Almost a third of passengers aboard a scenic National Geographic cruise off the coast of Alaska have come down with a grim gastrointestinal infection. Health officials at the Centers for Disease Control confirmed Tuesday that 18 of the Sea Bird vessel’s total 62 passengers are suffering from “abdominal cramps” and “vomiting.” It’s the third such outbreak aboard the 152-foot-long vessel in as many months. The CDC’s Vessel Sanitation Program is “remotely monitoring the situation, including review of the ship’s outbreak response and sanitation procedures,” the agency has said. It comes amid the rapid spread of “explosive diarrhea” across the United States due to an outbreak of the parasite cyclosporiasis.