In May 2011, public health officials in Minnesota investigated an outbreak of norovirus among people who attended a wedding held outdoors at a park.

Food was provided by a caterer. Investigators obtained a list of wedding attendees and interviewed them about food consumption and illness history. Thirty-two outbreak associated cases were identified. One person was hospitalized overnight. No one died. Three stool specimens from wedding attendees and one stool specimen from an employee at the catering company were positive for norovirus GII.

Food items prepared at the caterer included sliced ham, chicken breasts, garlic mashed potatoes,
California-blend vegetables, Italian pasta, dinner rolls, pickles, butter, coffee, and lemonade. Cookies
and wedding cake were purchased from a bakery in Cold Spring, Minnesota. Tootsie rolls and peanuts were purchased by the wedding party and placed in bowls on the guest tables. Bottled water, beer, and pop were also purchased by the wedding party. All the foods from the caterer were self-serve on a buffet line, except for the head table, for which food was plated and served by the catering staff. By univariate analysis, consuming garlic mashed potatoes (32 of 32 cases vs. 17 of 21 controls; odds ratio [OR], undefined; 95% confidence interval [CI], undefined; p = 0.02) and peanuts (22 of 30 cases vs. 9 of 21 controls; OR, 3.7; 95% CI, 1.1 to 12.3; p = 0.03) were significantly associated with illness.

Illness histories and job duty information were obtained from caterer employees. No employees reported having had gastrointestinal illness previous to or on the implicated meal date. The employee who tested positive for norovirus) became ill with an onset date similar to the
attendees (incubation period from the reception of 36 hours.

Because 60% of interviewed attendees were ill, investigators concluded there likely was extensive contamination of one or more food items. The likely source of contamination was a food worker who might have been exposed to ill household members before preparing the mashed potatoes.