The illness bout that hit a cheerleading championship in Washington State last weekend was caused by a fast-acting gut bug known as norovirus

A spokeswoman for the Snohomish Health District revealed that the illness was caused by norovirus and added that someone entered the competition when sick.
She revealed that janitorial crews were asked to clean vomit from a restroom and on the walkway and suggested that those two places could have acted as exposure sites for the cheer and dance teams. The state health department said that while 229 confirmed cases have been found out so far, the number is expected to grow as the investigation progresses as more than 3,000 people attended the event.
Source-Medindia