Food Safety: CDC Is Working to Address Limitations in Several of Its Foodborne Disease Surveillance Systems
Released: 2001-10-09T00:00:00

Letter

Background

Surveillance of foodborne diseases allows public health officials to recognize trends, detect outbreaks, pinpoint the causes of these outbreaks, and develop effective prevention and control measures. Such surveillance presents a complex challenge. Many foods today are imported, prepared and/or eaten outside the home, and widely distributed after processing. As a result, an outbreak of foodborne disease can involve people in different localities, states, and even countries. The number and diversity of foodborne diseases further complicate surveillance. Although many of the more well-known foodborne pathogens are bacteria, such as E. coli O157:H7 and Salmonella, foodborne diseases are caused by a variety of other pathogens, including viruses, parasites, and toxins. Some of these diseases also can be transmitted by nonfood sources, such as through water or through person-to-person contact. Appendix II describes the major foodborne diseases currently under national surveillance.

The surveillance process usually begins when a person with a foodborne disease seeks medical care. To help determine the cause of the patient’s illness, a physician may rely on a laboratory test, which could be performed in the physician’s own office, a hospital, an independent clinical laboratory, or a public health laboratory. If the test shows that the patient is ill with a disease (including a foodborne disease) that must be reported under state law, or if the physician diagnoses the disease without the use of a test, the cases are usually reported to the local health department. Health department staff collect these reports, check them for completeness, contact health-care professionals to obtain missing information or clarify unclear responses, and forward them to state health agencies. Staff resources devoted to disease reporting vary with the overall size and mission of the health department. Because nearly half of local health agencies have jurisdiction over a population of fewer than 25,000, many cannot support a large, specialized staff to work on disease reporting.

The states have principal responsibility for protecting the public’s health and therefore take the lead in conducting surveillance. In state health departments, epidemiologists analyze the data reported and decide when and how to supplement passive reporting with active surveillance methods, conduct outbreak and other disease investigations, and design and evaluate disease prevention and control efforts. They also transmit state data to CDC, providing routine reporting on selected diseases.

Surveillance data are transmitted to CDC both electronically and using paper-based systems. Information about individual cases of disease is reported through two electronic systems. The National Electronic Telecommunications System for Surveillance collects data submitted by epidemiologists about patient demographics and residences, suspected or confirmed diagnoses, and the dates of disease onset. In contrast, the second system, the Public Health Laboratory Information System, collects more definitive data from public health laboratory officials on pathogens identified by laboratory tests. Both systems also offer disease-specific reporting options that states may use to report additional data to CDC. For some surveillance systems, such as the Viral Hepatitis Surveillance Program, data are submitted to CDC both electronically and using paper forms. For other surveillance systems, such as the Foodborne Disease Outbreak Surveillance System, the data are submitted primarily through paper reporting. CDC officials told us they have an ongoing effort to integrate public heath information collected through these and other systems. They estimate this effort will take several years to complete.

Federal participation in the foodborne disease surveillance network focuses on CDC activities—particularly those of the National Center for Infectious Diseases. CDC analyzes the data furnished by states to (1) monitor national health trends, (2) formulate and implement prevention strategies, (3) evaluate state and federal disease prevention efforts, and (4) identify outbreaks that affect multiple jurisdictions, such as more than one state. CDC routinely provides public health officials, medical personnel, and others information on disease trends and analyses of outbreaks.

In fiscal year 2000, CDC’s budget for foodborne disease surveillance through the Food Safety Initiative was $29 million. In order to maximize the effectiveness of its surveillance efforts, CDC works with the Council of State and Territorial Epidemiologists, a professional association of public health epidemiologists from each U.S. state and territory. They are responsible for monitoring trends in health and health problems and devising prevention programs that promote the entire community’s health. The council is currently in its eighth year of a cooperative agreement with the CDC and has approximately 15 separate activities on which they work collaboratively with the CDC. CDC also works with the Association of Public Health Laboratories, which links local, state, national, and global health leaders in order to promote the highest quality laboratory practices worldwide.

However, regardless of the completeness and comprehensiveness of a surveillance system, it can generally detect only a fraction of disease cases—the tip of the iceberg, at best, as shown in figure 1.

Very few people who contract foodborne diseases actually seek treatment, are properly diagnosed, have their diagnoses confirmed through laboratory analysis, and then have their cases reported through the surveillance systems. For example, a recent CDC-sponsored study estimated that 340 million annual episodes of acute diarrheal illness occurred in the United States, but only 7 percent of people who were ill sought treatment. The study further estimated that physicians requested laboratory testing of a stool culture for only 22 percent of those patients who sought treatment, which produced about 6 million test results that could be reported.

Although federal participation in foodborne disease surveillance focuses on CDC activities, two other federal agencies have a key role in the wider arena of food safety and use surveillance information in their programs. USDA’s Food Safety and Inspection Service is responsible for ensuring that meat, poultry, and processed egg products moving in interstate and foreign commerce are safe. This agency primarily carries out its responsibilities through inspections at meat, poultry, and egg processing plants to ensure that these products are safe, wholesome, and accurately labeled. In addition, the Food and Drug Administration in the Department of Health and Human Services is responsible for ensuring that all other domestic and imported food products are safe. Unlike the USDA, the Food and Drug Administration, by and large, conducts post-market surveillance through domestic inspections and testing of products already in commerce to assure that foods are safe and comply with appropriate standards. This is especially true for imported foods where the surveillance program is primarily post-market testing, because the Federal Food, Drug and Cosmetic Act does not provide explicit inspection authority outside the United States. In addition to their other duties, these two agencies work to remove from the market foods that are implicated in foodborne disease outbreaks.

CDC Foodborne Disease Surveillance Systems Provide National Data Needed to Prevent and Control the Spread of Foodborne Disease

CDC conducts surveillance of foodborne diseases through 20 systems. Four of these—the Foodborne Disease Outbreak Surveillance System, FoodNet, PulseNet, and the Surveillance Outbreak Detection Algorithm— focus on foodborne diseases and cover multiple pathogens. The other 16 either collect data about a variety of diseases, only some of which are foodborne, or focus exclusively on a single foodborne disease. Collectively, these systems provide information to detect and control the spread of foodborne disease.

