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With countries from Italy to the U.S. having waited too long to combat the coronavirus, many experts in public health and epidemiology are pleading with government officials not to compound the mistake by lifting stay-at-home and other social distancing measures too soon — and, in fact, to impose strict ones in U.S. states and cities that haven’t.

But from the World Health Organization to New York Gov. Andrew Cuomo to epidemiology modelers across the globe, there is growing recognition that the time will and must come to tiptoe back toward normalcy.


That recognition is driving the next life-and-death questions in the coronavirus pandemic: What is the exit strategy? How will we know when it’s safe to implement it? If this first wave of outbreak eventually crests and dissipates, as it has in China, what’s the plan if the virus returns with a vengeance in a few months? Can that plan be less disruptive to livelihoods and ordinary existence than the panicked responses in many western countries over the last month, and more like the surgical strikes that seem to have succeeded in Singapore and South Korea?

The “when can we?” research, unfortunately, is playing out against a highly politicized background. President Trump on Tuesday vowed to return the country to “normal” by Easter, April 12. But while the epidemic in the U.S. is still far from under control, much less peaking, apolitical experts are nevertheless cautiously starting to figure out how smarter, targeted approaches could serve as an off-ramp for the current control measures and how to do better next time, especially if Covid-19 cases rebound after the current outbreak fades.

“You can’t stop the economy forever,” Cuomo whose state has more Covid-19 cases and stricter restrictions than any other said in a news conference on Monday. “So we have to start to think about, does everyone stay out of work? Should young people go back to work sooner? Can we test for those who had the virus, resolved, and are now immune and can they start to go back to work?”


He and others who cringe at the very thought of relaxing social distancing, including many infectious disease experts, are asking how to do it right, or at least better. There is reason to hope that will be possible. An emerging consensus points to aggressive tracing of contacts of sick people, much broader testing, targeted quarantines, and new online tracking technology as strategies that would facilitate the easing of social distancing measures.

Scientists including infectious disease epidemiologist Marc Lipsitch of the Harvard T.H. Chan School of Public Health, one of the most forceful voices against easing up prematurely on containment and mitigation, conclude in a new paper that in a best-case scenario, “summertime social distancing can be less frequent.” After that, they explain in an analysis published as a preprint on Tuesday, their mathematical model of how people interact and how infections spread suggests that, if the epidemic returns, “aggressive contact tracing and quarantine – impractical now in many places but more practical once case numbers have been reduced and testing scaled up – could alleviate the need for stringent social distancing to maintain control of the epidemic.”

Authoritative support for the possibility of an exit strategy and more targeted countermeasures against a second wave came on Wednesday. Researchers at Imperial College London, whose earlier model projected apocalyptic levels of Covid-19 deaths across the U.S. and United Kingdom absent near-China-level lockdowns and other forms of social distancing, concluded that in once-frozen cities such as Wuhan, “intermediate levels of local activity can be maintained while avoiding a large outbreak.”

The new data, they wrote, “suggest that after very intense social distancing which resulted in containment, China has successfully exited their stringent social distancing policy.” There are indeed “exiting strategies,” Neil Ferguson and his colleagues conclude, and they “can inform decision making processes for countries once containment is achieved.”

The optimism depends on first controlling the current outbreak, however. In many places, that isn’t even in sight, as many hospitals careen toward collapse and U.S. cases and deaths soar. In a TED video chat on Tuesday, Bill Gates warned that re-opening commerce too soon would be tantamount to “ignor[ing] that pile of bodies over in the corner.”

The point of lockdown measures, WHO Director-General Tedros Adhanom Ghebreyesus said during a briefing Wednesday, “is to enable the more precise and targeted measures that are needed to stop transmission and save lives.”

If today’s stringent measures remain, and people adhere to them better than they have, the curve will not only “flatten” but peter out. In that case, key decisions going forward will focus on how to keep Covid-19 cases to a manageable level during a second outbreak.

Singapore subway
Commuters wear face masks on the subway in Singapore on March 18. CATHERINE LAI/AFP via Getty Images

The approach getting the most support is one that experts have long doubted could work with a respiratory virus: aggressive case finding, contact tracing, community surveillance, isolation of cases, and quarantining of contacts. Both Singapore and South Korea used that, allowing them to make tactical decisions about schools (mostly open in both countries) and public movement, sparing them from shutting down to the extent that the U.S. and many countries in Europe have.

That suggests an exit strategy for the U.S. “If the case numbers are really low enough, you can do a more Singapore-like or Iceland-like strategy of following individual cases rather than just social distancing,” Lipsitch told reporters on Tuesday. (It’s not clear what “low enough” means, though it would be based in part on hospital capacity.) If public health agencies conduct intense testing, including of people without symptoms, and identify and test their contacts, he said, “you may be able to get away potentially with less social distancing the second time around, because you’re also controlling the individual cases.”

