In September 2011, Minnesota Department of Health (MDH) staff conducted an investigation of illnesses reported from 3 separate groups representing 8 households. All had eaten at a restaurant in Chisago City September 18 or 19. Fourteen patrons were interviewed. Nine cases were identified. No one was hospitalized and no one died. Five stool specimens collected from patrons were positive for norovirus GII.4 New Orleans.

Eating a salad from the salad bar was significantly associated with illness (9 of 9 cases vs. 0 of 4 controls; odds ratio, undefined; p=0.001). No other menu items were significantly associated with illness.

All 11 restaurant employees were interviewed. None of the employees reported being ill in the time preceding the complainant meal dates. However, a chef had diarrhea on September 16 and September 20 according to another employee and the staff illness log. The employee was seen by a healthcare provider and diagnosed with diverticulitis. Two employees reported caring for a child who had vomiting onset on September 20. Another chef cared for a family member who became ill with diarrhea, vomiting, and cramping on September 14. Stool samples collected from the restaurant's three chefs were negative for norovirus and common foodborne pathogens.

The environmental assessment at the restaurant noted that salad bar items are prepared in the evening and morning, primarily by the restaurant’s chefs. Other employees help prepare salad bar items
throughout the day as needed. The produce for the salad bar is washed, but the employees do not generally wear gloves during the preparation process.

Investigators attributed the outbreak to bare-hand contact with salad bar items by ill employees or employees with illness in their households.