(Bloomberg) -- As passengers from the shunned cruise liner Westerdam fan out toward home following two weeks in limbo at sea, health authorities around the world are mobilizing to prevent a further spread of the coronavirus after an American guest from the ship was found to be infected.

Cruise operator Holland America Line, which gave assurances that the pathogen that’s killed more than 1,700 had not struck anyone aboard the Westerdam, now says it’s working with authorities to deal with the possible fallout from returning guests who may have been exposed to the virus. Passengers hailed from 41 countries and territories, with the largest number from the U.S.

From the Netherlands to Thailand, health authorities are implementing procedures, from quarantines in government facilities to check-ins with public health workers, to deal with the travelers and the risk they pose if they have been infected.

“There may be other people from the ship who have acquired the infection, didn’t show symptoms, yet are now returning home,” said Ben Cowling, a professor of epidemiology at Hong Kong University. “Now that there’s a confirmed case, putting people who return home in quarantine is a natural and reasonable thing to do.”

The plight of the Westerdam, which garnered sympathy on social media after being turned away by five countries and territories, turned into a public health fiasco hours after Cambodia’s Prime Minister Hun Sen welcomed the passengers at the dock and his health ministry cleared them to disembark.

The ship’s saga marks a fresh blow to Asia’s nascent cruise industry, coinciding with an alarming increase in infections on Carnival Corp.‘s Diamond Princess, quarantined in Yokahama, Japan.

Malaysia, Thailand and Singapore said they would no longer allow Westerdam passengers to transit through their airports. The clearing of the bulk of the 1,455 passengers for travel after a self-reported health questionnaire and temperature check has raised tensions among some of Cambodia’s neighbors in Southeast Asia. Twenty passengers had also tested negative for the coronavirus in Cambodia before the ship was cleared.

“The deputy prime minister who leads the national emergency response council -- she has already announced that we are not allowing any flights from Cambodia that have any passengers from Westerdam,” said Ong Kian Ming, deputy minister at Malaysia’s Ministry of International Trade and Industry. “So I think that is sending a signal to the authorities in Cambodia.”

Diamond Princess

The U.S. evacuated 300 Americans from the Diamond Princess, including 14 who tested positive for the virus but showed no symptoms. Japan said infections from the ship jumped to 454 after 99 new cases were identified.

Thailand, the last country to turn the Westerdam away, said it will subject returnees to a 14-day quarantine and also give them the option of a self-quarantine.

“The ship is considered high-risk because people are in close contact with one another for an extended period of time,” said Subhuman Karnchanapimai, the Health Ministry’s permanent secretary. “Just look at what happened with Diamond Princess.”

The Westerdam’s lone infection so far is an 83-year-old American woman who was cleared to travel from Cambodia. After she and more than 100 other Westerdam passengers arrived in Malaysia on Feb. 14 to transit, she came down with a fever, cough and had difficulty breathing. Two tests confirmed the coronavirus diagnosis. Her 85-year-old husband tested negative as did six other passengers. She is in stable condition at a hospital in Kuala Lumpur.

In Cambodia, Holland America -- owned by Carnival -- is now working to manage an escalating public relations crisis. Passengers were told that their returns home would be delayed as Cambodian authorities went back to conduct coronavirus testing on all remaining passengers in the country, the operator said on its blog.

Tests for 406 Westerdam passengers in transit in a hotel in Phnom Penh came back negative, clearing them for travel home, while authorities conduct tests on 255 guests and 747 crew members still aboard the liner, according to the cruise operator.

The World Health Organization is advising Cambodia’s health ministry, and the U.S. Centers for Disease Control and Prevention is also on the ground in Sihanoukville, where the ship is docked. There were about 650 Americans aboard. The ship departed Feb. 1 from Hong Kong with 2,257 passengers and crew.

“We are in close coordination with some of the leading health experts from around the world,” said Dr. Grant Tarling, chief medical officer for Holland America Line. “These experts are working with the appropriate national health authorities to investigate and follow-up with any individuals who may have come in contact with the guest.”

It’s a good sign that a nearly a third of the ship’s passengers have now been tested and do not have the virus, said Kent Sepkowitz, an infectious disease control specialist at Memorial Sloan Kettering Cancer Center in New York. He also recommends self-quarantines for returnees from the ship.

“She’s likely not a big transmitter if she didn’t transmit the disease to her husband and a third of the boat,” he said of the infected passenger. “The next few days will be key to see if others on the ship develop symptoms.”

No Handshakes

Still, some countries aren’t taking risks. Singapore’s two citizens from the Westerdam have returned and are now in quarantine at a government facility, said Lawrence Wong, minister for national development who co-chairs a task force responding to the virus.

In the Netherlands, RIVM National Institute for Public Health and the Environment, part of the national health ministry, said it plans to test all 91 Dutch citizens returning from the trip, according to a spokesman. If they have no symptoms, they can go home and will be monitored through local health authorities.

The CDC and U.S. Customs and Border Protection didn’t immediately respond to how the U.S. plans to deal with returning Westerdam passengers, as the request was sent Monday on a public holiday.

U.S. officials said on a state department briefing call that roughly 300 U.S. citizens who were on the Westerdam have left Cambodia. Officials said they were tracking those Americans still in Cambodia but had not yet made a decision on whether to send special flights to bring them home.

Hong Kong’s health authorities are in touch with Malaysian counterparts, the WHO and the cruise operator on the details of the case and will conduct contact tracing and medical surveillance if appropriate, according to a department of health spokesperson.

On the Westerdam, the remaining passengers were cheered by news that the tests on fellow travelers have so far come back negative. Still, those on board are taking precautions.

“We are not getting close to any crowds and avoiding coughers,” said V. Padmanabha Rao, an 81-year-old retired surgeon from Virginia who’s traveling with his adult grandson. “Fist bumps instead of handshakes.”

--With assistance from Siraphob Thanthong-Knight, Wout Vergauwen, Peter Flanagan and Shawn Donnan.

To contact the reporters on this story: K. Oanh Ha in Hong Kong at oha3@bloomberg.net;Philip J. Heijmans in Singapore at pheijmans1@bloomberg.net

To contact the editors responsible for this story: Emma O'Brien at eobrien6@bloomberg.net, Frank Connelly, Anthony Palazzo

©2020 Bloomberg L.P.