In early December 2012, Minnesota Department of Health (MDH) epidemiologists investigated an outbreak of norovirus among attendees of several events culminating in a reception held at a restaurant on December 1. A family holiday party at a private home held November 25 and a rehearsal dinner at a community center held on November 30, preceded the reception. A total of 85 attendees were interviewed; 38 (45%) met the case definition. All attendees were asked about attendance at the holiday party and the rehearsal dinner. Neither of these events were significantly associated with illness. The only event all cases reported attending was the reception held on December 1.

Thirty-seven cases reported diarrhea, 29 cases reported vomiting. No cases were hospitalized, and no one sought medical attention. Two attendee stool specimens tested positive for norovirus GII, including a specimen from an attendee who had illness onset on November 30.

The food for the reception was prepared by the restaurant. The dinner was served buffet-style at two locations. Cake from a grocery store in Austin, Minnesota was served and ham sandwiches were available later in the evening. Snacks were available on tables. These snacks were prepared by an individual who had onset of vomiting and diarrhea on November 30 while she prepared the snacks. In univariate anlaysis, consuming au gratin potatoes from a downstairs buffet, ice, and drinks from the bar were significantly associated with illness.

The food for the reception was prepared by the restaurant. An inspector from the MDH sanitarians interviewed employees of the restaurant. Four employees reported recent gastrointestinal illness, including one food worker who reported onset of diarrhea on November 28 and recovery on November 29. This employee's work duties on December 1 included set-up for the event and assembling salads, au gratin potatoes and baked chicken. The remaining three ill food workers had onset of symptoms on December 3. One specimen from a food worker was positive for norovirus GII. Nucleic acid sequencing was conducted on norovirus positive samples from attendees and the food worker. The nucleic acid sequences were identical. The food worker reporting onset of illness before the event did not test positive for norovirus.

Based on the statistical analysis of food items consumed, an infected food worker was the primary source of contamination. However, some of the cases could have occurred due to person-to-person transmission from ill attendees, or from consumption of foods contaminated by i ll or recently ill wedding attendees.