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 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.