The Foodborne Disease Outbreak Surveillance System collects nationwide information about the occurrence and causes of foodborne outbreaks. This system relies on local health officials to correctly identify, investigate, and report outbreaks to CDC through state public health officials. CDC uses the system to, among other things, compile and periodically report national outbreak data. In 1997, the latest year for which published data are available, states and U. S. territories reported 806 outbreaks to CDC through this system. Furthermore, information from this system can serve as a basis for regulatory and other changes to improve food safety. For example, data from the Foodborne Disease Outbreak Surveillance System has played an important role in documenting the importance of shell eggs as a source of human infection with Salmonella Enteritidis. In response to this data and other reports pointing out the dangers posed by improperly handled eggs, government agencies and the egg industry have taken steps to reduce Salmonella contamination of eggs. These steps include refrigerating eggs during transport from the producer to the consumer, identifying and removing infected laying flocks, diverting eggs from infected flocks to pasteurization facilities, and increasing on-farm quality assurance and sanitation measures. CDC has advised state health departments, hospitals, and nursing homes of specific measures to reduce Salmonella Enteritidis infection, and the USDA tests the breeder flocks that produce egg-laying chickens to ensure that they are free of Salmonella Enteritidis. The Food and Drug Administration has amended its regulations, which now require that all shell eggs in retail establishments be held at a temperature of 45 degrees Fahrenheit or lower and that all egg cartons carry safe-handling instructions to inform consumers about proper storage and cooking of eggs.

FoodNet is a surveillance system operating in nine sites selected by CDC on the basis of their capability to conduct active surveillance and because of their geographic location. FoodNet produces a more stable and accurate national estimate than is otherwise available of the frequency and sources of nine foodborne pathogens, hemolytic uremic syndrome (a serious complication of E. coli O157:H7 infection), Guillain-Barre syndrome (a serious complication of Campylobacter infection), and toxoplasmosis. These improved estimates result from the use of active surveillance and additional studies that are not characteristic of CDC’s other foodborne surveillance systems. Public health departments who participate in FoodNet receive funds from CDC to systematically contact laboratories in their geographical areas and solicit incidence data. In 1999, state officials participating in FoodNet contacted each of the more than 300 clinical labs within the FoodNet areas on a regular basis. FoodNet studies include various “case control” studies, which are used to determine factors, such as food preparation or handling practices, that affect the risk of infection by pathogens covered by the system. The studies also examine the association between infections and specific foods. In addition, public health officials that participate in FoodNet conduct surveys to identify physician and lab practices that may limit the identification of foodborne diseases.

PulseNet is a nationwide network of public health laboratories that perform DNA “fingerprinting” on four types of foodborne bacteria in order to identify and investigate potential outbreaks. The four bacteria fingerprinted by PulseNet—Salmonella, E. coli O157:H7, Listeria, and Shigella—were selected because of their public health importance and the availability of specific “fingerprinting” methods for the pathogens. These four bacteria are either common or have severe symptoms, or both. Public health officials in 46 state and 2 local public health laboratories as well as the food safety laboratories of the USDA and the Food and Drug Administration submit “fingerprint” patterns of bacteria isolated from patients and/or contaminated food to the PulseNet database. The PulseNet network permits rapid comparison of the patterns in the database. Matches may indicate an outbreak. Similar patterns in samples taken from different patients suggest that the bacteria come from a common source, for example, a widely distributed contaminated food product. In addition, strains isolated from food products can be compared with those isolated from ill persons to provide evidence that a specific food caused the disease. By identifying these connections, PulseNet provides critical data for identifying and controlling the source of an outbreak, thus reducing the burden of foodborne disease for the pathogens within the scope of this network. Thirty survey respondents told us that, in the last 3 years, PulseNet had identified a cluster of cases in their state that turned out to be a previously unknown outbreak. In addition, 42 respondents reported that PulseNet helped their state detect and investigate outbreaks of E. coli O157:H7, Salmonella, Listeria, and/or Shigella. Twenty-five of these said that PulseNet greatly helped in this area. In 2000, over 17,000 patterns were submitted to the PulseNet database, and 105 potential outbreaks were identified and investigated.

Another system that CDC uses to detect potential foodborne outbreaks is the Surveillance Outbreak Detection Algorithm. In contrast to PulseNet, which uses advanced technology to compare bacterial DNA, the Surveillance Outbreak Detection Algorithm uses statistical analysis to compare currently reported incidence of two common pathogens, Salmonella and Shigella, to a historical baseline in order to detect unusual increases in a specific serotype, such as Salmonella Enteritidis. Such increases may indicate an outbreak. CDC selected Salmonella and Shigella because there are many different serotypes of these organisms, and tracking and comparing the frequency of each serotype was a task well suited for computer analysis. In addition, baseline data for these two pathogens were already available through the National Salmonella Surveillance System and the National Shigella Surveillance System, described below and in appendix III. Beginning in 2002, CDC plans to expand the system to include E. coli O157:H7. Twenty-five of the states that we surveyed told us that in their state, at least once in the last 3 years the Surveillance Outbreak Detection Algorithm had identified a cluster of cases in their state that turned out to be a previously unknown outbreak.

In addition to these 4 systems, CDC also has the following 16 systems that either collect information about a number of diseases, only some of which are foodborne, or focus solely on one disease: The Botulism Surveillance System is a national system designed to collect information about all types of botulism, including foodborne. Because every case of foodborne botulism is considered a public health emergency, CDC maintains intensive surveillance for botulism in the United States.

The CaliciNet is a network of public health laboratories that perform genetic “fingerprinting” for foodborne viruses, allowing rapid identification and comparison of strains.

The Creutzfeldt-Jakob Disease Surveillance Program monitors the occurrence of this disease through periodic review of national cause-of- death data. Surveillance for this disease was enhanced in 1996 to monitor for the possible occurrence of new variant Creutzfeldt-Jakob Disease after this new form of the disease was reported to have possibly resulted from consumption of cattle products contaminated with bovine spongiform encephalopathy (also known as “mad cow” disease).

