The Royal Caribbean International's Explorer of the Seas is docked at Charlotte Amalie Harbor in St. Thomas, U. S. Virgin Islands, Sunday, Jan. 26, 2014. U.S. health officials have boarded the cruise liner to investigate an illness outbreak that has stricken at least 300 people with gastrointestinal symptoms including vomiting and diarrhea. (AP Photo/Thomas Layer)

The Royal Caribbean International's Explorer of the Seas is docked at Charlotte Amalie Harbor in St. Thomas, U. S. Virgin Islands, Sunday, Jan. 26, 2014. U.S. health officials have boarded the cruise liner to investigate an illness outbreak that has stricken at least 300 people with gastrointestinal symptoms including vomiting and diarrhea. (AP Photo/Thomas Layer)