Read: A glimpse of the coronavirus’s possible legacy

Hong Kong and Singapore were early examples of places that were able to contain the spread of the virus, which causes the disease COVID-19, offering a model of sorts for countries elsewhere to follow (even if most did not take the cue). Yet now, this city is a different kind of model, a glimpse into what awaits the hundreds of millions of people living under restrictions in places such as Britain, France, Italy, and parts of the United States, wondering what life will look like once the virus is brought under control. The tightening and easing, as well as tweaking, of restrictions under way in Hong Kong, an effort to control the ebb and flow of the disease into manageable waves without letting it run rampant, illustrates how one protracted lockdown is unlikely to be sufficient as researchers take part in a global race to create a vaccine for the virus.

This tactic could keep health facilities from being overburdened, a reality now facing medical workers in New York City and parts of Europe, Gabriel Leung, who is one of the world’s experts on coronavirus epidemics and who worked extensively on the SARS outbreak and led Hong Kong’s response to the 2009 influenza pandemic, told me.

“The suppression-and-lift strategy is the most talked about amongst my ilk and in governments all over the world,” said Leung, who is also the dean of medicine at the University of Hong Kong. “You would need to keep on these control measures to varying degrees until one of two things happen: One, is there is natural immunity by active infection and recovery, or there is sufficiently wide availability of an effective vaccine administered to at least half the population, to create the same effective herd immunity. These are the only two ways of going about it.” Leung added that we’ll go through “several cycles” of tightenings and easings “before we will have resolution.”

Leung’s view is echoed in the scientific community. Research published by the COVID-19 Response Team at Imperial College London this month found that “intermittent social distancing—triggered by trends in disease surveillance—may allow interventions to be relaxed temporarily in relative short time windows, but measures will need to be reintroduced if or when case numbers rebound.” Writing for The Atlantic about how to cope with the virus in the United States, Aaron E. Carroll, a pediatrics professor, and Ashish Jha, a global-health professor, suggested a similar approach. “We can keep schools and businesses open as much as possible, closing them quickly when suppression fails, then opening them back up again once the infected are identified and isolated,” they wrote. “Instead of playing defense, we could play more offense.”

The aim of these measures, such as social distancing, is not to bring the number of people infected down to zero, Leung said; “that is not possible.” Rather, they are an effort to protect older people, who have a much higher risk of becoming infected and dying, as well as to keep health-care systems functioning. “No country, no population, no city can be spared from COVID-19,” said Leung, who is advising the Hong Kong government on its response to the virus. “The big question is, how do you make sure that you do not overwhelm societal functions? How do you make sure that your hospital system does not collapse? How do you make sure that there are enough ICU beds and ventilators for those who need them? How do you make sure that you can minimize the morbidity and mortality burden on your population while protecting the economy and the livelihood of the people on a sustainable basis? These are the big questions that any society would have to grapple with and have been grappling with.”