GREELEY, Colo. — Five schools in Greeley will be closed on Friday after a norovirus outbreak that has "infected a significant number of students and staff."

Scott Elementary School, Madison Elementary School, Jefferson Junior High School, Franklin Middle School and the Transitions Program at the former Cameron Elementary School will be closed in an effort to stop the spread of the illness, according to a press release from the Greeley School District. All after-school activities have also been canceled. 

According to a release from the Greeley School District, a "larger-than-usual number of sick students" was first reported at Franklin Middle School on Feb. 22.

That's when the Weld County Health Department was called in to consult with District 6 staff. District 6 cleaning crews cleaned and disinfected the school over the weekend, and have been cleaning and disinfecting with additional personnel every night this week. 

However, more than 100 students were reported sick Wednesday with a number having to be sent home during the school day. Several staff members are sick as well.

Franklin Middle School closed on Thursday.

That same day, Scott Elementary School, Madison Elementary School, Jefferson Junior High School and the Transitions Program at the former Cameron Elementary School each reported a "larger-than-usual number of sick students, the release says.

“We have been in consultation with the Weld County Health Department and have followed the cleaning protocols and health precautions that have been recommended,” Superintendent Dr. Deirdre Pilch said. “Despite all our efforts, the norovirus continues to impact a significant number of students and staff. We believe closing the school Thursday and Friday will help those who are infected to recover and help stop the spread of the virus.”

The incubation period for norovirus is up to 48 hours, which means people can be carrying the virus, spreading the virus and have no symptoms.

Norovirus is also a highly contagious, hard-to-kill virus that takes very specific procedures and time to eliminate.

All of the schools will reopen Monday, March 4. Extra cleaning crews will work over the next few days to again disinfect every surface in the building. Staff will not be allowed to access the building during the closure.

Widespread illness also closed a Denver school on Friday. The district did not provide specifics about what the illness is.

RELATED: Widespread illness shuts down Denver elementary school

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