Hope College in Holland is expected to remain closed a day longer because of “a growing outbreak of a noro-like virus” there, school officials said. The number of cases of the virus among students, faculty and staff has risen to about 400, according to reports.

All classes, athletic events and other campus activities are cancelled. Facility sanitizing efforts continue. The source of the infection is not known yet, but health and school officials are working to find out. The campus is cleaned thoroughly to eliminate lingering viruses.

Noroviruses cause the stomach flu, also known as gastroenteritis. People infected with the virus usually experience diarrhea, nausea and vomiting. Virus symptoms typically last a couple of days.

“Students who have become infected while away from the campus are advised not to return until they receive permission from college officials,” according to a statement on Hope’s Web site.

There are some simple steps students should take to protect themselves from the contagious norovirus: wash your hands with soap and warm water before eating food and after using the bathroom, stay home from work or school if you are sick, avoid public or crowded places in case of infection.

Becoming infected with norovirus may lead to complications such as dehydration, especially among the young and elderly, and may require medical attention, according to the U.S. Centers for Prevention and Disease Control. People with diarrhea or vomiting should drink plenty of fluids to prevent dehydration. Outbreaks usually include restaurants and catered meals, nursing homes, schools, and vacation settings or cruise ships, according to the CDC.