The value of doing so would be enormous, since it could replace the draconian steps that are the only option when chains of viral spread can’t be tracked but that have been financially ruinous, especially to low-wage workers. Although “the feasibility of [widespread testing and contact tracing in the U.S.] remains to be seen and requires a lot of coordination that doesn’t yet exist,” Lipsitch cautioned, there are at least two reasons to think it could be brought into existence: technology and weather.

Earlier this month Health and Human Services Secretary Alex Azar called contact tracing “the basic blocking and tackling” to contain an epidemic. Infectious disease experts have never thought contact tracing could work for respiratory diseases (it isn’t done for flu): It takes so long and these infections move so fast. But in 2020, there’s an app for that.

One called Private Kit: Safe Paths, developed by scientists at the Massachusetts Institute of Technology, would upload data to a privacy-protected site on cases and where they had been. Users who had been in close contact with that person would get a notification and could then isolate themselves for two weeks, slowing viral spread from people without symptoms. In contrast, simply interviewing a single case and identifying that person’s contacts takes an average of 12 hours, said MIT’s Francesco Benedetti. Worse, people can’t remember exactly where they were, let alone what strangers they brushed against or breathed on, two weeks ago.

But the near-instantaneous contact tracing made possible by technology “is one of the most important steps we can take, the infectious disease specialists we worked with tell us,” Benedetti said. “This addresses the need for speed.” The technology should be ready for nationwide use “soon,” he said.

It mimics what Singapore was able to accomplish: banning mass gatherings, yes, but not closing schools, and — crucially — interviewing patients and using security camera footage to identify those they encountered and order them into home quarantine. That severed numerous transmission chains.

In Israel, researchers are testing a similar tool to identify and predict virus hot zones. A smartphone-based questionnaire asks people their age, gender, and location as well as whether they have such Covid-19 symptoms as cough, fatigue, shortness of breath, and diarrhea. Some 320,000 Israelis have filled it out, revealing a significant increase in reported symptoms in places where known patients passed through, said Eran Segal of the Weizmann Institute of Science — an indication that the survey can augment laborious contact tracing by health workers. Israel’s case count reached 2,170 cases on Wednesday.

The tool lets a country (or state or city) “identify, ahead of time, regions of outbreak of the virus,” Segal said. “This will allow health officials to deploy testing in a smarter way, identify those individuals who are infected, and isolate them. It can also allow tightening the lockdown in specific locations but more importantly, relieving the lockdown in other regions where no outbreak is expected.”

That suggests not only an exit strategy but also a next-time strategy, he said. “When we eventually release the population from lockdown, such a tool can be critical in management of the spread of the virus, as it may ahead of time inform us of regions where the outbreak is re-emerging.”

It will take weeks, and maybe months, to refine and deploy tools like these. But we may have that breathing room.

How summertime temperatures will affect the virus remains unknown. But there are reasons for optimism.

Although the research is far from definitive, several studies in China find that higher temperatures do decrease Covid-19 incidence. One, a modeling study posted to the preprint site medRxiv on Tuesday, “confirmed that transmission rate decreased with the increase of temperature, leading to further decrease of infection rate and outbreak scale,” scientists at China Medical University wrote. One reason may be that this coronavirus, like that which caused the SARS epidemic in the early 2000s, can’t survive on surfaces as long in warmer weather.

The new coronavirus emerged during flu season, making people wonder — will cases start going down as spring rolls around, just like the flu? Hyacinth Empinado and Alex Hogan/STAT

“Other coronaviruses are seasonal,” said Jeff Shaman of the Mailman School of Public Health at Columbia University. “So we might catch a break here.”

The decision by the U.S. and other countries to close businesses, cancel events, issue stay-at-home orders, and ban large (and now small) gatherings was partly driven by the early mathematical model created by the Imperial College team. That drove policies that prioritize widespread and strict countermeasures rather than more targeted ones.

Now that more experts have dug into the model, they are questioning whether officials drew the right conclusions and, especially, whether economy-crippling policies can be avoided once the first phase of the outbreak passes.

For instance, the Imperial College model does not allow for the possibility of detecting asymptomatic individuals through mass testing or contact tracing, as South Korean did instead of issuing stay-at-home orders. With such mass testing, infected people can be identified even before symptoms appear and can isolate themselves for two weeks.

The critics’ intent is not to slam the highly respected Imperial College team, but to suggest that different assumptions can illuminate the exit strategy and the “next time” strategy.

“The model does not account for important individual-level behavior changes that many people adopt to protect themselves in epidemics,” said epidemiologist and modeler Gerardo Chowell of Georgia State University, including “increased hand washing, staying home if sick, reducing social activities, and wearing a face mask.” He agrees that simple face masks do not keep the virus out very well, but they help keep it in, especially when infected people cough or sneeze or even speak. Widespread use of face masks, as in Japan and other countries in east Asia, would be less disruptive than lockdowns.

Another exit strategy, he and others argue, is targeted intervention. “Factors such as population density, urbanization, environmental factors including temperature and humidity, and connectivity to the rest of the world have been shown to drive transmission rates,” Chowell said. “The intensity of the social distancing interventions have to be implemented in light of the local infectious dynamics,” as does the timing of any easing of restrictions.

