In November 2012, Minnesota Department of Health (MDH), City of St. Paul Environmental Health (CBPEH) and Minnesota Environmental Health (EH) staff investigated an outbreak of norovirus among members of multiple meal parties who ate food prepared by a restaurant in St. Paul. One group of 41 co-workers ate food provided at a retirement party on November 2. Also on November 2, another group of 6 individuals became ill after eating a meal catered by the restaurant. A third group reported illnesses after eating a chopped salad prepared by the restaurant on November 3. A total of 36 patrons from the three groups were interviewed. Twenty-four met the case definition. Stool samples submitted by five ill restaurant patrons tested positive for norovirus GII. Nucleic acid sequencing was conducted on all five positive samples; the nucleic acid sequences were identical.

Among the retirement party attendees, consuming the grilled asparagus with roasted red peppers and kale was significantly associated with illness. A small number of non-ill controls interviewed among the two other groups who reported illness precluded a meaningful analysis of food exposures. However, both groups ordered the chop salad, which was the only food item reported by the majority of cases in both groups.

CBPEH and MDH sanitarians interviewed 157 restaurant employees. Fifteen reported recent gastrointestinal illness. These employees reported becoming ill in October and between November 4 and 13. The restaurant did not have a glove use policy. Given that numerous restaurant employees reported recent gastrointestinal illness, investigators concluded that an infected food worker was the likely source of the outbreak.