(Reuters) - Two more cases of norovirus were confirmed in people who visited a Buffalo Wild Wings Inc restaurant in Kansas, but the source of the illness could not be identified, a spokeswoman for the state health department's county office said.
Now, a total of three people out of the 10 people who were tested are confirmed to have contracted norovirus, the Johnson County Department of Health and Environment spokeswoman said.
There have been no other reports of illness related to the Buffalo Wild Wings' restaurant in Overland Park in suburban Kansas City, Johnson County spokeswoman Barbara Mitchell told Reuters in an email.
"We have taken additional steps to conduct deep cleaning for norovirus at all Kansas City area restaurants," Buffalo Wild Wings, known for its chicken wings, said on Friday.
News of the illness and subsequent investigation broke days before the Super Bowl, one of the biggest nights for the restaurant chains. The company sold more than 11 million traditional and boneless wings during the Super Bowl last year.
Norovirus is the most common cause of food-borne disease outbreaks in the United States and infections usually occurs in places such as hospitals, cruise ships and universities, where people eat and live in close quarters.
Last year, two norovirus outbreaks were reported at the Massachusetts and California outlets of popular burrito chain operator Chipotle Mexican Grill Inc.
About 19 million to 21 million norovirus cases, with 570 to 800 related deaths, are reported in the United States each year, according to the U.S. Centers for Disease Control and Prevention.
Buffalo Wild Wings' shares were marginally higher at $143.85 in midday trading on Friday. Up to Thursday' close, the stock had fallen about 10 percent this year.
Reporting by Subrat Patnaik in Bengaluru; Editing by Kirti Pandey and Savio D'Souza