The coronavirus cruise ship quarantine is a scary public health experiment

The Diamond Princess cruise ship sails out of Japan’s Yokohama Port to undergo procedures at sea before returning to Daikoku Pier, where it will continue to be resupplied and screened for new coronavirus cases. | Carl Court/Getty Images

The second-largest outbreak outside China is floating at sea — and health experts are increasingly worried.

It’s a hypochondriac’s worst nightmare and a startling public health crisis: The largest coronavirus outbreak outside of mainland China is currently floating in Japanese waters, on a cruise ship owned by Princess Cruises.

The outbreak was first detected when an 80-year-old passenger tested positive for the virus on February 1, a week after disembarking in Hong Kong. By February 4, the remaining 3,700 passengers and crew of the Diamond Princess — currently docked at the port city of Yokohama, Japan — were asked to stay on the ship under quarantine orders.

Since then, the number of passengers and crew aboard the Diamond Princess with the disease — known as COVID-19 — has surged to 218. While those who’ve tested positive are allowed to leave the ship for treatment, the rest have to remain there until at least February 19 with the exception of Americans on board. On Saturday, the US Embassy in Tokyo announced a chartered flight would arrive to evacuate citizens by Sunday.

“We recognize this has been a stressful experience and we remain dedicated to providing all the support we can and seeing you safely and expeditiously reunited with family and friends in the United States,” the letter said, according to the New York Times.

They’re not the only ones who have been stuck aboard a cruise ship in Asia because of Covid-19, as the disease is known. After being barred from docking in five countries, Holland America’s cruise ship MS Westerdam finally disembarked on February 14 in Sihanoukville, Cambodia. The ship had no confirmed coronavirus cases.

The cruise ship drama is unfolding in the context of the worsening outbreak: As of February 15, there were more than 67,000 cases of the disease and 1,400 deaths, mostly in mainland China.

As a wave of coronavirus panic sweeps the cruise industry, more questions are being raised about whether quarantining people onboard is a safe, or even ethical, strategy to contain the virus. Chief among them: Is it doing more harm than good? Let’s walk through what we know.

1) What does cruise ship quarantine mean?

Diamond Princess Cruise Ship Remains Quarantined As Coronavirus Cases GrowCarl Court/Getty Images
Emergency workers in protective clothing walk from the Diamond Princess cruise ship as it sits docked at Daikoku Pier.

Since the 80-year-old passenger tested positive for the virus, the Diamond Princess cruise ship has transformed into a mass public health experiment. Passengers who have tested positive for the virus have disembarked and been admitted to hospitals in the Yokohama area, according to the World Health Organization. The others have been held in quarantine onboard at the order of the Japanese Ministry of Health.

For over a week now, the passengers on the ship have been asked to stay in their rooms, wear masks, and only walk on the deck for a couple of minutes each day, keeping at least six feet of distance from other passengers. They’re having meals delivered to their room, and have plenty of TV, movie, and newspaper options to keep them busy.

Officially, the objective of this quarantine is to prevent further spread of the virus onshore, particularly ahead of the Summer Olympics, which begin in Tokyo in July.

“In this unprecedented situation, the Japanese Ministry of Health authorities are working with us collaboratively on additional enhancements and approving new procedures as we adapt our process to the unique challenges of this situation,” said Jan Swartz, president of Princess Cruises, in a statement.

On the other hand, “The Japanese government is probably valuing stopping the spread of the novel coronavirus to their country more than the higher risk of harm to passengers from this mass cruise ship quarantine,” said Steven Hoffman, director of the Global Strategy Lab and a professor of global health at York University.

The quarantine is supposed to end on February 19, according to Princess Cruises, “unless there are any other unforeseen developments.” So it’s not yet clear whether it will end then. And that’s a source of worry for reasons we’ll get to next.

2) Could the quarantine lead to more coronavirus infections?

Doctors and health researchers are increasingly skeptical of this quarantine for exactly that reason. “They’ve basically trapped a bunch of people in a large container with [the] virus,” said University of Toronto epidemiology professor David Fisman, over email. “So [I’m] assuming ‘quarantine’ is generating active transmission.”

