All 46 schools will be shut down on Thursday, Nov. 21, and Friday, Nov. 22, in a Grand Junction school district as an unknown virus continues to spread among students and district employees.

After the Thanksgiving break next week, the Mesa County Valley School District 51 will reopen.

“We are taking this highly unusual action because this virus is extremely contagious and spreading quickly across our schools,” coordinator for District Nursing Tanya Marvin said in a news release.

However, there now appears to be a second associated virus that affects students, some of whom have already been ill in recent weeks. The two combined have produced an alarming spread of disease.

Earlier this week, four schools–Rocky Mountain Elementary, Juniper Ridge Community School, Palisade High School, and Mount Garfield Middle School–had been confirmed by the district because of the virus, which has caused quickly developing symptoms of vomiting. County health officials said they’re still working to identify the disease.

During the closing, the custodial crews of the school district will work to disinfect the schools.