The Epidemic Information Exchange (Epi-X) is a secure Web-based communications network that allows local, state, and federal public health officials to share and discuss outbreak data on a real-time basis. This system can immediately notify health officials of urgent public health events so that they can take appropriate actions.

The Escherichia coli O157:H7 Outbreak Surveillance System is a national system established to collect detailed information about risk factors and vehicles of transmission for E. coli infection and is used to inform the public about new vehicles of transmission.

The National Antimicrobial Resistance Monitoring System is used to monitor the antimicrobial resistance of certain bacteria that are under surveillance through other systems. The system currently operates in 17 sites throughout the United States.

The National Giardiasis Surveillance System includes data from participating states about reported cases of giardiasis—a condition caused by a parasite found in contaminated water or food such as fruits and vegetables. This system began in 1992, when the Council of State and Territorial Epidemiologists assigned giardiasis a code that enabled states to begin voluntarily reporting surveillance data on this disease to CDC electronically.

The National Notifiable Diseases Surveillance System is a national system that collects information about 58 diseases, most of which are not considered foodborne, about which regular, frequent, and timely information is considered necessary for their prevention and control. Data from the system are used to analyze disease trends and determine relative disease burdens on a national basis.

The National Salmonella Surveillance System is a national system that collects information on the isolates of Salmonella that are serotyped in state public health laboratories, as well as the isolates from food and animals. This system tracks the frequency of more than 500 specific serotypes to determine trends, detect outbreaks, and focus interventions. The system can detect outbreaks either locally or spread out over several jurisdictions.

The National Shigella Surveillance System is a national system that collects information on the isolates of Shigella that are serotyped in state public health laboratories. This system tracks the frequency of more than 40 specific serotypes to determine trends, detect outbreaks, and focus interventions. The system can detect outbreaks either locally or spread out over several jurisdictions.

The Salmonella Enteritidis Outbreak Surveillance System is a national system designed to track these outbreaks and to collect information on implicated food items and the results of traceback investigations conducted by local agencies and the Food and Drug Administration.

The Sentinel Counties Study of Viral Hepatitis is carried out in six U.S. counties to elicit more detailed information on individual hepatitis cases and collect samples for further analyses.

The Trichinellosis Surveillance System is a national surveillance system used to monitor long-term trends for this disease.

The Typhoid Fever Surveillance System is a national surveillance system for monitoring long-term trends in the epidemiology of typhoid fever in the United States. The system provides information about risk factors that is used in making vaccine recommendations.

The Vibrio Surveillance System is composed of two parts: a national system used for reporting cases of Vibrio cholerae (cholera), and another system, which is more geographically limited, that is used for reporting all Vibrio infections. All cases reported to this system are confirmed through laboratory tests by the relevant state or CDC. Surveillance data for this system are used to identify environmental risk factors, retail food outlets where high-risk exposures occur, and target groups that may benefit from consumer education.

The Viral Hepatitis Surveillance Program is a national system designed to collect information about acute cases of viral hepatitis: hepatitis A; hepatitis B; and non-A, non-B hepatitis (including hepatitis C). States report basic demographic information for each case, as well as other factors, such as risk-factor information. These data are essential for monitoring trends in the characteristics of the various types of viral hepatitis.

Collectively, these surveillance systems provide crucial national data needed to detect and control the spread of foodborne disease. More detailed information about these systems is contained in appendix III, in alphabetical order by system.

Delayed Reporting and Incomplete Data Limit CDC’s Surveillance Systems, but CDC Is Working to Address These Problems

Public health officials that we contacted said that both untimely release of surveillance data by CDC and the gaps in some of CDC’s data limit the surveillance systems’ usefulness. Some of these problems have resulted from staff shortages at CDC, while others have been caused by shortages of trained epidemiologists and laboratory personnel at state and local health departments. Another contributing factor is that each state decides which diseases it will track and which ones it will not. Therefore, the diseases that are reported to CDC vary from one state to another. In response to these problems, CDC has taken action to address its staff deficiencies and to assist state and local health officials to improve their data collection and reporting abilities. CDC’s actions represent a good first step toward providing public health officials with more timely and complete surveillance data.

Delayed Reporting

Delayed dissemination of information from CDC’s foodborne disease surveillance systems has impaired the usefulness of the data. For example, for the Foodborne Disease Outbreak Surveillance System, CDC did not publish outbreak data for the years 1993–1997 until March 2000. CDC officials told us that the late publication of the March 2000 outbreak report was due in part to staff shortages. As of June 2001, data from 1997 was the most recent available from this system. Officials from both the Food and Drug Administration and USDA’s Food Safety and Inspection Service told us that this delay limited the data’s usefulness. In addition, of the 52 respondents to our survey, 26 said that the 3-year lag between the end of the reporting period and the publication of CDC’s March 2000 report diminished the usefulness of the report to their state. Of the 43 survey respondents that used this report, nearly all said that the outbreak data was used as a source of information about foodborne disease trends or to determine associations between pathogens and food.

Many survey respondents also told us that more rapid reporting or release of data from FoodNet, PulseNet, and the Surveillance Outbreak Detection Algorithm would improve the systems’ usefulness. For FoodNet, CDC publishes surveillance results annually. However, as of June 2001, CDC had not published any detailed results from its case control studies about the proportion of foodborne disease caused by specific foods or food preparation and handling practices, even though FoodNet has been operational since 1995. CDC officials told us that they had submitted the results of these surveys and studies to professional journals, but the results were never published. For PulseNet, nearly half of the survey respondents said that more rapid analysis of data and more rapid reporting of identified clusters would make the system more useful. In addition, 33 of the respondents said that direct access to the PulseNet database would make the system more useful. For the Surveillance Outbreak Detection Algorithm, 25 of the respondents said that more rapid analysis of state, regional, and national data by CDC would make that system more useful. In addition, 20 respondents said more rapid reporting of clusters by CDC would make the system more useful.

