(CNN) -- A quarantined cruise ship reportedly owned by the Church of Scientology has a confirmed case of measles onboard, according to health authorities in St. Lucia.
The confirmed case involves a female crew member, Chief Medical Officer Dr. Merlene Fredericks-James said, but "given the highly infectious nature of the disease, it is likely that others may have been exposed."
After learning earlier through two reputable sources that someone on board might have measles, health officials ordered the ship to stay in port to prevent the spread of the disease. No one on the ship has been allowed to disembark.
On Thursday, the ship's doctor requested 100 doses of the measles vaccine, according to a statement from the Department of Health and Wellness, "and this is currently being provided from our supplies, at no cost."
Crew members and passengers are being monitored by the ship's doctor, the statement said. "Continued surveillance is necessary as the incubation period for measles ranges from 10 to 12 days before symptoms in exposed persons occur," the statement added.
The ship has approximately 300 crew members and passengers, Fredericks-James said.
The vessel, named "Freewinds," is still moored there, St. Lucia Coast Guard Sgt. Victor Theodore told NBC News.
The St. Lucia Times posted an image of the ship Wednesday and a marine tracking website showed the ship in Port Castries on the Caribbean island on Thursday afternoon.
The ship arrived at St. Lucia on Tuesday and was set to depart Thursday, according to a schedule posted on the St. Lucia Air and Sea Ports Authority website.
"The ship is free to leave our ports at anytime," Fredericks-James said, adding she did not have information regarding the ship's next port of call or when it planned on leaving.
"Whilst they are in port, we will continue to support them as needed," she said.
The Church of Scientology didn't respond to CNN's request for comment. It says on its website the ship is a religious retreat at the pinnacle of a Scientologist's spiritual journey.
Depending on when other passengers were exposed, it may not be too late for them to receive a measles vaccine.
According to Tim Moody, former chairperson of Emerging Public Health Threats and Emergency Response Coalition, someone who was never vaccinated for and then exposed to measles has 72 hours to receive a vaccine. If they have already caught the disease, the vaccine should reduce the severity.
Using quarantines to assist in controlling an outbreak, while uncomfortable, is an important public health option, Rebecca Katz, who directs the Center for Global Health Science and Security at Georgetown University, told CNN.
"Quarantine is a word that people respond to very strongly, but it's actually one of the strongest tools in the public health tool kit," Katz said. "But because it curtails civil liberties, most public health officials are very wary to utilize it."
Every state has laws in place that allow quarantines and other public health enforcement tools, and they differ based on the jurisdiction. For anyone who refuses to cooperate, actions can range from issuing a self-isolation order to "checking in once a day via the internet, to putting a tracking device on somebody, to placing an armed guard outside of their home," Katz said.
"Sometimes people feel like they're being treated like a criminal," Katz added. "The point is to be treated like you're doing something that is contributing to your society and only be treated like a criminal if you disobey."
Fredericks-James previously said health officials were using authority given to them by the nation's quarantine act and public health act.
Measles is a highly contagious disease caused by a virus that can spread through the air when an infected person coughs or sneezes or if someone comes into direct contact or shares germs by touching the same objects or surfaces. Symptoms may include fever, cough, runny nose, watery eyes and a rash of red spots.
Measles cases in the United States have surpassed the highest number on record since the disease was declared eliminated nationwide in 2000.
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