Officials at George Washington University in Washington are alerting the campus that about 85 students have been sickened by the norovirus this week.

University officials said in a statement Wednesday that norovirus was the cause of dozens of cases of gastrointestinal illness. Officials said students who live at the Foggy Bottom campus, the Mount Vernon campus and off campus were affected but that they could not find a common link.

University officials said they contacted the D.C. Department of Health when a large number of students reported the illness.

The reports began trickling in Monday but the majority of cases seen by the university’s student health service have come in the past 24 hours, according to a statement issued by school officials.

The norovirus is responsible for about 90% of epidemic nonbacterial outbreaks of gastroenteritis around the world, and may be responsible for 50% of all foodborne outbreaks of gastroenteritis in the US. It can be contracted through person-to-person contact and the contamination of surfaces like door handles and bathroom counters.

Symptoms of norovirus include nausea, vomiting and diarrhea. The virus is usually not considered serious and most people recover in one or two days.

Students have been advised to wash their hands frequently and disinfect surfaces. The school also said it would beef up cleaning of commonly used areas.