Background: Escherichia coli O157:H7 is a Shiga toxin-producing E. coli (STEC) associated with numerous foodborne outbreaks in the United States and is an important cause of bacterial gastrointestinal illness. In May 2009, we investigated a multistate outbreak of E. coli O157:H7 infections.
Methods: Outbreak-associated cases were identified using serotyping and molecular subtyping procedures. Traceback investigation and product testing were performed. A matched case-control study was conducted to identify exposures associated with illness using age-, sex-, and state-matched controls.
Results: Seventy-seven patients with illnesses during the period 16 March-8 July 2009 were identified from 30 states; 35 were hospitalized, 10 developed hemolytic-uremic syndrome, and none died. Sixty-six percent of patients were <19 years; 71% were female. In the case-control study, 33 of 35 case patients (94%) consumed ready-to-bake commercial prepackaged cookie dough, compared with 4 of 36 controls (11%) (matched odds ratio = 41.3; P < .001); no other reported exposures were significantly associated with illness. Among case patients consuming cookie dough, 94% reported brand A. Three nonoutbreak STEC strains were isolated from brand A cookie dough. The investigation led to a recall of 3.6 million packages of brand A cookie dough and a product reformulation.
Conclusions: This is the first reported STEC outbreak associated with consuming ready-to-bake commercial prepackaged cookie dough. Despite instructions to bake brand A cookie dough before eating, case patients consumed the product uncooked. Manufacturers should consider formulating ready-to-bake commercial prepackaged cookie dough to be as safe as a ready-to-eat product. More effective consumer education about the risks of eating unbaked cookie dough is needed.