CDC officials told us that the late publication of the March 2000 outbreak report was due in part to staff shortages. CDC took action to address this problem when the agency hired four new staff between June 2000 and September 2000 to take on the responsibilities of collecting, verifying, coding, processing, and summarizing the outbreak data in addition to other duties. In the future, CDC plans to release outbreak data annually beginning with 1998 data, instead of aggregating these data over several years. CDC is currently compiling 2001 outbreak data and intends to publish it by the end of 2002. In addition, CDC is developing a system, called the Electronic Foodborne Outbreak Reporting System, which will allow states to electronically transmit reports of foodborne disease outbreaks. Thirty-six survey respondents indicated that this system would increase the timeliness of their initial outbreak reports to CDC. Finally, in November 2000 CDC introduced an electronic bulletin board, known as Epi-X, which allows local, state, and federal public health officials to share outbreak data on a real-time basis. This system can automatically notify health officials of urgent public health events so that they can take appropriate actions.

CDC also has plans to provide more rapid reporting or release of data from FoodNet and PulseNet. For FoodNet, CDC officials said they plan to publish by the end of 2001 a number of case control study results that were previously unavailable. For PulseNet, CDC told us it has developed new software that, effective June 30, 2001, gives all participating certified laboratories direct access to the PulseNet database. This allows state officials to query the PulseNet database directly instead of waiting for CDC to send them notice of a new pattern.

However, CDC’s ability to disseminate surveillance data in a timely fashion also depends in part on the timeliness of state and local officials’ submittal of the data. For example, for the Foodborne Disease Outbreak Surveillance System, 24 of the survey respondents said they did not report any outbreak data for 2000 until the end of the year or even later. Thus, data could be over a year old before it gets reported to CDC. Similarly, CDC officials also told us that for the Surveillance Outbreak Detection Algorithm, some states report information only quarterly, which is too late to allow CDC to provide early detection of an ongoing outbreak. Because responsibility for surveillance of foodborne diseases rests primarily with the states, states’ reporting of data to CDC is voluntary. To assist in overcoming this problem, CDC is developing a new program known as the National Electronic Disease Surveillance System. This system is intended to facilitate the ready exchange of data between local and state health departments, among states, and among states and CDC. While this may not overcome delayed reporting by the states, it should make information more readily available. In addition, through their Epidemic Intelligence Service program, CDC is training medical doctors, researchers, and scientists, who serve in 2-year assignments, about the needs of both state health departments and CDC. Agency officials said that they hope graduates from the program will understand the value of sharing information in a timely manner and help speed the flow of information into CDC.

Incomplete Data

The completeness of CDC’s data is dependent in large part on the submissions from state and local health officials, which often do not report all cases or all information requested about individual cases. For example, 17 survey respondents told us that not all of the outbreaks in their states were reported to the Foodborne Disease Outbreak Surveillance System. Moreover, for those outbreaks that were reported, 25 survey respondents said the responsible pathogen was identified in only half or fewer of their reports submitted to CDC. Further, as regards the contaminated food item that caused the outbreaks, 28 survey respondents said they identified and reported the responsible food item in half or fewer of their reports. According to FDA and FSIS officials, identifying the responsible pathogen and the contaminated food item is critical for understanding and controlling foodborne disease, and for tracing the cause of the contaminant to its original source.

Survey respondents cited several reasons for the gaps in outbreak information sent to CDC. Table 1 summarizes some of the major reasons.

As the table shows, the majority of the respondents said shortages of personnel and capacity in state and local health departments, among other things, hinder their ability to detect and investigate foodborne disease outbreaks. A complete listing of conditions that could hinder state and local public health officials is included in our questionnaire results, contained in appendix I.

Another cause of incomplete data submissions to the Foodborne Disease Outbreak Surveillance System, as well as to other systems, is the lack of standard disease reporting requirements among states. Each state has a separate list of “reportable” diseases that must be reported to the state health department. The lists vary greatly from state to state because of differences in the extent to which the diseases occur. For example, while 32 survey respondents indicated that health providers in their state are required to notify state or local health departments about cases of cyclosporiasis, 19 said notification was not required. (See app. I for more information on state reporting requirements for a number of foodborne pathogens.) Although states can forward data to CDC about diseases that are not reportable, overall data about such diseases are often incomplete because of deficiencies in reporting by physicians and labs.

To improve local and state health officials’ ability to respond to a broad range of public health issues relating to infectious diseases, which include foodborne outbreaks, CDC provides funding to state and local health departments through its Emerging Infections Programs and its Epidemiology and Laboratory Capacity program. Funding for these two programs has increased from $900,000 in 1994 to approximately $50 million in 2001. These programs are designed to address staffing or technology shortages, or both, and will help the states provide CDC with more complete information. For example, states have received grants to significantly increase the capacity of their laboratories. According to CDC officials, now nearly every state has properly trained staff able to use PulseNet technology.

To encourage more standardized reporting among the states, CDC consults annually with the Council of State and Territorial Epidemiologists to determine which infectious diseases, including foodborne diseases, are important enough to merit routine reporting to CDC. Officials from CDC told us they have also entered into cooperative agreements with the council and with the Association of Public Health Laboratories to assess the states’ capability and capacity to address public health issues, including foodborne diseases.

Agency Comments

In commenting on a draft of this report, CDC officials generally agreed with the overall message of the report and provided technical comments to ensure completeness and accuracy. We incorporated these comments into our report as appropriate. CDC comments are presented in appendix IV.

Scope and Methodology

To describe CDC’s foodborne disease surveillance systems, we obtained information from CDC on the systems used most often in conducting foodborne disease surveillance activities. We examined each of these systems to identify their use and how they operate. We also discussed the systems’ use and operation with officials from the Food and Drug Administration, USDA’s Food Safety and Inspection Service, the Council of State and Territorial Epidemiologists, the Association of Public Health Laboratories, the National Pork Producers Council, the American Meat Institute, the National Broilers Council, and the Center for Science in the Public Interest. As a result of our initial work, we then directed the remainder of our review effort to four surveillance systems that focus on foodborne disease and that cover more than one pathogen. These four systems were the Foodborne Disease Outbreak Surveillance System, FoodNet, PulseNet, and the Surveillance Outbreak Detection Algorithm. We reviewed extensive literature about each of these four systems and examined the systems’ input and reporting documentation.