The question of timing is, of course, key. “The conservative approach is to wait till there are no new cases in an incubation period,” said Yaneer Bar-Yam of the New England Complex Systems Institute, who uses the science of complex interactions to create mathematical models of epidemics. But once the peak of an outbreak has passed in any region, and if travel restrictions prevent imported cases, “we have every reason to believe [contact tracing and isolation of cases and contacts] can work.”

He, too, sees hope for a more targeted approach soon. “Travel restrictions prevent spreading the disease from areas that have it to those that don’t,” Bar-Yam said, “and enables relaxing restrictions earlier in areas where it has been eradicated. Testing enables rapid isolation of individuals so we don’t have to isolate as many people in order to stop the outbreak.”

More and more modelers are discussing “precision quarantine,” as Momiao Xiong of the University of Texas Health Science Center and colleagues in Shanghai call it, to “slow down and keep people from transmitting the disease.” That could help with both an exit strategy and a next-wave strategy.

“Even in a semi-locked-down state, you can prioritize [for testing and contact tracing] people in grocery stores, banks, delivery, and others who come into contact with a lot of people and are therefore most at risk of being super-spreaders,” said Columbia’s Shaman. They should be tested repeatedly.

At the beginning of the outbreak it was unclear if super-spreading occurred, as it did with SARS in 2003, but researchers in China have found that it does: One Covid-19 patient infected 52 others, they reported on Monday.

“The main thing we want to do [during any summertime respite from the outbreak] is get ourselves ready to do extensive testing,” Shaman said. “If it’s sensitive and specific enough, it would allow us to track and isolate people who are infected and their close contacts.”

If people do not carry the virus, there is no reason they couldn’t gather in large groups, he said. To make that as safe as possible, potential super-spreaders — those who come into close contact with hundreds of people — should be tested and tested again, both now and going forward.

Testing shouldn’t wait until cases start mushrooming again, as China’s experience shows. Without the lockdowns and other measures in Hubei province, scientists there estimate, the number of Covid-19 cases would have been 67-fold higher. Early case detection and isolation prevented more infections than travel restrictions, they conclude, but speed is key: If countermeasures had kicked in three weeks earlier, China would have had 95% fewer cases.

An analysis of how China, Hong Kong, South Korea, and Singapore controlled the coronavirus outbreak also concluded that the strategy with the greatest impact was rapid testing, contact tracing, and quarantining cases and those they might have infected, for two weeks. That was more effective than travel bans, lockdowns, and school closings, Andrew Tatem of England’s University of Southampton and his colleagues found.

If policymakers needed any more reasons to prepare for extensive testing and the targeted countermeasures that would allow, it’s this: Covid-19 could well return next fall with a vengeance because of today’s social distancing measures.

There will be “a high proportion of susceptible individuals in the population,” Harvard’s Lipsitch and his colleagues explained in their analysis. That could lead “to an intense epidemic … in the late autumn and winter.”

Even  then, the world will likely not see the end of this coronavirus. Instead, they conclude, it will “circulate seasonally with winter peaks in subsequent years.”

Andrew Joseph contributed reporting.

  • Regarding your quote of Dr. Gerardo Chowell on face masks, I would like to add:

    Face masks help more than people think – the black-and-white message of the CDC (“stop buying them … they are ineffective”) and many experts is not helpful. If our goal is to flatten the curve, not eradicate the virus, then any partial protection by a physical barrier will help as mathematical models can show.

    Moreover, the latest single-cell RNAseq measurements reveal that ACE2 receptors that the Cov-2 virus uses as entry is predominantly expressed in the nasal mucosa, and much less in the lower lung. The nose is where big cough-expelled droplets land: those that (unlike the microscopic aerosol droplets) can be readily blocked by any physical barrier, such as those so imperfect surgical masks – or your scarf.
    For more see:

  • The US now has the highest number of cases of any country in the world. There is not enough material to keep patients alive, or to keep health care workers safe. Talking about “return to normal life” at this stage is stupyingly premature – PLEASE don’t bring this up for another month at minimum. People who have NOT adhered to social distancing / shelter in place / isolate when back from travel – for 14 days …. they all have forced extension of everybody’s current isolation time. Thank you very much, all you selfish ignorant people.
    New York is going to be decimated, LA is next. China was right, to be ultra rigorous in the full stop to people moving about. THAT curbed the spread. Italy was late, Spain was late – all docs there have been telling all other nations to hurry up and “shut down”. And they were late doing so. This is not just a virus. It is a virus that none of our health care systems can handle – unless we spread the inevitable occurrances (flatten the curve). But because of the initial delay to stop people travel / spreading disease, we (= everyone in the world not just in the US !) need to buckle down. There is no choice. And for the lofty goals in this article there won’t be enough tests for MONTHS to come yet. So please, no babble about how to return to normal. Normal is far beyond Easter that the delusional POTUS keeps pushing. Stay home, stay safe, and think of ways to help those on the front lines.

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