Nearly a dozen Republican staffers who are in Cleveland for the Republican National Convention have tested positive for norovirus, public health officials said Wednesday.

Ohio public health officials confirmed reports from Tuesday that a group of staffers from the California delegation had contracted the virus, according to Stat News.

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Those infected with the norovirus were part of the advance team for the California delegation, leading to concerns that the bug may spread.

“It came with them,” Erie County Health Commissioner Peter Schade told Stat News.

But public health officials have taken precautions by quarantining those who were believed to be infected, while warning others who may feel under the weather to stay in their hotels.

The norovirus is a contagious bug that causes severe cases of diarrhea and vomiting.