WASHINGTON (CBSDC) — School officials at Howard University say they’re treating a number of cases of the Norovirus that is turning up.

About 85 cases turned up at George Washington University last week, as well as at least one case a Prince William County elementary school. Also 186 cases were reported at Rider University and about 100 at Princeton University, both in New Jersey. It has also hit passengers on at least three cruise ships.

One in 15 Americans every year are affected by norovirus, causing sudden vomiting, diarrhea and stomach cramps that continue for a very unpleasant 24 to 48 hours.

Students are being asked to take precautions to avoid getting the virus. Tips range from washing your hands a lot, especially when handling food to cleaning contaminated surfaces.