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November 2, 1994

A Multistate Outbreak of Escherichia coli O157:H7—Associated Bloody Diarrhea and Hemolytic Uremic Syndrome From Hamburgers: The Washington Experience

Author Affiliations

From the Epidemic Intelligence Service and the Division of Field Epidemiology, Epidemiology Program Office (Drs Bell and Baron), and the Foodborne and Diarrheal Diseases Branch, National Center for Infectious Diseases (Drs Griffin and Barrett and Ms Wells), Centers for Disease Control and Prevention, Atlanta, Ga; the Washington State Department of Health, Seattle (Drs Goldoft and Kobayashi and Mr Lewis) and Olympia (Mr Bartelson); the Seattle-King County Department of Public Health, Seattle, Wash (Dr Davis); the Snohomish Health District, Everett, Wash (Ms Gordon); and the Division of Gastroenterology, Department of Pediatrics, University of Washington School of Medicine and the Children's Hospital and Medical Center, Seattle (Dr Tarr). Dr Bell is now with the Hepatitis Branch, Division of Viral and Rickettsial Diseases, Centers for Disease Control and Prevention.

JAMA. 1994;272(17):1349-1353. doi:10.1001/jama.1994.03520170059036

Objective.  —To determine the source of and describe a large outbreak of Escherichia coli O157:H7 infections in Washington State.

Design.  —Case-control study; environmental investigation; provider-based surveillance for E coli O157:H7 infections.

Setting.  —Chain of fast-food restaurants, hospitals, physician offices, local laboratories, and local health departments.

Participants.  —Patients with diarrhea and neighborhood controls. A case was defined as diarrhea with culture-confirmed E coli O157:H7 infection or postdiarrheal hemolytic uremic syndrome (HUS) occurring from December 1, 1992, through February 28, 1993, in a Washington State resident. Controls were age- and neighborhood-matched friends of the first 16 case patients.

Interventions.  —Announcement to the public; recall of implicated hamburger lots.

Main Outcome Measure.  —Abatement of outbreak due to E coli O157:H7.

Results.  —Infection was associated with eating at a fast-food chain (chain A) in the 10 days before symptoms began. Twelve (75%) of 16 case patients but no controls had eaten at chain A (matched odds ratio undefined; lower 95% confidence interval, 3.5; P<.001). In total, 501 cases were reported, including 151 hospitalizations (31%), 45 cases of HUS (9%), and three deaths. Forty-eight patients (10%) had secondary infections. Of the remaining 453 patients (90%), 398 (86%) reported eating at a Washington chain A restaurant; 92% of them reported eating a regular hamburger. The pulsed-field gel electrophoresis pattern of the E coli O157:H7 strains isolated from all regular hamburger lots of a single production date shipped to Washington was identical to that of the strains isolated from patients. Ten (63%) of 16 regular hamburgers cooked according to chain A policy had internal temperatures below 60°C. Public health action removed more than 250 000 potentially contaminated hamburgers, preventing an estimated 800 cases.

Conclusions.  —This E coli O157:H7 outbreak, the largest reported, resulted from errors in meat processing and cooking. Public health surveillance through state-mandated reporting of E coli O157:H7 infection as is carried out in Washington State was critical for prompt outbreak recognition and control. Measures should be developed to reduce meat contamination. Consumers and food service workers should be educated about cooking hamburger meat thoroughly.(JAMA. 1994;272:1349-1353)