About two dozen Union College students have fallen ill with vomiting, diarrhea and nausea over the past few days. The county Health Department is investigating the cause of the outbreak, which has the symptoms of a norovirus.

Union College is on a trimester system, so students are on campus longer than other local colleges. Final exams begin next week and graduation is June 15.

Students began reporting to the school's infirmary on Sunday, but the volume of cases increased Monday evening and Tuesday, said Kathy Sen, supervising community health nurse for communicable disease control for the county.

Three students were transported by ambulance Tuesday from the infirmary to Ellis Hospital, where they were treated and released, said Phil Wajda, spokesman for the college. The students were treated for dehydration, Sen said.

Union College contacted the county health department Tuesday and sent out a campus-wide e-mail warning faculty, students and staff of the illness, Wajda said. The school also began disinfecting common areas and bathrooms.

Norovirus, also known as Norwalk virus, usually causes two days of severe vomiting and diarrhea. Most people recover fully. The virus is highly contagious and notorious for outbreaks on cruise ships. It can be transmitted by contact with a sick person, or through contaminated water or food.

"Union College is great," Sen said. "They picked up on this right away."

There is no obvious link among the students who have fallen ill. They live in different dorms and are in different classes. The county's communicable disease team was on campus Tuesday interviewing students to find any common activities among them.

Tests for bacteria and viral infections were done on the students who went to the hospital. Their symptoms point to a norovirus, Sen said.

Sen advised that ill students should stay hydrated and should avoid anti-diarrheal medications, which will keep the virus in the body longer.

"We are trying to encourage them to stay in their dorm rooms if they are ill and increase their hand washing," she said.