To identify limitations of these surveillance systems, we sent mail-back questionnaires to officials in the 50 state health departments, as well as in the District of Columbia, and New York City. We pretested this survey in three states to ensure that our questions were clear, unbiased, and precise, and that responding to the survey did not place an undue burden on the health departments. We received completed questionnaires from 100 percent of those surveyed. We discussed limitations identified in the survey with CDC and other federal and state public health officials and with other groups that use foodborne disease surveillance systems. To identify initiatives designed to address these limitations, we met with CDC officials responsible for the surveillance systems and discussed actions they have taken or plan to take to address the limitations.

We conducted our review from August 2000 through July 2001 in accordance with generally accepted government auditing standards.

As agreed with your offices, unless you publicly announce the contents of this report earlier, we plan no further distribution of it until 30 days from the date of this letter. We will then send copies to the congressional committees with jurisdiction over food safety issues; the Secretary of Health and Human Services; the Director, Office of Management and Budget; and other interested parties. We will also provide copies to others on request.

If you or your staff have any questions about this report, please call me on (202) 512-3841. Key contributors to this report are listed in appendix V.

Appendix I: Questionnaire Results

Appendix II: Major Foodborne Pathogens Under Surveillance by the Centers for Disease Control and Prevention

Appendix II: Major Foodborne Pathogens Under Surveillance by the Centers for Disease Control and Prevention Fever, abdominal cramps, diarrhea (often bloody)

Profuse watery diarrhea, vomiting, circulatory collapse, shock Fever, abdominal pain, diarrhea (often bloody)

Person-to-person or by contaminated food or water (fecal-oral)

Contaminated food or water; person to person; contact with a contaminated item (fecal-oral)

Appendix III: CDC’s Surveillance Systems for Foodborne Disease

Botulism Surveillance System

The Botulism Surveillance System was established in 1973 to collect detailed information about all types of botulism—foodborne, wound, infant, and child or adult. Because every case of foodborne botulism is considered a public health emergency, CDC maintains intensive surveillance for botulism in the United States. All states except California and Alaska must contact CDC when a case of botulism is suspected, because CDC is the main source of the antitoxin used to treat botulism. As a result, most cases of botulism are reported to CDC immediately. CDC officials follow up on these cases to collect demographic information about the affected individuals, as well as additional information about which foods were involved and their handling and preparation. This information is especially important because the hazardous food may still be available.

Geographic Scope: National.

Pathogen: Clostridium botulinum.

Cases Reported: In 1999, a total of 174 cases were reported to this system, of which 26 were foodborne.

CaliciNet, an initiative currently under development, is a network of public health laboratories that uses DNA sequence analysis for “fingerprinting” of foodborne viruses. The network permits rapid comparison of the genetic patterns of foodborne caliciviruses through an electronic sequence database at CDC. Laboratories participating in CaliciNet detect “Norwalk- like” viruses in samples from patients involved in outbreaks of gastroenteritis. Depending on the capabilities in the laboratory, amplification products from positive samples are sequenced locally, sent to a contract laboratory for sequencing, or sent to CDC for confirmatory testing and sequencing. Comparison of newly identified sequences with those in the database may help public health laboratories to identify cases with a common source.

Geographic Scope: Thirteen state health departments (California, Florida, Idaho, Iowa, Maryland, Michigan, Minnesota, Missouri, New York, Oregon, Virginia, Washington, and Wisconsin) and the Los Angeles County health department are currently submitting samples for confirmatory testing and genetic analysis. Ten other state health departments (Colorado, Connecticut, Illinois, Nevada, New Hampshire, New Mexico, Ohio, Rhode Island, South Carolina, and Tennessee) are currently undergoing proficiency testing.

Pathogens: “Norwalk-like” viruses and “Sapporo-like” viruses.

Cases Reported: In 1999, 94 specimens from 9 states were submitted for confirmatory testing and genetic analysis at CDC.

Creutzfeldt-Jakob Disease Surveillance Program

CDC monitors the occurrence of Creutzfeldt-Jakob disease through periodic review of national multiple-cause-of-death data. Surveillance for this disease was enhanced in 1996 to monitor for the possible occurrence of new variant Creutzfeldt-Jakob disease after this new form of the disease was reported to have possibly resulted from consumption of cattle products contaminated with bovine spongiform encephalopathy (also known as “mad cow” disease).

One enhancement focused on striking differences in the age distribution of new variant Creutzfeldt-Jakob disease cases, for which the median age at death is 28 years, from that of sporadic cases of Creutzfeldt-Jakob disease in the United States, for which the median age at death is 68 years. This enhancement included an ongoing review of the clinical and pathologic records of U.S. victims of Creutzfeldt-Jakob disease under 55 years of age.

In addition, in collaboration with the American Association of Neuropathologists, CDC established a National Prion Disease Pathology Surveillance Center to facilitate neuropathologic evaluation of patients suspected of having Creutzfeldt-Jakob disease or other diseases caused by prions.

Geographic Scope: National.

Pathogens: The agents of Creutzfeldt-Jakob disease and the new variant form of Creutzfeldt-Jakob are believed to be prions.

Cases Reported: Between January 1979 and June 2001, over 5,000 U.S. cases of Creutzfeldt-Jakob disease were reported; no evidence of the occurrence of new variant Creutzfeldt-Jakob disease in the United States was detected.

Epidemic Information Exchange (Epi-X)

The Epidemic Information Exchange, known as Epi-X, is a secure, Web- based communications network for public health officials that simplifies and expedites the exchange of routine and emergency public health information among state and local health departments, CDC, and the U.S. military. CDC recognized that the public health profession had a need for rapid communication, research, and response to widespread food and food-product contamination. After consulting with more than 300 health officials, CDC developed this new system, which enables federal, state, and local epidemiologists, laboratory staff, and other health professionals to quickly notify colleagues of disease outbreaks as they are identified and investigated. The system allows users to compare information on current and past outbreaks through an easily searchable database, discuss a response to the outbreak with colleagues through e-mail, Internet, and telecommunications capabilities, and request epidemiological assistance from CDC on-line. Epi-X is endorsed by the Council of State and Territorial Epidemiologists.

