The pair consider how quarantine – derived from the Italian quarantina for the 40-day period once believed to be the turning point for disease – developed into a ubiquitous practice to halt contagion not only among humans. They show how it has been used to keep plants and animals safe (although incineration and extermination are often the solution); keep space exploration free of contamination; and keep nuclear waste in “a strange kind of purgatory”.

The book, which brings life to a deadly serious subject, also looks ahead and cautions about new normals: “The temporary infrastructure and controls on mobility put in place during a pandemic often harden into permanent borders, bureaucracy, and, too often, inequities,” they write. An example that hails from the plague era in Italy is the passport, now a fixture.

Although a timely subject these days, before Covid-19 placed half of humanity under medical detention, quarantine appeared increasingly outdated. “Our insistence that [it] still had modern relevance was occasionally met with disbelief,” the authors write.

Even public health officials questioned its future importance, largely because medical countermeasures – vaccinations, drugs – had seemingly rendered the practice obsolete. Then there were the associated ethical, economic and other risks, surveillance and monitoring adding to them.

How 21-day quarantine damages mental health, with long-lasting effects

Speaking from their home in Los Angeles, Twilley and Manaugh recount research trips to, among other places, the Italian city of canals, Venice, and Dubrovnik, Croatia, which in 1377 was the site of the world’s first state-imposed quarantine. During the Black Death, which killed 20 million people, almost one-third of Europe’s population, those cities confined to special hospitals called lazarettos the infected and anyone else suspected of harbouring the flea-borne disease.

That the facilities were built even before germ theory was understood makes sense. Sequestration seemed sensible because of the uncanny link between disease and ships transporting people and goods from foreign lands. The conflation with xenophobia continues today.

As primitive or crude as it might appear in the 21st century, quarantine still provides a vital buffer between the known and unknown – although strictly speaking, the authors point out, confirmed cases enter isolation, whereas quarantine is a period of waiting “to see if something hidden within you will be revealed”.

Interesting, however, is quarantine’s move from the periphery. Where lazarettos tended to be isolated, on islands and peninsulas, medical confinement has entered cities and our homes (listen to our podcast to hear how Google’s Alexa may soon determine whether to let you out of yours).

“The first new federal quarantine facility built in more than a century in the US is smack in the middle of the country,” Twilley says, referring to the National Quarantine Unit in Omaha, Nebraska, which began operation in January 2020. And these days, separation, once provided through physical geography (think also cordons sanitaire), is achieved with technology.

Indeed, quarantine’s future is a question of technology, they believe. But going forward relies also on a collective rather than an individual response, and mutual trust. China’s fangcang could be part of the solution.

Ironically perhaps, given media coverage last year of Chinese forcibly detained on suspicion of Covid-19 infection in Wuhan, social activities were among doctors’ orders in those enormous makeshift shelter hospitals set up in stadiums and the like to accommodate thousands of people testing positive but exhibiting only mild or no symptoms. Human connection, addressing emotional and social needs, recalls communal Venetian experiences in centuries past, says Manaugh.

Then as now, suffering shared was suffering less­ened, leading to recognition of mass responsibility and of the whole being greater than the sum of its parts.

“It seems that people in China had actually thought through what you might need to get through this period of enforced separation from the world,” says Twilley, returning to the idea of civic duty.

Public health is meaningless, she reiterates, unless we think of ourselves as a public.

From Edgar Allan Poe to Stephen King, writings about quarantine and disease

Geoff Manaugh and Nicola Twilley, authors of Until Proven Safe: the History and Future of Quarantine, appear this week on The Post Books Podcast, a South China Morning Post production on SoundCloud (sc.mp/3590c3), hosted by Charmaine Chan.

Quarantine lends itself to innumerable metaphors and has been employed widely in myths and literature. For example, the underworld surfaces in connection with the nuclear-waste industry, which the authors investigated in their analysis of management of radioactive contaminants. Their book also probes quarantine’s role in bolstering food security – crucial if, indeed, the world is one pathogen away from starvation.

Among the many novels and short stories that infected their imagination during research was The Death of Grass, a 1956 novel by Sam Youd (pen name John Christopher) about a virus that kills all grass, including rice and wheat.

King’s book, says Manaugh, is about “containment gone awry”. It eerily tells of a pandemic caused by the escape from a research laboratory of a deadly strain of influenza.