A gastrointestinal illness has broken out this week on the Radiance of the Seas cruise ship, according to the US Centers for Disease Control and Prevention.

The gastrointestinal outbreak on the Royal Caribbean cruise reignites concerns about health safety on sea voyages, especially on high-traffic tourist routes like the Caribbean.

Over 90 people contracted gastrointestinal illnesses from an unknown source on a week-long Royal Caribbean cruise, the CDC said Wednesday. Both passengers and crew aboard the Radiance of the Seas have experienced vomiting and diarrhea.