Risk Assessment of E. coli O157:H7 in Ground Beef
E. coli O157:H7 was first recognized as a human pathogen in 1982, when it was associated with two outbreaks of bloody diarrhea in Oregon and Michigan involving the consumption of hamburgers from a fast-food chain. Since then, E. coli O157:H7 has become a public health concern worldwide, causing outbreaks in the United States, Japan, Canada, Scotland, and Argentina. In 1999, the Centers for Disease Control and Prevention (CDC) estimated that 76 million foodborne illnesses occur annually in the United States. An estimated 62,000 cases of symptomatic E. coli O157:H7 infections occur annually in the United States due to foodborne exposures, resulting in approximately 1,800 hospitalizations and 52 deaths. As many as 3,000 cases may develop hemolytic uremic syndrome annually. Surveillance data indicate that the highest incidence of illness from E. coli O157:H7 occurs in children under 5 years of age.
Since 1982 (when E. coli O157:H7 emerged as a foodborne pathogen in the United States), FSIS has taken several regulatory measures to protect public health against this pathogen. In August 1994, FSIS declared E. coli an adulterant. Under this policy, raw chopped or ground beef products that contain E. coli O157:H7 required further processing to destroy E. coli O157:H7. On October 17, 1994, FSIS initiated a microbiological testing program for E. coli O157:H7 in raw ground beef in meat plants and retail stores. The initial testing program was established and designed to test approximately 5,000 raw ground beef samples, 50% from federally inspected plants and 50% from retail stores. In 1998, the sample size was increased from 25 grams to 325 grams to increase test sensitivity for this organism.
In addition to improved sampling for E. coli O157:H7 in ground beef, FSIS initiated a risk assessment of E. coli O157:H7 in March 1998. The goal was to produce a baseline risk assessment that reflects current practices along the farm-to-table continuum and accurately assesses the likelihood of human morbidity and mortality associated with the consumption of ground beef contaminated with E. coli O157:H7 in the United States.
The primary use of this risk assessment is to assist FSIS in reviewing and refining its risk reduction strategy for E. coli O157:H7 in ground beef. The risk assessment produces scientific support for the development of regulatory impact assessments to support FSIS rulemaking, the identification of critical control points and critical control limits in Hazard Analysis and Critical Control Point (HACCP) systems for ground beef, risk-based sampling plans for FSIS inspectors to verify that industry HACCP systems are meeting regulatory standards for E. coli O157:H7 in ground beef, and the identification of food safety research on E. coli O157:H7 in ground beef.
FSIS has based the risk assessment of E. coli O157:H7 in ground beef on a comprehensive review of the available literature and data. This risk assessment includes data available through July 2001. The baseline risk assessment follows the generally accepted framework for microbial risk assessments with four primary components: (1) hazard identification, (2) exposure assessment, (3) hazard characterization, and (4) risk characterization (Figure 1). The result of the risk assessment is a computer model that can be refined and updated for use in future risk assessments for ground beef products as new information and data become available.