HONG KONG • More than 3,000 travellers on two coronavirus-stricken Carnival Corp cruise ships are returning home, fanning out to more than 40 countries and fuelling fears of further contagion from the deadly virus.
The United States yesterday began evacuating its citizens from the Diamond Princess off Yokohama, Japan, where local media reported that another 99 people have tested positive for the virus, bringing the total number of confirmed cases on the ship to 454.
The Health Ministry declined to confirm the reports immediately. It was also not clear whether the figures included 14 US citizens who tested positive for the virus but were allowed to board evacuation flights home.
Canada and other countries are also planning similar evacuations of hundreds. Hong Kong is set to do so as well.
Last Saturday, an 83-year-old American woman tested positive in Malaysia, a day after she and more than 2,200 others were cleared to leave the MS Westerdam cruise ship in Cambodia.
The ship arrived there after being turned away by five other ports.
"This woman was on the boat and was infected for a few days - she could have potentially exposed other people on the boat who have now gone home," said Stanford University professor Stanley Deresinski, who is an infectious disease specialist at the university hospital.
"There is a possibility that anyone who is infected and asymptomatic could start a chain of infection wherever they return to," he added.
The startling number of cases on the Diamond Princess, which accounts for the biggest cluster of coronavirus infections outside of China, and the newly detected case from the Westerdam raise questions about the effectiveness of containing the virus on cruise ships.
Those concerns have prompted a growing number of Asian countries to block the luxury liners from their ports, threatening earnings of companies such as Carnival and Royal Caribbean Cruises.
"Cruise ships are very high risk for transmission of illnesses," said transport geography professor Jean-Paul Rodrigue of Hofstra University in New York. "People are circulating all over, you are using the same corridors, touching the same handles and railings. It is easy to catch something."
The Westerdam spent two weeks in limbo before Cambodia permitted the ship to berth last Thursday.
Passengers were allowed to leave the next day without a quarantine, and the American woman then travelled to Kuala Lumpur to seek a flight back to the US.
All but the American woman and her husband, who tested negative, were eventually allowed to continue to their destinations, including airports in the US, the Netherlands and Australia.
Malaysia has since said it will not allow any more travellers from the Westerdam to transit through the country, causing the cancellation of three charter flights to shuttle passengers out of Cambodia.
Health experts are raising the alarm about the Westerdam passengers after their release without a quarantine order at a time when the death toll from the disease has topped 1,700 globally.
Most countries planning evacuations of those on the Diamond Princess in Japan have also announced plans for quarantines.
Westerdam passengers should at minimum be monitored by the local health authorities and quarantine themselves, said Prof Deresinski and other health experts.
The authorities could also consider testing returning travellers from the ship if feasible, he added. "It doesn't require prolonged exposure to be infected."
The incubation guideline for the coronavirus is two weeks - nearly the entire time the ship was at sea after departing Hong Kong on Feb 1 and becoming a floating pariah.
As the ship was at sea for the required 14-day quarantine, passengers are free to travel after they leave the ship, a US State Department spokesman said. Holland America Line - owned by Miami-based cruising giant Carnival - has maintained there was no known case of the disease during the voyage.
Knowing when the American woman was infected and by whom is key to determining the risk of other passengers coming down with the virus.
"I don't know enough about this patient to know if it is possible she was infected prior to boarding and had a long incubation period," said Professor Ben Cowling, a professor of epidemiology at Hong Kong University.
"Perhaps it is more likely that they were infected on board, which suggests that there was at least one other case on board, that is, the person who infected them."
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