Overland Park ? Johnson County health officials say they don’t know how more than half of the students at an Overland Park elementary school contracted a contagious virus that caused classes to be canceled last week.

The Johnson County Health Department says 186 students and 12 staff members were missed school Thursday after being exposed to a highly contagious nolovirus that causes gastroenteritis. The Kansas City Star reports it’s the same kind of virus that has made the news by affecting cruise ships.

Classes at Trailwood Elementary school were canceled Friday so the school could be thoroughly cleaned.

The virus cannot be treated by antibiotics, lasts one or two days and typically includes vomiting and diarrhea.