Food Safety and Inspection Service United States Department of Agriculture Washington, D.C. 20250-3700

Backgrounders

February 1998

Foodborne Diseases Active Surveillance Network (FoodNet)

The U.S. Department of Agriculture's Food Safety and Inspection Service (FSIS), the Food and Drug Administration (FDA), and the Centers for Disease Control and Prevention (CDC) are collaborating with state health departments and local investigators at seven locations across the country to identify more accurately the incidence of foodborne illness in the United States. Through the Foodborne Diseases Active Surveillance Network (FoodNet), the agencies involved will be better able to track the incidence of foodborne illness and monitor the effectiveness of food safety programs in reducing foodborne illness.

Background

FSIS ensures the safety, wholesomeness, and accurate labeling of meat, poultry, and egg products. FDA ensures the safety and wholesomeness of foods other than meat and poultry. CDC monitors the rates of foodborne diseases in the United States, investigates outbreaks of foodborne illnesses, and facilitates efforts to prevent foodborne disease.

Traditionally, foodborne diseases are reported to local and state health departments and to CDC through passive surveillance systems or laboratory-based reporting systems. Current data from these systems are used to estimate that there are 6 million to 33 million cases of bacterial foodborne diseases in the United States each year. However, these systems do not provide precise estimates to evaluate food safety reforms and program changes, nor how they will affect the incidence of foodborne disease.

These existing "passive" systems rely on a number of events. First, an individual with foodborne illness must choose to seek medical care. Then, the patient's physician must decide to collect cultures and request laboratory analysis. And finally, results must be reported to state health departments and then to the CDC. If any step in the process is missed, the case goes unreported. CDC estimates that only one to five percent of foodborne disease cases are reported.

To overcome the difficulties caused by such a large number of unreported cases, the collaborating FoodNet sites have set up a system to actively identify laboratory-confirmed cases of foodborne illness and to perform surveys to more accurately estimate the actual number of people who become sick with diarrhea each year.

FoodNet is in keeping with the National Academy of Sciences' recommendation for more community-based surveillance of pathogens and of foodborne disease incidence in humans. The project measures the impact of programs aimed at reducing the pathogens on meat and poultry.

The program, originally known as the Sentinel Site Survey, began with a 3-month trial in 1995, and has been actively collecting data since January 1996. Coordinated by CDC, data is collected at sites in Atlanta, GA, at Emory University and the Veteran's Affairs Medical Center; in northern California at the California Department of Health Services and the University of California at Berkeley; in Connecticut at the Connecticut Department of Public Health and Addiction Services, and Yale University; in Minnesota at the Minnesota Department of Health; and in Oregon at the Oregon State Health Division. And, beginning in January 1997, an additional county in Connecticut and 12 counties in Georgia were added to FoodNet. This increased the population under surveillance by an additional 1.5 million to now include 14.7 million people. Also, investigators in New York and Maryland joined the program and now conduct active surveillance in several counties within their states.

Data is collected through: population-based surveys; laboratory surveys; physician surveys; and case-control studies.

Laboratory Survey

Laboratories that conduct microbiological testing of stool samples were surveyed to determine their practices for processing and culturing samples. They are reporting results from cultures so that FoodNet can determine the number of culture-confirmed cases of foodborne bacterial illnesses.

Population Survey

The population-based surveys are intended to develop estimates of the numbers of diarrheal cases that occur in the study population each year, the proportion of persons with diarrhea who seek health care, and their food handling behaviors and practices. Data is being gathered through random telephone surveys with individuals who reside within the sites.

Physician Survey

The primary purpose of the initial physician survey is to determine how often and under what circumstances physicians order tests. As changes occur in the way health care is provided over time, FoodNet will monitor how those changes affect stool culturing practices.

Case-control Studies

Case-control studies are used to statistically determine risks associated with different foods and to obtain information on potential exposure. Case-control studies consist of interviews with selected persons who had laboratory-confirmed cases of Salmonella or E. coli O157:H7, and a random selected control group of people in the community who were not ill.

The FoodNet program specifically targets seven bacterial pathogens--Campylobacter, E. coli O157:H7, Listeria, Salmonella, Shigella, Vibrio, and Yersinia. In addition, the case-control studies seek to develop a better understanding of two of those pathogens, Salmonella and E. coli O157:H7.

In 1997, FoodNet began active surveillance for hemolytic uremic syndrome (HUS), a serious potential outcome of infections caused by E. coli O157:H7 and other Shiga toxin producing E. coli infections. In addition, FoodNet initiated active surveillance for Cryptosporidia and Cyclospora at three of the survey sites.

First Year's Results

FoodNet completed its first year of gathering data on December 31, 1996. Results from the first year of the study were published by CDC in the March 28, 1997, issue of the Morbidity and Mortality Monthly Report (MMWR) (copies of the MMWR are available through the Internet at http://www.cdc.gov/epo/mmwr/mmwr.html).

FoodNet found 7,259 laboratory-confirmed diarrheal cases attributable to the 7 bacterial pathogens targeted. Of those cases, 45 percent--or 3,267 cases--were attributed to Campylobacter. Salmonella was identified in 29.5 percent (2,142 cases), Shigella in 17.2 percent (1,251 cases), E. coli O157:H7 in 5.3 percent (384 cases), Yersinia in 1.9 percent (135 cases), Listeria in 0.9 percent (63 cases), and Vibrio in 0.2 percent (17 cases).

An important benefit of the data collection is the identification of outbreaks which might previously have gone undetected or treated as isolated cases.

How Data Will Be Used

FSIS, FDA, CDC, and the project sites will use FoodNet information to monitor the incidence of foodborne diseases in the United States. Outbreaks identified during this surveillance project will be investigated and appropriate control measures taken. This system will help identify new and emerging foodborne pathogens.

FSIS will use the pathogen data to evaluate the effectiveness of new food safety programs and regulations in reducing foodborne pathogens on meat and poultry. In July 1996, the Agency published a final rule requiring meat and poultry plants to begin implementing pathogen reduction and hazard analysis and critical control point (HACCP) systems to reduce microbial contamination. The rule mandates microbial testing for Salmonella to verify the effectiveness of HACCP procedures in reducing pathogenic organisms in meat and poultry.

FDA published a final rule implementing HACCP principles for seafood in December 1995. The provisions of that rule took effect on December 18, 1997. FDA will include data from FoodNet in its evaluation of the effectiveness of HACCP systems as well as other food safety interventions in reducing foodborne pathogens in seafood, dairy products, fruits and vegetables, and to develop future food safety programs.

The Future of FoodNet

For the project to be successful, data must be collected over a number of years to chart national trends and consider the effectiveness of control strategies. The data at this point are very preliminary and cannot be relied upon as an accurate indicator of either the prevalence of foodborne illness or its causes.

Beginning in fiscal year 1998, all sites will participate in a case-control study for Campylobacter infections. Previously, the case-control studies were limited to laboratory-confirmed cases of Salmonella or E. coli O157:H7.

For More Information...

This backgrounder is also available at the FSIS Web site at: http://www.fsis.usda.gov/background/bfoodnet.htm

Additional information about the Foodborne Disease Active Surveillance Network is available at: http://www.fsis.usda.gov/OPHS/fsisrep1.htm

For Further Information Contact:
FSIS Congressional and Public Affairs Staff
Phone: (202) 720-3897
Fax: (202) 720-5704

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