Geographic Scope: National.

Pathogens: Any pathogen, including bacteria, chemicals, parasites, and viruses (also products or devices).

Cases Reported: From November 2000 through August 2001, 153 outbreaks were reported, including 37 foodborne outbreaks. Two health alerts related to foodborne outbreaks of food contamination were issued; over 85 percent of Epi-X users were notified within 30 minutes.

Escherichia Coli O157:H7 Outbreak Surveillance System

The Escherichia coli (E. coli) O157:H7 Outbreak Surveillance System began in 1982, after the first recognized outbreak of this pathogen, and was established to collect detailed information about risk factors and vehicles of transmission for E. coli infection. State health departments are encouraged to report any outbreak of E. coli O157:H7 infection in their state to CDC. Data are collected on outbreaks caused by all sources including food, recreational water, drinking water, animal contact, and person-to-person transmission. E. coli O157:H7 infections can be quite serious and may result in death. Therefore, public health officials at CDC follow up with state health departments on reported outbreaks of E. coli infection to determine their cause and prevent additional spread. Data from this surveillance system are used to inform the public about new vehicles of transmission.

Geographic Scope: National.

Pathogen: E. coli O157:H7.

Cases Reported: In 1999, 38 confirmed outbreaks (causing 1,897 illnesses) were reported to CDC.

Foodborne Disease Outbreak Surveillance System

CDC created the Foodborne Disease Outbreak Surveillance System in 1973 to collect data about cases of foodborne disease that are contracted by two or more patients as a result of ingesting a common food. In the event of such an outbreak, state and local public health department officials provide data to the system about the pathogen that caused the outbreak, the contaminated food that was involved, and contributing factors associated with foodborne disease outbreaks. The data help focus public health actions intended to reduce illnesses and deaths caused by foodborne disease outbreaks. Trend analysis of the data shows whether outbreaks occur seasonally and whether certain foods are more likely to contain pathogens. It also helps public health officials identify critical control points in the path from farm to table that can be monitored to reduce food contamination. However, the data from this system do not always identify the pathogen responsible for a given outbreak; such identification may be hampered by delayed or incomplete laboratory investigation, inadequate laboratory capacity, or inability to recognize a particular pathogen as a cause of foodborne disease.

Geographic Scope: All 50 states, the District of Columbia, Guam, Puerto Rico, and the U.S. Virgin Islands.

Pathogens: Any pathogen, including bacteria, chemicals, parasites, and viruses.

Cases Reported: In 1997, 806 outbreaks were reported to CDC through this system.

The Foodborne Diseases Active Surveillance Network, also known as FoodNet, is a collaborative project of the CDC, the USDA, the Food and Drug Administration, and nine sites that gathers information about nine foodborne pathogens, two syndromes, and toxoplasmosis. A significant distinction between FoodNet and other foodborne surveillance systems is that FoodNet participants actively and routinely contact the clinical laboratories in their areas to collect information about the number of cases of each disease covered by this system. For other systems, state and local reporting practices to CDC may not be consistent from state to state.

In addition to the active surveillance efforts, FoodNet participants conduct studies and surveys of the physicians, laboratories, and populations within the nine sites. Case control studies are used to determine risk factors, such as food preparation or handling practices, for acquiring infections from the pathogens covered by the system, as well as the association between these infections and specific foods. These studies have been conducted for E. coli O157:H7, Salmonella, Campylobacter, and others. CDC also collects information through population surveys, in which individuals who live in a FoodNet catchment area and were not part of a case control study are surveyed about their consumption of certain foods and how often they see a physician. To determine which tests are typically performed at laboratories in FoodNet areas, CDC administers laboratory surveys. Finally, state officials in the FoodNet areas have administered two physician surveys. The first survey asked physicians to describe actions they take when seeing a patient with a possible foodborne illness, while the second asked how they educate patients about foodborne diseases. FoodNet data can also test the efficacy of interventions designed to reduce the incidence of foodborne pathogens.

Geographic Scope: Nine sites consisting of parts or all of the states of California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New York, Oregon, and Tennessee.

Pathogens: Nine pathogens—Campylobacter, Cryptosporidium, Cyclospora, E. coli O157:H7, Listeria monocytogenes, Salmonella, Shigella, Vibrio, Yersinia enterocolitica—and hemolytic uremic syndrome (a serious complication of E. coli O157:H7 infection), Guillain- Barre syndrome (a serious complication of Campylobacter infection), and toxoplasmosis.

Cases Reported: The number of cases varies by pathogen.

National Antimicrobial Resistance Monitoring System—Enteric Bacteria

The National Antimicrobial Resistance Monitoring System for Enteric Bacteria began in 1996 as a collaborative effort among CDC, the Food and Drug Administration, and USDA. Its purpose is to monitor the resistance of human enteric (intestinal) bacteria. Participating health departments forward some portion of their isolates for six types of bacteria to CDC for susceptibility testing. Susceptibility testing involves determining the sensitivity of the bacteria toward 17 antimicrobial agents that inhibit their growth. Campylobacter isolates are submitted only by the FoodNet sites and are tested against 8 antimicrobial agents instead of 17. Because these data have been collected continually since 1996, trend analyses are possible. This can provide useful information about patterns of emerging resistance, which in turn can guide mitigation efforts.

Geographic Scope: Seventeen state and local public health laboratories in California, Colorado, Connecticut, Florida, Georgia, Kansas, Los Angeles County, Maryland, Minnesota, Massachusetts, New Jersey, New York City, New York, Oregon, Tennessee, Washington, and West Virginia participate in this system.

Pathogens: Campylobacter, Enterococcus, E. coli O157:H7, Salmonella non-typhoidal, Salmonella typhi, and Shigella.

Cases Reported: The number of cases varies by pathogen.

