The source of a norovirus outbreak in Wisconsin this past spring that sickened 54 people “most likely” was a hotel chef infected with a rare strain of the virus, namely Norovirus genogroup II.17B (Kawasaki), which has only been seen in the United States in the past five years.

That’s according to a Final Investigation Report released Oct. 26 from the Wood County Health Department in Wisconsin Rapids and the Wisconsin Division of Public Health in Madison.

Hotel Marshfield banquet roomThe norovirus outbreak was reported soon after a banquet April 16 at the locally owned Hotel Marshfield in Marshfield, WI, a city of about 20,000 halfway between Minneapolis, MN, and Green Bay, WI.

Initially, 58 of the estimated 276 people who attended the banquet reported becoming ill, although only four of them sought medical attention, according to the report. None visited an emergency room and nobody connected to the outbreak was hospitalized.

“The most frequently reported signs and symptoms among the 51 primary case-patients included fatigue, diarrhea, nausea, muscle aches, body ache, abdominal cramps, vomiting, and sweating,” according to the report.

The ages of those sickened ranged from 21 to 73 years, and they were residents of 13 different states, although 38 lived in Wisconsin. The duration of illnesses was from one to nine days, according to the report.

Five people included in the outbreak cases were employees of the hotel, including the chef.

“The earliest reported illness occurred in a chef and began less than eight hours after the banquet meal,” the investigation report states. The individual is not named in the report and is referred to only as “Chef A.”

“Review of employee work schedules in conjunction with their self-reported illness onset and well dates indicated that Chef A continued to work while symptomatic with norovirus infection,” according to the report.

A case-control study analysis detailed in the report indicated that banquet attendees were 2.59 times more likely to become ill if they consumed an item from the “steak plate,” which consisted of New York strip steak with red wine reduction, buttery garlic chive mashed potatoes and glazed carrots.

Hotel Marshfield signBecause the hotel was short-staffed when the banquet occurred, the report states it “may have contributed to a breakdown in hand hygiene or glove use.” Also, investigators noted that the facility did not have written formal policies at the time regarding glove use, employee illnesses, or hand-washing.

An inspection of the hotel’s kitchen facilities revealed no problems with hot or cold holding or cooking temperatures, according to the report, although concern was noted about the close proximity of employee restrooms to food preparation areas and whether exhaust fans in the restrooms were working.

This situation could allow “aerosolized virus particles generated by toilet flushing after use by an ill employee” to enter kitchen food preparation areas, pulled by the stronger exhaust fans over ovens and grills, and contaminate food items and the kitchen environment, the report states.

Hotel Marshfield management has reportedly addressed the problems identified during the outbreak investigation. In a statement released Oct. 26, Carla Minsky, the hotel’s communication director, said that the facility had cooperated with the investigation and had looked forward to the findings.

(To sign up for a free subscription to Food Safety News, click here.)