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Preliminary Report: Foodborne Outbreak of Escherichia coli O157:H7 Infections from Hamburgers -- Western United States, 1993

During January 1-29, 1993, 230 persons with culture-confirmed infection with Escherichia coli O157:H7 resulting in bloody diarrhea and, in some cases, hemolytic uremic syndrome (HUS) were reported in the state of Washington. Culture results are pending for 80 others with similar illnesses. Preliminary investigations by public health agencies linked cases to consumption of hamburgers from one fast-food restaurant chain. E. coli O157:H7 has been isolated from epidemiologically implicated lots of ground beef; an interstate recall was initiated by the restaurant on January 18. Meat from the same lots of ground beef had been distributed to at least three other western states in which increased numbers of cases of bloody diarrhea have been reported. CDC, the U.S. Department of Agriculture, state and county health departments, and state agriculture investigators are investigating whether cases of bloody diarrhea in the other states are linked to consumption of meat from the same lots of ground beef and are determining the possible sources of the contaminated meat.

Reported by: Enteric Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases; Div of Field Epidemiology, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: E. coli O157:H7 is an emerging infectious agent first linked to human illness in 1982; its importance as a human pathogen appears to be increasing (1,2). Infection with E. coli O157:H7 may result in a spectrum of illnesses, including mild diarrhea, severe bloody diarrhea (hemorrhagic colitis), HUS often leading to acute renal failure requiring dialysis, and death (3). Infection with this organism has been associated with consumption of contaminated beef and raw milk and through personto-person transmission by the fecal-oral route (2). Measures to prevent transmission include thorough cooking of beef, pasteurization of milk, and careful handwashing with soap. In particular, ground beef should be cooked until it is no longer pink. Diagnosis of E. coli O157:H7 infection in the clinical laboratory setting requires specific culture of stool specimens for the organism on modified MacConkey medium containing sorbitol (4).

Physicians who have patients with severe bloody diarrhea of unknown etiology or HUS should consider infection with E. coli O157:H7 and should request the appropriate cultures be done. This outbreak illustrates how surveillance with rapid reporting and prompt investigation of cases can lead to timely public health action. Physicians and laboratories are encouraged to report cases of E. coli O157:H7 infection to their county and state health departments.


  1. Lederberg J, Shope RE, Oaks SC Jr., eds. Emerging infections: microbial threats to health in the United States. Washington, DC: National Academy Press, 1992.

  2. Griffin PM, Tauxe RV. The epidemiology of infections caused by Escherichia coli O157:H7, other enterohemorrhagic E. coli, and the associated hemolytic uremic syndrome. Epidemiol Rev 1991;13:60-98.

  3. Griffin PM, Ostroff SM, Tauxe RV. Illnesses associated with Escherichia coli O157:H7 infections: a broad clinical spectrum. Ann Intern Med 1988;109:705-12.

  4. March SB, Ratnam S. Latex agglutination test for detection of Escherichia coli serotype O157:H7. J Clin Microbiol 1989;27:1675-7.

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