National Giardiasis Surveillance System

The National Giardiasis Surveillance System began in 1992 when the Council of State and Territorial Epidemiologists assigned giardiasis a code that enabled states to voluntarily report giardiasis cases to CDC electronically. For each case, basic information is collected, such as the age, sex, and race of the patient, as well as the place and time of infection. This surveillance system provides data used to educate public health practitioners and health-care providers about the scope and magnitude of giardiasis in the United States. The data can also be used to establish research priorities and to plan future prevention efforts. In June 2001, the Council of State and Territorial Epidemiologists voted to add giardiasis to the list of Nationally Notifiable Diseases.

Geographic Scope: Forty-three states, the District of Columbia, New York City, Guam, and Puerto Rico.

Pathogen: Giardia intestinalis (also known as Giardia lamblia).

Cases Reported: In 1999, over 23,000 cases of giardiasis were reported to CDC through this system.

National Notifiable Diseases Surveillance System

The National Notifiable Diseases Surveillance System collects information about 58 diseases designated as nationally notifiable—that is, diseases about which regular, frequent, and timely information regarding individual cases is considered necessary for their prevention and control. The first annual report on notifiable diseases was published in 1912 for 10 diseases. CDC assumed responsibility for the collection and publication of this data in 1961. The list of nationally notifiable diseases is revised periodically to include emerging pathogens and to delete those whose incidence has declined significantly. CDC also publishes provisional figures for some of these diseases weekly.

Policies for reporting notifiable disease cases can vary by disease or reporting jurisdiction, depending on case status classification (i.e., confirmed, probable, or suspect). Reporting of diseases is mandated by legislation or regulation only at the state and local level. Thus, the list of diseases considered notifiable varies slightly by state. Public health officials report basic information for each case, such as age, sex, and race of the patient, as well as the place and time of infection. The data reported in the annual summaries for this system are useful for analyzing disease trends and determining relative disease burdens.

Geographic Scope: National.

Pathogens/Diseases: Botulism, cholera, cryptosporidiosis, cyclosporiasis, E. coli, hepatitis A, listeriosis, salmonellosis, shigellosis, trichinosis, and typhoid fever (also 47 other pathogens or diseases, which are not considered to be foodborne).

Number of Cases Reported: The number of cases varies by disease.

National Salmonella Surveillance System

The National Salmonella Surveillance System began in 1962 when the Council of State and Territorial Epidemiologists and the Association of Public Health Laboratories agreed that state public health laboratories would routinely test samples of Salmonella to determine their serotype and report the results to CDC. For many years these reports were submitted as paper forms, but for the last 10 years, reporting has been electronic. In addition to the specific serotype, the reports include the age, sex, and county of residence of the person from whom the sample was isolated, the clinical source (such as stool, blood, or abscess), and the date the sample was received in the state laboratory. CDC maintains the national reference laboratory for Salmonella and provides the laboratory reagents and training needed to determine the serotypes. These data are used to identify long-term trends and specific populations at risk for infection, detect and investigate outbreaks, and monitor the effectiveness of prevention efforts.

Geographic Scope: All 50 states, New York City, and Guam.

Pathogens: Salmonella enterica.

Cases Reported: In 1999, approximately 32,750 cases were reported to CDC through this system.

National Shigella Surveillance System

The National Shigella Surveillance System began in 1963 when the Council of State and Territorial Epidemiologists and the Association of Public Health Laboratories agreed that state public health laboratories would routinely test samples of Shigella to determine their serotype and report the results to CDC. For many years these reports were submitted as paper forms, but for the last 10 years, reporting has been electronic. In addition to the specific serotype, the reports include the age, sex, and county of residence of the person from whom the sample was isolated, the clinical source (such as stool, blood, or abscess), and the date the sample was received in the state laboratory. CDC maintains the national reference laboratory for Shigella and provides the laboratory reagents and training needed to determine the serotypes. These data are used to identify long- term trends and specific populations at risk for infection, detect and investigate outbreaks, and monitor the effectiveness of prevention efforts.

Geographic Scope: All 50 states, New York City, and Guam.

Pathogen: Shigella species.

Cases Reported: In 1999, approximately 12,000 cases were reported to CDC through this system.

PulseNet is a national network of public health laboratories that, since 1996, has been using standardized methods to perform genetic “fingerprinting” of four types of foodborne bacteria. The network permits rapid comparison of the bacteria’s genetic patterns through an electronic database at CDC. Laboratories participating in PulseNet use a method called pulsed-field gel electrophoresis to identify the genetic patterns in bacterial pathogens isolated from patients and from suspected food items. Once the patterns are generated, they are entered into an electronic database of patterns at the state or local health department and transmitted to CDC where they are filed in the PulseNet database. If patterns submitted by laboratories during a defined time period are found to match, CDC will alert the laboratory officials of the match so that a timely investigation can be performed.

PulseNet can help public health authorities recognize when cases of foodborne illness occurring at the same time in geographically separate locales are caused by the same strain of bacteria and may be due to a common exposure, such as a food item. An epidemiologic investigation of those cases can then determine what they have in common. If a bacterial pathogen is isolated from a suspected food, the pathogen’s genetic pattern can be quickly compared with the patterns of pathogens isolated from patients. Matching patterns can indicate possible nationwide outbreaks and lead to public health actions such as epidemiologic investigations, product recalls, and long-term prevention measures.

Geographic Scope: 46 state and 2 local public health laboratories—New York City and Los Angeles County—and the food safety laboratories of the Food and Drug Administration and USDA.

Pathogens: E. coli O157:H7, Salmonella, Listeria, and Shigella.

Cases Reported: In 2000, over 17,000 patterns were submitted to the CDC PulseNet database, and 105 potential outbreaks were investigated by state and local officials.

Salmonella Enteritidis Outbreak Surveillance System

The Salmonella Enteritidis Outbreak Surveillance System began in 1985. This passive system collects reports of outbreaks as they occur throughout the calendar year. States are encouraged to report any outbreak of Salmonella Enteritidis infection in their state to CDC. The surveillance system tracks morbidity and mortality associated with outbreaks and collects information on implicated food items and on the results of traceback investigations conducted by local agencies and the Food and Drug Administration. Surveillance data have been used to identify risk factors for Salmonella Enteritidis infection, contaminated food items, and groups that may benefit from education.

