Unknown to most in public health in late December 1992, the San Diego County Department of Health Services was notified of a child with E. coli O157:H7 infection who subsequently died (Lauren Rudolph). Active surveillance and record review then identified eight other persons with E. coli O157:H7 infections or HUS from mid-November through mid-January 1993.  

However, E. coli O157:H7 was not a reportable infectious disease in California and therefore public health official in California, Washington and at the federal level were unaware of the cluster of illnesses that essentially predated the largest part of the outbreak.  Had it been reportable, it is most likely the E. coli O157:H7 outbreak would have been contained in California.

That was not to be the case; from November 15, 1992, through February 28, 1993, more than 600 laboratory-confirmed infections with E. coli O157:H7 and four associated deaths occurred in four states — Washington, Idaho, California, and Nevada. Of the patients, more than 150 were hospitalized; over 30 developed HUS, and four died. The median age of patients was 7.5 years (range: 0-74 years).

On January 13, 1993, a physician reported to the Washington Department of Health a cluster of children with hemolytic uremic syndrome (HUS) and an increase in emergency room visits for bloody diarrhea. During January 16- 17, a case-control study comparing 16 of the first cases of bloody diarrhea or Postdiarrheal HUS identified with age- and neighborhood-matched controls implicated eating at chain A (Jack-in-the-Box) restaurants during the week before symptom onset. On January 18, a multistate recall of unused hamburger patties from Jack-in-the-Box restaurants was initiated. E. coli O157:H7 was a reportable infectious disease in Washington.

During the outbreak, Jack-in-the-Box restaurants in Washington linked with cases primarily were serving regular-sized hamburger patties produced on November 19, 1992; some of the same meat was used in “jumbo” patties produced on November 20, 1992. The outbreak strain of E. coli O157:H7 was isolated from 11 lots of patties produced on those two dates; these lots had been distributed to restaurants in all states where illness occurred. Approximately 272,672 (20%) of the implicated patties were recovered by the recall.

A meat traceback by a CDC team identified five slaughter plants in the United States and one in Canada as the likely sources of carcasses used in the contaminated lots of meat and identified potential control points for reducing the likelihood of contamination. The animals slaughtered in domestic slaughter plants were traced to farms and auctions in six western states.