Multistate outbreak of Escherichia coli O157:H7 infection associated with consumption of packaged spinach, August-September 2006: the Wisconsin investigation

Abstract

Background: Escherichia coli O157:H7 infection often causes hemorrhagic colitis and hemolytic uremic syndrome.

Methods: In 2006, the Wisconsin Division of Public Health and the Wisconsin State Laboratory of Hygiene, in cooperation with other local, state, and federal partners, investigated an outbreak of E. coli O157:H7 infection.

Results: In September 2006, the Wisconsin Division of Public Health and the Wisconsin State Laboratory of Hygiene were able to link geographically dispersed E. coli O157:H7 isolates recovered from the stool samples of ill persons, all of which had the same pulsed-field gel electrophoresis pattern (i.e., outbreak pattern). Investigators conducted a case-control study with control subjects (n = 86) matched to case patients (n = 49) by age, sex, and residential location. All case patients' onsets of illness occurred during the period from 20 August through 14 September 2006. Illness was associated with spinach consumption (matched odds ratio, 82.1; 95% confidence interval, 14.7 to >1000). Of the 49 case patients, 26 (53%) recalled eating brand A spinach. On multibrand analysis, only brand A was associated with illness (undefined matched odds ratio; 95% confidence interval, 6.8-infinity). Wisconsin's agriculture laboratory isolated E. coli O157:H7 with the outbreak pattern from spinach in 2 brand A packages, both produced on 15 August 2006.

Conclusions: The rapid multijurisdictional epidemiologic and laboratory response, including timely pulsed-field gel electrophoresis pattern analysis and PulseNet posting, facilitated prompt voluntary recall of brand A spinach.