Geographic Scope: National.

Pathogen: Salmonella Enteritidis.

Outbreaks Reported: In 1999, 44 confirmed outbreaks of Salmonella Enteritidis were reported, affecting U.S. residents in 17 states.

Sentinel Counties Study of Viral Hepatitis

The Sentinel Counties Study of Viral Hepatitis began in 1979 to collect more detailed information on risk factors for cases of acute viral hepatitis and to detect newly emerging viruses. Under contracts with CDC, county health departments collect data for each reported case and a serum sample for each reported case and report the information to CDC. In recent years, data from this system have been used to better characterize hepatitis A epidemiology and to develop molecular subtyping techniques.

Geographic Scope: Six counties–Pinellas, Florida; Jefferson, Alabama; Denver, Colorado; Pierce, Washington; Multnomah, Oregon; and San Francisco, California.

Pathogens: Hepatitis A; hepatitis B; and non-A, non-B hepatitis (including hepatitis C).

Cases Reported: In 1999, 240 cases of hepatitis A, 134 cases of hepatitis B, and 32 cases of non-A, non-B hepatitis (including hepatitis C) were reported to CDC through this system.

Surveillance Outbreak Detection Algorithm

The Surveillance Outbreak Detection Algorithm was designed to detect unusual clusters of cases of a foodborne disease that indicate a potential outbreak. The algorithm was first used in 1996 for Salmonella cases. The algorithm compares, by serotype, the number of cases reported through the Public Health Laboratory Information System during a given week with a 5-year historical baseline for that serotype and week to detect unusual increases from the baseline. The weekly comparisons are done on a national, regional, and state basis. If they detect any unusual clusters, CDC notifies the affected state(s) by fax.

The Surveillance Outbreak Detection Algorithm is useful for identifying multistate outbreaks, especially where individual cases may be quite diffuse. The software also has an interface with which any user can easily generate basic statistical information. The interface also produces graphs and maps to facilitate identification of trends or anomalies. State health departments have access to a limited version of the algorithm via the Public Health Laboratory Information System.

Geographic Scope: National.

Pathogens: Salmonella and Shigella.

Cases Reported: Using the algorithm, CDC officials identified 133 potential Salmonella outbreaks in 1999 and 273 in 2000.

Trichinellosis Surveillance System

The Trichinellosis (Trichinosis) Surveillance System was created in 1947, when the U.S. Public Health Service began collecting statistics on cases of infection at the national level. In 1965, trichinellosis was included among the notifiable diseases that physicians report weekly to state health departments and to CDC through the National Morbidity Reporting System. A standardized surveillance form was developed to collect detailed information for each case.

Geographic Scope: National.

Pathogen: Trichinella spp.

Cases Reported: In 1999, 12 cases were reported to CDC through this system.

Typhoid Fever Surveillance System

The Typhoid Fever Surveillance System was established in 1962 to collect detailed information about all cases of Salmonella typhi. State health department officials are asked to complete a typhoid fever surveillance report form when a laboratory confirms a case of typhoid fever. The form collects demographic information about each case, as well as information about patients’ international travel and vaccination history, and the antibiotic susceptibility of isolates. This information is especially important for developing travel advisories, vaccination recommendations, and treatment guidelines.

Geographic Scope: National.

Pathogen: Salmonella typhi.

Cases Reported: In 1999, 115 cases were reported to this system.

Vibrio Surveillance System

The Vibrio Surveillance System began in 1988 and is composed of two parts. One is a national passive system for reporting cases of toxigenic Vibrio cholerae infection (cholera), and the other is a more active system that covers all types of Vibrio infections in a more limited geographic area. For the active system, investigators use a standardized form to collect clinical data, information about patients’ underlying illnesses, and epidemiologic data about patients’ seafood consumption and exposure to seawater for the week preceding illness. Surveillance data have been used to identify environmental risk factors, retail food outlets where high-risk exposures occur, and groups that may benefit from consumer education.

Geographic Scope: National for the cholera portion of the system; the non-cholera portion of the system initially included only the Gulf Coast states of Alabama, Florida, Louisiana, and Texas but is open to all states and has expanded to include, among others, the FoodNet sites and states along both the East and West coasts.

Pathogen: Toxigenic Vibrio cholerae; Vibrio spp.

Cases Reported: In 2000, four cases of Vibrio cholerae and 295 laboratory-confirmed cases of other types of Vibrio infections were reported to CDC through this system.

To enhance the accuracy and completeness of reporting, CDC requests that participating states verify the information reported twice a year.

Viral Hepatitis Surveillance Program

The Viral Hepatitis Surveillance Program was created in 1961 to collect demographic, clinical, serologic, and risk-factor information on cases of acute viral hepatitis. The data collected through the program are essential for monitoring trends in the epidemiologic characteristics of the various types of viral hepatitis. These data are also valuable for monitoring the effectiveness of prevention programs.

Pathogens: Hepatitis A; hepatitis B; non-A, non-B hepatitis (including hepatitis C).

Geographic Scope: National.

Number of Cases Reported: In 1999, 17,047 cases of hepatitis A, 7,694 cases of hepatitis B, and 3,111 cases of non-A, non-B hepatitis were reported through National Electronic Telecommunication Surveillance System. Information about risk factors was reported through the Viral Hepatitis Surveillance Program for approximately 33 percent of these cases.

Source of Data: States report this information to CDC through the extended-record capability of the National Electronic Telecommunication Surveillance System or by submitting a paper form with this information.

Appendix IV: Comments From the Centers for Disease Control

Appendix V: GAO Contacts and Staff Acknowledgments

GAO Contacts

Staff Acknowledgments

In addition to those named above, Carolyn Boyce, Cathy Helm, Natalie Herzog, Cynthia Norris, Paul Pansini, and Stuart Ryba made key contributions to this report.