A US cruise operator is working to track down hundreds of passengers who disembarked a luxury liner in Cambodia after one traveller was later diagnosed with the deadly new coronavirus.

The Westerdam was at sea for two weeks during which it was barred from Japan, Guam, the Philippines, Taiwan, and Thailand over fears it could be carrying the virus, which originated in China and has killed nearly 1,800 people.

Cambodia, a staunch ally of Beijing, allowed the ship to dock Thursday at its southern coastal town of Sihanoukville, with authorities carrying out temperature checks on passengers before they left the ship to catch flights home.

But Thai authorities on Monday said any of Westerdam's passengers transiting through the country will face "severe measures", like getting screened upon entry and exit by health officials.

One traveller from the vessel was stopped Saturday on arriving in Malaysia after airport staff detected a fever. She was later diagnosed with the coronavirus.

The Westerdam cruise ship has been allowed to dock in Cambodia after being barred by Japan, Guam, the Philippines, Taiwan and Thailand
The Westerdam cruise ship has been allowed to dock in Cambodia after being barred by Japan, Guam, the Philippines, Taiwan and Thailand AFP / TANG CHHIN Sothy

The 83-year-old American woman is under observation at a hospital while her husband, 85, is also being monitored.

Some 137 passengers from the Westerdam who also took the Malaysia flight with the American have now left on commercial flights for other destinations.

Cruise operator Holland America said Sunday it was in "close coordination" with Malaysian and Cambodian officials alongside experts from the World Health Organization and the US Centers for Disease Control and Prevention.

The company is working with "national health authorities to investigate and follow up with individuals who may have come in contact with the guest", said Dr Grant Tarling, the operator's chief medical officer.

The Westerdam cruise ship remains docked at Cambodia's southern coastal town of Sihanoukville
The Westerdam cruise ship remains docked at Cambodia's southern coastal town of Sihanoukville AFP / TANG CHHIN Sothy

Another 233 passengers and 747 crew remain on the Westerdam, which is still docked at Sihanoukville. Authorities have been allowing them to leave the vessel in groups based on their flight bookings but those on board told AFP they are now not permitted to disembark.

A Sihanoukville spokesman said Monday health samples are being collected from all onboard the Westerdam "in order to be clear", adding that passengers will not go off-ship until the tests are completed.

Other passengers who have already left the ship are in Phnom Penh waiting for flights home.

A tweet by passenger Christina Kerby said Cambodia's health ministry had instructed them to stay in their hotel rooms.

She posted light-hearted updates when onboard the Westerdam, but on Monday said she panicked when being tested for the coronavirus by "doctors in moon suits".

"It opened my eyes to the severity and harsh reality of this public health crisis," Kerby tweeted.

Officials in neighbouring Thailand, which had barred the Westerdam from docking, said passengers transiting through its airports will face strict measures.

They would be screened by the airlines and officials at every part of the journey, Suwanchai Wattanajingcharoenchai of the Thai Department of Disease Control said.

For those who want to remain in Thailand, they would need permission from the embassy in Phnom Penh.

"The foreigners... will be quarantined for 14 days," he added.

In China more than 70,000 people have been infected with the coronavirus while about 780 infections have been reported in other countries.

Cambodia's decision to allow the Westerdam to berth was lauded by US President Donald Trump, who called the country "beautiful" on Twitter, and US ambassador Patrick Murphy boarded the ship to greet its American passengers.