The Knox County School Districts kindergarten through 12th grade classes dismissed at 1:15 p.m. Friday.
A number of students became ill with a stomach flu known as the norovirus , school nurse Kathy Palmer said Friday.
At least eight students became ill on Wednesday, but an 50 of the district's 475 students showed symptoms of the illness Friday. The decision was made to dismiss school early in order to combat the continued spread of the virus.
The Edina, Mo.-based school will remain closed Monday so that custodial workers can disinfect the building.
"We've closed two other times over the years for influenza," Palmer said. "This is the first time we've closed for the stomach flu."
The most common symptoms of acute gastroenteritis are diarrhea, vomiting, and stomach pain, according to the Center for Disease Control .
"Norovirus can spread quickly from person to person in crowded, closed places like long-term care facilities, daycare centers, schools, hotels, and cruise ships. Noroviruses can also be a major cause of gastroenteritis in restaurants and catered-meal settings if contaminated food is served," the CDC says.
To stop the spread of norovirus, practice proper hand hygiene, was raw foods carefully before preparation, don't prepare food while you are sick and disinfect hard surfaces where the virus can lie dormant.