Authorities on the Dutch Caribbean island of Curacao have declared 290 crew and passengers on board Scientology cruise ship Freewinds measles free but warn a question mark still hangs over 28 others.
Chief epidemiologist Dr Izzy Gerstenbluth said 17 crew members and 11 passengers must remain in isolation until at least Monday when the 12 incubation period for the disease is officially over.
The 134 metre, nine-deck Freewinds is the last surviving vessel from the Church of Scientology's original flotilla of "religious retreats".
The retreats are run by the church's most mysterious and dedicated branch — the Sea Organisation, which requires members to sign billion-year contracts and work 365 days a year for little or no wages.
Dr Gerstenbluth said authorities decided to extend the quarantine period for the 28 because they are still at risk of contracting measles from a Danish crew member who tested positive on April 29.
"The rest of the 318 people who were, in total, on the ship, are free to leave, as they are not a threat to anyone anymore, and they cannot become sick anymore," he said.
The church said in a statement that the health authorities in Curacao, its home port, had acknowledged the Freewinds for its strict isolation protocol, which effectively contained the illness to a single case and prevented it from spreading to others.
The ship was previously quarantined in St Lucia before being turned back to Curacao, where it has been grounded since May 4.
Doctors took blood samples from 277 who did not have proof of vaccination and sent them to the Netherlands.
Dr Gerstenbluth said the female crew member who was infected had been in Europe and arrived April 17 in Curacao with cold symptoms.
She was tested for measles, but had already left for St Lucia by the time the results came back. Officials in Curacao then alerted the government of St Lucia.
Inside the Freewinds
Scientologists aiming for the church's spiritual climax, Operating Thetan Level 8 (or OT8 for short), are sent aboard the Freewinds.
The ship is the only place in the whole organisation that offers the OT8 course, which can set devotees back between $US500,000 ($A714,000) to $US2 million ($A2.86 million) and take years to complete.
The ship is fitted out with five-star restaurants, luxury cabins, a cinema, panoramic sun deck and shiny, state-of-the-art control rooms.
Then there's the glittering Starlight Lounge, where church mascot Tom Cruise famously belted out a rendition of Bob Seger's Old Time Rock and Roll with X Factor contestant Stacy Francis on his birthday.
The lounge features a stylised portrait of church founder, former sci fi writer L Ron Hubbard, wearing a captain's hat behind the stage.
The Mission Impossible actor is not the only celebrity to have spent time on the Freewinds. Katie Holmes, John Travolta and John Travolta's wife Kelly Preston have all celebrated birthdays on board.
Others known to have taken a sail include jazz great Chick Corea, Elvis' daughter Lisa Marie Presley, actors Catherine Bell and Juliette Lewis, as well as longtime Australian devotee Kate Ceberano.
There are also whispers Scientology's leader David Miscavige, whose wife mysteriously vanished from the public eye years ago amid an alleged mental health crisis, is on-board.
"Miscavige turned 59 on Tuesday," former Scientologist Tony Ortega wrote on his cult-busting website The Underground Bunker last week.
"Was he aboard the Freewinds for a birthday party when it was quarantined in St Lucia on Monday morning? We think the chances are low that Miscavige is aboard, but we'd love to know one way or the other."
Former Church executive Tom DeVocht said if the elusive leader was on the ship "he will be micromanaging the crisis, and Scientology will do its best to appear to be co-operating fully with (government officials)."
It's not the first crisis to hit the Freewinds.
In 2006, a Sea Org member reportedly contracted chickenpox, passing it onto at least one other crew member before the infected pair were offloaded at a hotel ashore, according to bombshell claims by Sea Org whistleblower Valeska Paris.
"What I can say is that the Sea Org member who got measles will be in serious trouble," Ms Paris told The Underground Bunker.
"When I was on the Freewinds in 2006, a Sea Org member named Angela got chickenpox. "She passed it to another Sea Org member named Isabel. All crew members were asked if they were vaccinated for chickenpox and if they had had it before.
"There were a handful of us who had never been vaccinated and had never had chickenpox, including myself. It was right before maiden voyage, and we should have been quarantined.
"We all had to have blood tests to confirm whether we were immune or not. I wasn't immune, and there were about four other Sea Org members who were not. The ship's doctor got vaccinations for us, and we were all vaccinated on the ship.
"Then Isabel, Angela and everyone who hadn't had chickenpox were sent ashore to stay in a hotel. Isabel still had chickenpox when she was sent ashore. They were there the entire maiden voyage week and came back after (Scientology leader David) Miscavige left the ship."
Authorities say the source of the latest outbreak, a Dutch woman, boarded the Freewinds in Curacao as a crew member on April 17. She went to the ship's doctor complaining of cold symptoms on April 22 and was immediately isolated from others on board.
A blood sample was taken and sent to nearby Aruba, where officials confirmed it was measles on April 29. By that time the ship had already departed for St Lucia.
Curacao officials alerted their counterparts in St Lucia who quarantined the vessel upon arrival before turning it back to its home port
On May 4, a medical team led by Curacao's chief epidemiologist Dr Izzy Gerstenbluth boarded the Freewinds and examined 216 crew members and 102 passengers — a process that took up most of the weekend.
At least 31 crew members and 10 passengers were able to provide proof of vaccination or immunity, but the remaining 277 were awaiting the results of blood tests being conducted in the Netherlands.
The outbreak has forced Freewinds officials to cancel scheduled trips to Dominica on Friday and Aruba on Sunday.
Measles has sickened more than 700 people in 22 US states this year, with federal officials saying the resurgence is driven by misinformation about vaccines. Symptoms include runny nose, fever and a red-spotted rash.
Most people recover, but measles can lead to pneumonia, brain swelling and even death in some cases.
Symptoms include runny nose, fever and a red-spotted rash. Most people recover, but measles can lead to pneumonia, brain swelling and even death in some cases.
More than 700 people in 22 U.S. states have gotten measles this year, with federal officials saying the resurgence is driven by misinformation about vaccines.