On January 13, 1993, the Washington Department of Health (WDOH) was notified that a cluster of children suffering hemolytic uremic syndrome (HUS) secondary to E. coli infection was being treated in a Seattle-area hospital and that there had been an increase in emergency room visits from patients with bloody diarrhea. In response to the apparent outbreak, WDOH began interviewing case-patients for an epidemiologic investigation and learned that nearly all patients had consumed hamburgers purchased from Jack in the Box restaurants in the days before becoming ill.
The WDOH E. coli outbreak investigation led to the discovery that regular-sized hamburger patties and “jumbo” hamburger patties produced by Von Companies of California and sold by Jack in the Box were the source of the E. coli outbreak. The outbreak strain of E. coli O157:H7 was isolated from 11 lots of patties produced on November 29 and 30, 1992, and Jack in the Box issued a recall of all ground beef produced on that day that was still in restaurants. About 20 percent of the implicated ground beef was recovered through the recall.
Since the ground beef identified as the source of the outbreak had been distributed to Jack in the Box restaurants in Washington, Idaho, California, and Nevada, all states investigated cases of bloody diarrhea that had been reported since November 15, 1992 to determine whether patients had eaten hamburgers from Jack in the Box in the days before becoming ill. By the end of February 1993, the states had reported the following:
• Washington reported 602 patients with bloody diarrhea or HUS. 477 Washingtonians were culture-confirmed with E. coli infections, with illness onset peaking between January 17 and January 20, 1993. 144 people were hospitalized; 30 developed HUS, and three died.
• Idaho reported 14 culture-confirmed E. coli O157:H7 cases with illness onset dates between December 11, 1992 and February 16, 1993. Four people were hospitalized; one developed HUS
• California reported six culture-confirmed cases, with 34 patients meeting the outbreak-case definition with illness onset dates between November 15 1992 and January 31, 1993. Fourteen people were hospitalized; seven developed HUS, and one child died.
• Nevada reported only one culture-confirmed case, with 58 other patients meeting the outbreak-case definition with illness onset dates between December 1, 1992 and February 7, 1993. Nine people were hospitalized; three developed HUS.
Seventy-three Jack in the Box restaurants were ultimately identified as part of the outbreak and recall. A trace-back was conducted, and five slaughter plants in the United States and one in Canada were identified as the likely sources of beef used by Von’s Corporation in the production of the hamburger patties sold to Jack in the Box. No one slaughter plant or farm was ever identified as the source.