A Church of Scientology cruise ship has been quarantined near the Caribbean island nation of St. Lucia after a case of measles was confirmed on board. The ship’s 300 passengers and crew members were ordered to remain inside after a female crew member was found to have contracted the disease Monday. “We thought it prudent that we quarantine the ship,” said Merlene Fredericks-James, St. Lucia’s chief medical officer. According to the church’s official website, the ship is the home of the Flag Ship Service Organization (FSSO), a “religious retreat ministering the most advanced level of spiritual counseling in the Scientology religion.” The Church of Scientology has not publicly discouraged its members from getting vaccines, but the organization is strongly opposed to some forms of Western medicine, specifically psychiatry. There have been 704 measles cases reported so far this year in the U.S.—the most in 25 years—with the number surging 43 percent in just two weeks last month. The increase is attributed to the anti-vaccination movement, which promotes inaccuracies about vaccines.