NBC News reports that U.S. health officials are expected to board a Royal Caribbean cruise ship in the Virgin Islands on Sunday to investigate a possible outbreak of highly contagious norovirus that has sickened more than 300 passengers and crew members.

The Explorer of the Seas ship stopped part way through a 10-day cruise from Cape Liberty, N.J., to the Caribbean island of St. Maarten after reports of vomiting and diarrhea, according to the cruise line and the Centers for Disease Control and Prevention.

Some 281 of the 3,050 passengers and 22 of the 1,165 crew members showed symptoms of the fast-spreading infection, according to the CDC’s Vessel Sanitation Program, which monitors cruise ships.