In March 2013 the Minnesota Department of Health investigated an outbreak of gastrointestinal illness among a group of co-workers who shared a catered lunch on March 5 from a restaurant in Duluth, Minnesota. Eighteen co-workers were interviewed. Seventeen met the case definition. The median incubation period for cases was 11 hours (range 4.5 to 19 hours). Symptoms included diarrhea (n=15), cramps (n=6) and vomiting (n=1). The median duration of illness was 16.5 hours (range 7 to 39 hours). All 17 co-workers ate burritos. Although ingredients for the burritos varied depending on the type, all contained rice and beans. The majority of cases also reported consuming chips (n=13) and salsa (n=15). Two ill patrons submitted stool specimens for viral and bacterial toxin testing. Both specimens were negative for norovirus, Clostridium perfringens toxin, and Bacillus cereus diarrheal toxin.

Sanitarians conducted an environmental assessment at the restaurant on March 6. They identified several issues: the warming unit at the restaurant was not holding beans of rice at proper hot holding temperatures; there was no record of temperatures of the beans or rice after cooking; and there was no record of temperatures of the beans or rice held in the warming unit.

Public health investigators concluded this was a foodborne outbreak of suspected bacterial intoxications associated with consumption of burritos from a restaurant in Duluth. The etiology was not confirmed, but the distribution of symptoms and incubations were characteristic of bacterial intoxications caused by C. perfringens or the diarrheal form of Bacillus cereus. A specific food item was not confirmed but the most plausible explanation for the outbreak was that malfunctioning of the warming unit and improper heating of leftover beans and rice led to amplication of bacteria in either or both of these food items.