For the same reason, Michael Mina, another epidemiologist at Harvard University, called the quarantine unethical on Twitter:

Their concern is driven by the details emerging from the ship, which paint an alarming portrait. According to a must-read New York Times report, as of February 10, Japanese officials had only tested 439 of the 3,700 passengers onboard for the coronavirus, citing shortages of testing supplies. This means that at least a fraction of the remaining thousands onboard may have the virus and not know it.

Among those who’ve tested positive recently are 10 crew members. “And according to employees, the infected crew members identified on Sunday had been eating in the mess hall alongside their co-workers,” the Times reports.

On Wednesday, a Japanese health official who was checking in on passengers on the ship also tested positive for the virus.

Given the risk of further spread among the crew, and to the passengers they’re trying to serve, the quarantine on the Diamond Princess increasingly seems to pose an “unacceptable risk,” as Mina said.

3) How are the people on the ship doing?

You can hear from them directly: Passengers and crew are sharing their experiences of the quarantine through tweets and videos. And they’re reporting more fear and anxiety every day as more people are diagnosed:

4) How can the cruise company just lock these people up?

It’s not the cruise company quarantining people; it’s the Japanese government.

People on the ship “are in Japanese waters, and this is being managed by public health officials in Japan,” said Isaac Bogoch, a professor at the University of Toronto. So the passengers onboard the ship, as visitors of Japan, are subject to Japan’s quarantine protocols, he added. According to the cruise company, the passengers hail from all over the world: America, Australia, Canada, and Japan, among other countries.

5) Is this quarantine ethical?

Quarantines can be effective tools for containing the spread of disease — but only when you’re dealing with people who are already sick. “All the evidence we’ve got to go on is based on quarantining people who are infected,” said Mark Eccleston-Turner, a global health law researcher at Keele University in England. When quarantines are done arbitrarily, with no scientific basis, he added, they’re “not in line with human rights obligations.”

The cruise ship quarantine is not just a human rights or justice issue, though; it’s a public health problem, too. In this case, people who aren’t yet sick and who may not have been exposed to the new coronavirus are being held together in close proximity with people who may already have the disease. Layer on top of that the fact that we don’t yet know exactly how this virus spreads; all we know is that respiratory viruses like it — MERS and SARS — spread mainly through exposure to droplets, from coughing or sneezing.

But like SARS, there’s already some suggestion that the new coronavirus may be able to spread long distances through pipes in buildings, and potentially via feces, too.

6) What does this cruise ship situation reveal about the larger outbreak?

Though the cruise ship situation is unfortunate, it could be helpful for understanding the new coronavirus. “It may shed light on the incubation period [for this disease], transmission dynamics, the clinical spectrum of illness,” said Bogoch.

Marion Koopmans, who studies emerging infectious diseases and heads the department of virology at Erasmus Medical Center in Rotterdam, Netherlands, thinks we can learn a lot about how the disease spreads when we know exactly how the virus began spreading on the ship. “Cruise ships have these shows, several restaurants with joint dinners — so was there a close contact situation that involved a sick person with many people around him or her?” she wondered.

There’s also the question of how the quarantine worked: whether the passengers and crew would have acquired the new coronavirus with or without being forced to stay on the ship. “Are these truly new infections acquired after quarantine, or would these people have already acquired [the virus] and it’s just the regular incubation period?” Bogoch asked. Once we get answers to these questions, they might shed light on the larger outbreak.

7) Given the potential for outbreaks like this, should cruises be banned?

There is indeed a surprisingly robust science of disease spread on cruise ships — in particular, from norovirus, the highly contagious bug spread by ingesting the stool or vomit of an infected person, often through food or touching a contaminated surface.

Koopmans said she wasn’t sure if that’s because of “surveillance bias” — we’re more likely to hear about what happens on a massive cruise ship than in a small hotel or restaurant — or because there’s something inherently risky about cruise ships.

She has studied norovirus outbreaks on cruises extensively and came to a striking finding in one paper: The researchers looked at norovirus outbreaks over time and found that whenever a new, fast-spreading variant was emerging, it was often accompanied by a big wave of outbreaks on cruise ships. In other words, what happened aboard was a signal that there was a larger outbreak on the ground. “For a virus that likes to spread in groups of people, cruise ships are notorious,” Koopmans added.

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