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 luxury Diamond Princess ship — currently docked at the port city of Yokohama, Japan — were asked to stay on the ship under quarantine orders.

Since then, the number of people aboard with the disease — known as Covid-19 — has surged to 542. While those who tested positive have been allowed to leave the ship for treatment, the rest have had to remain there until at least February 19, with the exception of American citizens.

On Saturday, the US Embassy in Tokyo announced a chartered flight would arrive to evacuate citizens and their families who opted to leave. By the time the group of 328 boarded the plane Sunday, 14 had tested positive for the virus, according to the State Department, but were deemed “fit to fly” since they weren’t showing symptoms.

“These individuals were moved in the most expeditious and safe manner to a specialized containment area on the evacuation aircraft to isolate them in accordance with standard protocols,” the State Department said in a statement. The new cases bring the total number of Americans on the cruise ship who became infected to 58 (of about 400 total).

But they were not the only ones caught in a Covid-19 cruise ship drama. After being barred from docking in five countries, another ship — Holland America’s MS Westerdam — finally disembarked on February 13 in Sihanoukville, Cambodia. Two days later, the ship’s first coronavirus case was confirmed in an American who had already traveled to Malaysia — setting off a global search for other Westerdam passengers who may have been exposed to the virus.

The cruise ship health emergencies have unfolded in the context of a worsening outbreak: As of February 17, there were more than 73,000 cases of the disease and 1,800 deaths, mostly in mainland China.

As a wave of coronavirus panic sweeps the cruise industry, more questions are being raised about how governments and cruise ship operators handled these health scares. Chief among them: Is quarantining people onboard a safe, or even ethical, strategy to contain the virus? Did the measures taken by countries and cruise companies make the outbreak worse? Let’s walk through what we know.

1) What does cruise ship quarantine mean?

Since the 80-year-old passenger tested positive for the virus, the Diamond Princess cruise ship in Japan 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 nearly two weeks 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 rooms, 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 have been 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:

The decision to keep the passengers & crew on the ship is no longer ethical and is wholly inappropriate. 10 crew are infected and crew cannot self quarantine, and room together. Clearly this has transmitted among them placing all at unacceptable risk. https://t.co/8GsI5ThDgg — Michael Mina (@michaelmina_lab) February 11, 2020

Their concern is driven by the mounting case toll and 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 meant 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.

Last Wednesday, a Japanese health official who was checking in on passengers on the ship also tested positive for the virus — raising further questions about whether people on board are protected from 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, Mina said.

3) How are the people on the ship doing?

You can hear from them directly: Passengers and crew have been 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:

Diabetic passenger David Abel says he was without food for 17 hours on quarantined Princess cruise ship after 10 passengers test positive for novel #coronavirus.https://t.co/ih7WAoIJ4h pic.twitter.com/N1Lh5E7zJr — euronews (@euronews) February 5, 2020

"At this moment, we are very scared."



The Indian crew members on the quarantined #DiamondPrincess cruise ship are asking Prime Minister @NarendraModi for help as they remain stranded in Yokohama, Japan #クルーズ船 #CoronavirusOutbreak #coronavirus pic.twitter.com/SFfGdwwvcD — QuickTake by Bloomberg (@QuickTake) February 11, 2020

"We feel like sitting ducks here."



Novelist, Gay Courter explains what life is like being quarantined onboard the Diamond Princess cruise ship, after some passengers tested positive for coronavirus.



Get the latest on #coronavirus here: https://t.co/tNKhlqpEMK pic.twitter.com/ZlvkQimwIF — Sky News (@SkyNews) February 9, 2020

Aun Na Tan and her family have been confined to their cabin on a quarantined cruise ship docked in Japan. Tan says families who booked separate rooms from their children are now unable to see each other https://t.co/yl50Vovw2p pic.twitter.com/KsPvwxHDMi — Reuters (@Reuters) February 10, 2020

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. 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.

It’s also possible the virus could spread through the cruise ship’s ventilation systems, though in a letter to passengers and crew, the US Centers for Disease Control and Prevention said it has no evidence of that yet.

6) So is the cruise ship quarantine an epic failure?

As Fisman and Mina already said, quarantining people on a cruise ship seemed like a bad idea at best and unethical at worst. A Tokyo doctor who specializes in infectious diseases told the New York Times that the experiment was “an unprecedented failure.” We should learn from this lesson that a quarantine on a ship is impossible, and we should not repeat this in the future,” Eiji Kusumi said.

But others point out that the cruise ship company and the Japanese government were caught in a difficult position. “In a perfect world,” Bogoch said, “the passengers could have been let off the ship” then placed in a safe quarantine environment in Japan or sent back to their home countries for medical care there. “But the logistics of letting 3,700 people off a ship and finding appropriate accommodations, medical care, and basic needs — with no warning — would be challenging at best,” he added.

At the same time, the global community has had ample warning for years that a pandemic threat of this nature could arise at any time. So one can make the argument that governments, even cruise companies, should have been ready with an emergency plan in place.

7) What happened to the Americans who evacuated the ship in Japan, and the passengers who left the Westerdam ship in Cambodia?

On Sunday, 328 Americans got on two cargo planes headed for military bases in the US: the Travis Air Force Base in Fairfield, California, or Lackland Air Force Base near San Antonio, Texas. But after the passengers had already left the ship, the US government got the results of their recent coronavirus tests and learned that 14 tested positive for the virus.

The State Department decided to repatriate them anyway, simply separating them from other passengers on the planes in an area cordoned off using plastic sheets, according to the Times.

Separately, the Westerdam passengers were welcomed in Cambodia on February 13, and then dispersed around the world — returning home or onward with their travels. At the time, no one had tested positive for Covid-19. But two days later, the ship’s first coronavirus case was confirmed in an American passenger who had already traveled to Malaysia, raising questions about the ship’s and Cambodia’s thoroughness in testing passengers. Her case has set off an unprecedented global search for other Westerdam passengers who may have been exposed to the virus.

8) What do these cruise ship emergencies reveal about the larger outbreak?

The Japanese case shows us that quarantining people on a cruise ship to stop the spread of Covid-19 can backfire, while the Cambodia case suggests that letting people disembark and disperse around the world can create a public health nightmare. In both cases, there appears to have been sloppiness: Proper quarantine protocols weren’t followed, and passengers weren’t adequately tested before moving on with their travels.

While all parties involved could have done better, the situations also reveal just how challenging containing the spread of this highly contagious virus is going to be in a time of global travel.

On the bright side, the cruise ship debacles could actually contribute to science. “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 understanding precisely what impact the quarantine had on the larger outbreak: 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.

9) 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.

Cruise ships and viruses: studied them for years with norovirus https://t.co/ppx4EsVG0J check out this paper: we found that cruise ship outbreaks were an early warning indicator of new pandemic norovirus variants https://t.co/hT6sMcoVFO — Marion Koopmans (@MarionKoopmans) February 6, 2020

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.