A US cruise ship has been placed in quarantine by the Caribbean island of St Lucia after a case of measles was reported on board, the island's chief medical officer said.
Dr Merlene Fredericks James said there was a confirmed case of measles on board and "thought it prudent that we quarantine the ship".
No-one aboard was allowed to leave.
The ship is reportedly the Freewinds, which is said to be owned and operated by the Church of Scientology.
Dr Fredericks James said in a video statement posted on YouTube on Tuesday that the ministry learned of the confirmed measles case from "two reputable sources".
She cited the fact that measles was a highly infectious disease as a factor in the decision.
"One infected person can easily infect others through coughing, sneezing, droplets being on various surfaces, etc. So because of the risk of potential infection - not just from the confirmed measles case, but from other persons who may be on the boat at the time - we thought it prudent to make a decision not to allow anyone to disembark."
She also cited the current situation in the US, where cases of the disease are at a 25-year high, as another factor.
NBC News, citing a St Lucia Coast Guard, reported that the boat is the Freewinds, a 440ft (134m) vessel owned and operated by the Church of Scientology, thought to have some 300 passengers on board.
"The ship's doctor has the confirmed case in isolation on the ship," Dr Fredericks James was quoted as saying by NBC. "The individual is in stable condition."
The St Lucian authorities do not have the authority to keep the ship from leaving, and it is currently due to leave the island at 23:59 (03:59 GMT) on Thursday, NBC reports officials as saying.
The ship-tracking website MarineTraffic.com shows a ship called SMV Freewinds docked in Castries, the country's capital.
The Church of Scientology has so far not publicly commented on the case.
Earlier this week, US health officials reported that more than 700 people had been infected by measles this year, marking a 25-year high for cases of the infectious disease in the country.
Cases had been recorded in 22 states and were mostly affecting unvaccinated children, the Centers for Disease Control and Prevention said on Monday.
Officials said the increase in cases is the largest since 1994, including 78 reported in the past week.
Some parents are said to have chosen to leave their children unvaccinated due to the unscientific claim that vaccines cause illnesses such as autism, or on religious grounds.
Most cases occurred in 13 outbreak zones, including in New York City's orthodox Jewish communities.
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