Background: Escherichia coli O157:H7 infections have traditionally been associated with animal products, but outbreaks associated with produce have been reported with increasing frequency. In fall 1996, a small cluster of E. coli O157:H7 infections was epidemiologically linked to a particular brand (brand A) of unpasteurized apple juice.
Objective: To define the extent of the outbreak, confirm the source, and determine how the apple juice became contaminated.
Design: Descriptive epidemiologic study and traceback investigation.
Setting: Western United States and British Columbia, Canada.
Patients: Patients with E. coli O157:H7 infection who were exposed to brand A apple juice.
Measurements: Clinical outcome and juice exposure histories of case-patients, pulsed-field gel electrophoresis of case and juice isolates, and juice production practices.
Results: Seventy persons with E. coli O157:H7 infection and exposure to brand A unpasteurized apple juice were identified. Of these persons, 25 (36%) were hospitalized, 14 (20%) developed the hemolytic uremic syndrome, and 1 (1%) died. Recalled apple juice that was produced on 7 October 1996 grew E. coli O157:H7 with a pulsed-field gel electrophoresis pattern indistinguishable from that of case isolates. Apple juice produced on 7 October 1996 accounted for almost all of the cases, and the source of contamination was suspected to be incoming apples. Three lots of apples could explain contamination of the juice: Two lots originated from an orchard frequented by deer that were subsequently shown to carry E. coli O157:H7, and one lot contained decayed apples that had been waxed.
Conclusions: Standard procedures at a state-of-the-art plant that produced unpasteurized juices were inadequate to eliminate contamination with E. coli O157:H7. This outbreak demonstrated that unpasteurized juices must be considered a potentially hazardous food and led to widespread changes in the fresh juice industry.