve and attachment to a different water supply did not reduce copper levels below the

EPA action level (1.3 mg/L), suggesting internal plumbing problems.

July 2004 South Carolina Copper 7 Restaurant patrons had gastroenteritis after consuming beverages from a soda fountain

machine. Official samples collected from the soda fountain machines were within normal limits

for metals. However, a pooled sample of three left-over beverages consumed by patrons had a

copper level (8.1 mg/L) exceeding EPA standards. Copper levels in two serum specimens and

six urine specimens from ill patrons were within normal limits (dates of specimen collection not

reported). An inspection of the soda fountain machines did not reveal any critical violations.

March 2003 New York Sodium hydroxide 4 Four persons suffered chemical burns after repairs were made on a check valve in the

discharge line of a well supplying a community water system. While the discharge line was

depressurized during maintenance, caustic soda had siphoned into the discharge main. When

the well was placed back into service, approximately 50–100 gallons of 50% sodium hydroxide

flowed into the distribution system. The water utility received complaints of “dirty water” and

“burning sensation” from members of the community following well maintenance. An investigation found that a high pH was responsible.

April 2004 New Jersey Sodium hydroxide 2 One person received a first degree chemical burn while showering and another person suffered

an esophageal chemical burn after consuming water from a community water system. Failure of

a check valve for the sodium hydroxide feed on a well resulted in discharge of this chemical

into the distribution system. The pH meter at the well treatment plant recorded a maximum pH

of 12.5.

Mixed agents

December 2002 New York C. jejuni, Entamoeba spp., 27 Residents and visitors in an apartment complex experienced gastrointestinal illness. A broken

and Giardia spp. sewer line from an on-site sewage disposal system had flooded the basement of the main

building in which a well supplying drinking water for the complex was located. Several inches of

water and sewage covered the well head resulting in fecal contamination of the well water.

Because of its relatively small size, the facility had not been identified or regulated as a

community water supply before the reports of illness.

January 2004 Ohio C. jejuni, C. lari, 82 Workers at a factory experienced gastrointestinal illness. Contamination of the potable

Cryptosporidium spp., and water supply occurred through an open valve connecting the plant’s municipal water supply

Helicobacter canadensis with the coolant line drawing nonpotable water from holding ponds behind the plant. The pond

water was used to cool the plant’s machinery and tested positive for Cryptosporidium spp.

July 2004 Ohio C. jejuni, norovirus, 1,450 Residents and visitors at a resort island in Lake Erie experienced gastrointestinal illness. A

and G. intestinalis number of noncommunity public and private wells tested positive for total coliforms and E. coli,

among other microorganisms (e.g., other bacteria, parasites, and viruses). Investigators

concluded that substantial microbiological contamination of the ground water in the karst

aquifer from multiple land uses was present, such as on-site septic systems, land application

of septage, infiltration of land run-off, and possibly from the direct hydraulic connection with

Lake Erie. Water quality degradation most likely occurred over a long period. Other possible

contributing factors included cross-connections in the water distribution system; an increase in

precipitation before the outbreak; the volume of wastewater flowing to sewage treatment

systems during periods of heavy island visitation; the number, type, and maintenance of

sewage disposal systems; and groundwater well construction.

State/Territory

 in which No. of cases

WBDO date WBDO occurred Etiologic agent (deaths) WBDO description

Chemicals/Toxins
Vol. 55 / SS-12 Surveillance Summaries 65

January 2003 Florida Norovirus suspected 419 Players, coaches, and spectators who attended a volleyball tournament experienced

gastrointestinal illness. The incubation period, clinical presentation, and duration of illness

suggested norovirus as the etiologic agent. During the tournament, numerous opportunities

existed for contact between players. Some also reported touching their refillable water bottles

to the spouts of 5-gallon commercially bottled water containers beside the courts. The only

statistically significant relative risk (RR = 2.24; confidence interval = 1.14–4.41) in a cohort

study among the players was drinking water from these containers. While the water tested

negative for norovirus, contaminated spouts or levers on the containers that the players

depressed to dispense water might have contributed to the spread of illness. Person-to-person

transmission, fomite transmission, and aerosolization of vomitus likely also played roles.

July 2003 Illinois Unidentified 180 Visitors to a water park experienced gastrointestinal illness. Testing of stool samples from eight

persons failed to identify an etiologic agent. An epidemiologic study implicated drinking water at

the park. Chlorinated drinking water was supplied from 13 on-site wells. E. coli was detected in

10 of 29 water samples.

September Michigan Unidentified 4 Construction workers installing sewer lines experienced gastrointestinal illness. Stool cultures

2003 for each ill worker were negative. All ill workers drank from a communal water jug that might

also have been used to wash parts.

June 2004 Pennsylvania Unidentified 174 Attendees of a camp experienced gastrointestinal illness. Testing of stool samples from five

persons failed to identify an etiologic agent. Sometime in the week before the outbreak, a

vehicle damaged a sewer pipe and sewage flowed into a lake. A shallow well supplying drinking

water was located near the edge of this lake. Two days before the onset of the first case, camp staff

discovered that the chlorine pump on this well was broken. Testing of the well water revealed high

coliform levels, suggesting that the well water was under the influence of surface water.

State/Territory

 in which No. of cases

WBDO date WBDO occurred Etiologic agent (deaths) WBDO description

Unidentified
MMWR

The Morbidity and Mortality Weekly Report (MMWR) Series is prepared by the Centers for Disease Control and Prevention (CDC) and is available free of charge

in electronic format. To receive an electronic copy each week, send an e-mail message to listserv@listserv.cdc.gov. The body content should read SUBscribe mmwrtoc. Electronic copy also is available from CDC’s Internet server at http://www.cdc.gov/mmwr or from CDC’s file transfer protocol server at ftp://ftp.cdc.gov/pub/

publications/mmwr. Paper copy subscriptions are available through the Superintendent of Documents, U.S. Government Printing Office, Washington, DC

20402; telephone 202-512-1800.

Data in the weekly MMWR are provisional, based on weekly reports to CDC by state health departments. The reporting week concludes at close of business on

Friday; compiled data on a national basis are officially released to the public on the following Friday. Data are compiled in the National Center for Public Health

Informatics, Division of Integrated Surveillance Systems and Services. Address all inquiries about the MMWR Series, including material to be considered for

publication, to Editor, MMWR Series, Mailstop E-90, CDC, 1600 Clifton Rd., N.E., Atlanta, GA 30333 or to www.mmwrq@cdc.gov.

All material in the MMWR Series is in the public domain and may be used and reprinted without permission; citation as to source, however, is appreciated.

Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services.

References to non-CDC sites on the Internet are provided as a service to MMWR readers and do not constitute or imply endorsement of these organizations or

their programs by CDC or the U.S. Department of Health and Human Services. CDC is not responsible for the content of these sites. URL addresses listed in

MMWR were current as of the date of publication.

✩U.S. Government Printing Office: 2006-523-056/40093 Region IV ISSN: 1546-0738