On Feb. 1, a man in Hong Kong was diagnosed with COVID-19, the new coronavirus. A few days earlier, he had disembarked a cruise ship whose name would soon be known around the world: the Diamond Princess. A mandatory quarantine placed on the ship by the Japanese Ministry of Health ended on Wednesday, even as dozens more cases have been diagnosed, bringing the total of sick cruise passengers to around 450. Clearly, the crisis is not exactly in hand, leaving everyone with one simple question: Do quarantines like this one even work?

Clearly, the crisis is not exactly in hand, leaving everyone with one simple question: Do quarantines like this one even work?

This isn’t a new question for America, or even the world, to grapple with. In 2013-16, West Africa experienced the worst outbreak of the ebolavirus disease to date, and multiple kinds of quarantine were implemented, both within the affected countries of Sierra Leone, Liberia and Guinea and in other countries. Within the U.S., a public health nurse, Kaci Hickox, was placed in a tent connected to a hospital, with a port-a-potty and a telephone, and told to sit and stay for 21 days, solely based on the fact that she had come back from a Doctors Without Borders assignment in Sierra Leone. While Hickox didn’t have a fever on an initial test, after several hours in a warm interrogation room, she had a flushed face that registered a temperature on a forehead scanner.

Hickox successfully fought her quarantine, arguing — correctly — that the ebolavirus is not contagious before symptoms, and it would be perfectly safe for her to remain in her community and self-monitor her symptoms for the known incubation period while checking in with a public health officer.

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The basis of this argument comes from the idea that quarantine is a coercive measure that infringes upon people’s rights. If you are going to use it, you better have a really good reason for it. Specifically, you need to show that it’s a proportional response to the severity of the disease — not just how contagious it is, but also how harmful it is. You have to show that it’s necessary, that a community monitoring system like they’re using in the U.K., where health care workers advise, monitor and even test possibly sick residents over the phone, can’t work, and that self-reporting of symptoms also wouldn’t work. The public has to understand what’s going on, and why, and it should be clear that quarantine is the option that infringes the least on everyone. And perhaps most important, it’s got to be effective in stopping the spread of disease.

Cruise ships, it turns out, are not good places for quarantines — surprising nearly no one with a public health background. Cruise ships are a confined space, and we know from past outbreaks that viruses really like to run rampant in confined spaces. This is most classically seen on cruise ships with norovirus, but there have also been outbreaks of measles, E.coli, influenza, and chickenpox; a U.S. submarine, another confined space, recently had an outbreak of mumps. There’s a reason, after all, why some public health specialists refer to cruise ships as floating petri dishes.

But it also turns out that cruise ships aren’t a good place for quarantine because quarantine itself is a problematic concept, rooted in an ancient understanding of how disease spreads. The name itself comes from 14th-century Venice, where political and public health policy required ships from possibly plague-ridden countries to remain isolated for 40 days, giving any incubating diseases a chance to run their course. The number 40 itself was selected partly for its religious connections, and partly because the dominant medical system of the day said that disease was spread via miasma, or poisonous vapors, and it took 40 days to isolate, fumigate, disinfect and purify the “bad air.”

The idea of quarantining cities isn’t new, either — historically called cordon sanitaires, they used city walls or soldiers to separate the possibly sick from the well. You could opt to close the gates and keep out stick people … or keep them in. Or more precisely, keep their foul air contained. The most famous of these was most likely the 18th-century Austro-Hungarian Pestkordon, which stretched nearly 1,200 miles in an effort to stop plague from repeatedly invading Europe. Of course, like most of these efforts, the actual disease it was preventing had circulated out of the population nearly 15 years before the wall was complete.

More recently, during the 2003 SARS-CoV-1 epidemic, Hong Kong enacted quarantine protocols first designed to handle plague in the 1890s. In one well-known incident, when police officers arrived at an apartment complex to order everyone inside to remain quarantined for 10 days, they found nearly half of the 264 apartments empty: People had read the news, heard what was coming and left rather than be contained. It is estimated that in Toronto, which also experienced a large quarantine in an effort to stop SARS, 43 percent of people violated the quarantine.

In the Ebola outbreak in 2014, Doctors Without Borders said it was their experience in Liberia and Sierra Leone "that lockdowns and quarantines do not help control Ebola, as they end up driving people underground and jeopardizing the trust between people and health providers.”

In the process, quarantines can cost governments huge sums and possibly help the spread of disease by pushing panicking citizens out of their daily routine, homes or even cities.

So while history tells us quarantines have been around for over 600 years, history also tells us they’ve never been particularly effective, either because of an incorrect theory of how disease works, an incorrect understanding of human behavior, or because every way station and city seemed to have its own rules for when to quarantine a person or cargo. It’s kind of like we are seeing now with the Diamond Princess passengers. In the process, quarantines can cost governments huge sums and possibly help the spread of disease by pushing panicking citizens out of their daily routine, homes or even cities. Or in the case of cruise ships, quarantines set up an ideal laboratory to spread disease between individuals.

None of this is to say that countries have no options in the face of an outbreak. Authorities can enact basic social distancing measures, like limiting the ability of large groups to get together, whether it’s for a concert or the Lunar New Year, or even closing down big office buildings. Other options include reminding people to engage in cold prevention measures, like washing your hands frequently (and correctly), avoiding touching your face and eyes, coughing or sneezing into your elbow, and not shaking hands. Finally, authorities can encourage people who feel sick to stay home and monitor their symptoms, contacting a doctor if they have any concerning symptoms.

No one would argue that medicine today is the same as medicine in the 14th century, and very few people are looking for 14th century treatments in the 21st century. We owe it to everyone to treat potentially exposed/ill patients in a 21st century manner, as well. Especially when the data tells us two things: Quarantine is an out-of-date concept to treat disease, and a cruise ship is the last place you want to hold an impromptu one.

CORRECTION (Feb. 23, 12:50 p.m. ET): An earlier version of this article misidentified the cruise ship recently quarantined by the Japanese Ministry of Health. It is the Diamond Princess, not the Diamond Prince.