A MULTISTATE OUTBREAK OF ESCHERICHIA-COLI-O157-H7 ASSOCIATED BLOODY DIARRHEA AND HEMOLYTIC-UREMIC-SYNDROME FROM HAMBURGERS - THE WASHINGTONEXPERIENCE

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 surveillan ce for E coli O157:H7 infections. Setting.-Chain of fast-food restaura nts, hospitals, physician offices, local laboratories, and local healt h departments. Participants.-Patients with diarrhea and neighborhood c ontrols. A case was defined as diarrhea with culture-confirmed E coli O157:H7 infection or postdiarrheal hemolytic uremic syndrome (HUS) occ urring from December 1, 1992, through February 28, 1993, in a Washingt on State resident. Controls were age- and neighborhood-matched friends of the first 16 case patients. Interventions.-Announcement to the pub lic; recall of implicated hamburger lots. Main Outcome Measure.-Abatem ent of outbreak due to E coli O157:H7. Results.-Infection was associat ed with eating at a fast-food chain (chain A) in the 10 days before sy mptoms began. Twelve (75%) of 16 case patients but no controls had eat en at chain A (matched odds ratio undefined; lower 95% confidence inte rval, 3.5; P<.001). In total, 501 cases were reported, including 151 h ospitalizations (31%), 45 cases of HUS (9%), and three deaths. Forty-e ight patients (10%) had secondary infections. Of the remaining 453 pat ients (90%), 398 (86%) reported eating at a Washington chain A restaur ant; 92% of them reported eating a regular hamburger. The pulsed-field gel electrophoresis pattern of the E coli O157:H7 strains isolated fr om all regular hamburger lots of a single production date shipped to W ashington 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 degrees C. Public health action re moved more than 250 000 potentially contaminated hamburgers, preventin g an estimated 800 cases. Conclusions.-This E coli O157:H7 outbreak, t he largest reported, resulted from errors in meat processing and cooki ng. Public health surveillance through state-mandated reporting of E c oli O157:H7 infection as is carried out in Washington State was critic al for prompt outbreak recognition and control. Measures should be dev eloped to reduce meat contamination. Consumers and food service worker s should be educated about cooking hamburger meat thoroughly.