The mandatory two-week quarantine on the Princess Diamond cruise ship, which ended on Wednesday, was meant to stop the spread of coronavirus. Instead, it might have served as a giant floating incubator.
More than 600 people on board have become infected, and experts warn that hundreds of others getting off the ship could unknowingly be taking the virus with them.
While Japanese health authorities say it’s now safe to end the isolation of thousands of passengers who have so far tested negative, the U.S. Centers for Disease Control says otherwise. The CDC has declared that people leaving the ship cannot enter the U.S. for at least 14 days, as it believes they pose an “ongoing risk.”
“While the quarantine potentially conferred a significant public health benefit in slowing transmission, CDC’s assessment is that it may not have been sufficient to prevent transmission among individuals on the ship,” it said in a statement. “CDC believes the rate of new infections on board, especially among those without symptoms, represents an ongoing risk.”
The Diamond Princess, carrying 3,711 people, went into quarantine off Yokohama on Feb. 5, after a former passenger tested positive for Covid-19.
But even among efforts to stop the spread of the disease on board, the number of infections on board has continued to rise rapidly, swiftly becoming the largest cluster outside Mainland China. On Wednesday, Japan’s health ministry confirmed another 79 infections on the ship, bringing the total to 621 out of 3,011 tested.
READ: The worst coronavirus outbreak outside China is on a ship quarantined in Japan
Efforts at infection control on board have come in for blistering criticism from some medical experts, who fear the quarantine may have effectively acted as an incubator for the disease, with patients becoming infected during the lockdown.
Kentaro Iwata, professor of infectious diseases at Kobe University Hospital, posted a YouTube video Tuesday describing the situation he witnessed on board the Princess Diamond, which he called “completely inadequate in terms of infection control.”
He said that in the chaotic environment on board, the infected were not adequately separated from the healthy, and that he was more fearful for his health on the ship than he had been responding to the Ebola epidemic in Africa.
“I never had fear of getting infection myself for Ebola, SARS or cholera because I know how to protect myself, and how to protect others, and how infection control should be,” he said.
“But inside the Diamond Princess I was so scared.”
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During the quarantine, passengers have largely been confined to their cabins, except for brief sessions when they are allowed on deck for fresh air, provided they wear masks and gloves. But crew members have not been quarantined, and passengers have reportedly been spotted talking to each other without masks across neighboring balconies.
Officials involved in the medical response to the outbreak onboard have also been infected; in the latest case, a doctor who had been on board returned a positive test Wednesday.
As the number of infections rises, Dr. Masahiro Kami, head of the Japanese nonprofit Medical Governance Research Institute, told the Financial Times that he believed that the passengers being allowed to leave could be carriers of the virus, even if they hadn’t yet returned a positive test.
“They could have been infected as they got off,” he said.
READ: Shocking videos show Chinese authorities humiliating people for not wearing masks
Japanese officials have defended their response in the face of the criticism. Shigeru Omi, an infectious disease specialist advising the government, insisted that the “isolation strategy worked,” and said he believed that the majority of infections had occurred before the ship was put in isolation.
But he said that officials had faced major challenges in their work. “Almost 4,000 people stay on this ship, which is not designed for isolation for several weeks, and this is a very challenging situation,” he told reporters.
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For the passengers, who are being released in groups over several days, the end of the quarantine was a huge relief.
“Victory!” tweeted passenger Yardley Wong, a Hong Konger, as he left the ship after 14 days, posting a picture alongside his son flashing the V-sign. “The boys are so ready to have fun again.”
Cover: A passenger who disembarked from the quarantined Diamond Princess cruise ship peeks out of a bus window Wednesday, Feb. 19, 2020, in Yokohama, near Tokyo. Hundreds of passengers began leaving the cruise ship Wednesday after the end of a much-criticized, two-week quarantine that failed to stop the spread of a new virus among passengers and crew. (AP Photo/Jae C. Hong)