If locking down entire populations is an unparalleled global experiment in disease control, so is releasing them.
Scientists studying the novel coronavirus say that without a vaccine or widespread immunity it is almost inevitable that easing lockdown measures in Europe and the U.S. will trigger second or even multiple waves of infection. China, Singapore, South Korea, Iran and Germany are among a handful of countries that have seen signs of the virus re-emerging to varying degrees as stringent containment measures have been relaxed.
So far, the number of new cases in these second waves has been small. But the prospect of a severe resurgence has sent researchers scrambling to determine how best to prevent any trickle of new infections turning into a flood as hibernating economies are brought back online. The “Spanish flu” pandemic that began in 1918 killed more people world-wide in its second wave than in the first.
Disease experts’ clearest message: Governments must scale up testing to identify the infected, trace those with whom they have been in contact, and isolate those individuals to impede the virus’s spread. “Test, trace, isolate is a kind of old adage in epidemiology,” said Joshua Moon, a researcher in global health emergencies at the University of Sussex, U.K.
Policy makers, though, must make dozens of other judgments. Should schools reopen, and if so with what safeguards for staff and pupils? Should people wear masks when going about their daily lives? Should the elderly and other vulnerable groups cocoon themselves at home for months to come? And if so, how should those caring for them best shield them from the virus?
Scientists are examining these and other questions to advise governments on how to keep transmission of the virus low and prevent the need to reverse course on lockdowns. But data are limited, the precedents are in Asia where most countries started and ended lockdowns with fewer cases than in the West, and studies sometimes reach conflicting conclusions.
Only by gently easing the stringent measures that reduced the spread of the virus can we improve our understanding of what works and what doesn’t, they say.
“There’s so much uncertainty,” said Mike Tildesley, an associate professor in life sciences at the University of Warwick in England, who models infectious diseases. “As we start to relax, we will get more information. But that’s a really hard sell to the public.”
Most European countries are now gradually easing monthslong lockdowns after growth in case numbers and fatalities has slowed. So are many U.S. states. The economic cost in jobs and income lost to the restrictions is expected to dwarf the losses of the financial crisis a decade ago. In March and April alone, employers in the U.S. shed more than 21 million jobs. The economies of France, Spain and Italy reported record falls in output during the first quarter.
Public-health officials are urging policy makers to relax restrictions cautiously. In Senate testimony this week, Dr. Anthony Fauci, the U.S. government’s leading infectious diseases doctor, told senators to brace for more infections. “There is no doubt that when you pull back on mitigation, you will see some cases reappear,” he said Tuesday, warning that the country faces “needless suffering and death” if the nation reopens too rapidly.
There have been more than four million confirmed cases of coronavirus infection since the virus was first detected in China late last year. Almost 300,000 deaths have been linked to Covid-19, the disease it causes. The majority have been in Europe and the U.S.
A lot is still unknown about the pathogen, complicating efforts to safely ease restrictions. Scientists still aren’t sure, for example, how many people world-wide have really been infected. That means estimates of how lethal it is vary. Nor do they know whether the immunity that usually occurs after infection is lasting or fleeting. Why some outwardly similar countries suffer serious outbreaks and others don’t isn’t fully understood.
As the disease has spread, data on its effects have multiplied and a few clearer signals have emerged. Perhaps the strongest is that children predominantly suffer only mild symptoms if infected with the virus. Their role in transmission of the bug is less clear but that has given many countries, including Denmark and Germany, the confidence to begin reopening schools, albeit with extra hygiene measures and smaller classes.
Public-health authorities have also increasingly swung behind the idea that face masks can be helpful in impeding transmission. The Centers for Disease Control and Prevention provides an easy guide to making a homemade mask on its website. A review of 84 studies published online and awaiting peer review looked at the effectiveness of face masks in limiting the spread of the virus and concluded that governments should strongly encourage their regular use.
One advantage of the ballooning amount of data on Covid-19 is that disease experts can increasingly rely on abundant real-world observations to guide policy and not just on computer models. By melding modeling and actual European case data, researchers at the U.K.’s University of East Anglia determined that school closures, banning mass gatherings and closing businesses early in the outbreak worked well to stanch the spread of the disease. In a surprise finding, they concluded stay-at-home orders had little additional impact on disease spread.
The still-developing picture of which measures are most effective means countries easing out of lockdown are taking different approaches to containing the virus. Elementary schoolchildren may have returned to class in Denmark and Germany but not in Spain or Italy. In the U.S., states including Florida and Indiana have allowed nonessential businesses adhering to hygiene and social-distancing guidelines to reopen, while in California and Illinois they remain closed.
Epidemiologists say the gaps in our knowledge of the virus reinforce the need for effective test, trace and isolate programs to locate and quarantine infected individuals. The more effective those systems are, the more scope there is for relaxing social-distancing measures, said Mark Woolhouse, professor of infectious disease epidemiology at the University of Edinburgh. Some countries are experimenting with cellphone apps to alert citizens to the proximity of suspected cases.
One potential wrinkle for the West: In China, though the virus reached Beijing and Shanghai, it was mostly contained in Hubei province and its capital Wuhan, the city of 11 million where the outbreak started. Elsewhere in Asia, case levels at the start and end of lockdowns were lower than in the West. In the U.S. and some European countries such as the U.K., the disease is more dispersed, with cases and deaths reported in major urban centers countrywide, making it possible for clusters of new infections to spring up and proliferate at the same time.
That could stretch tracing systems and give the virus a chance to spread. “If a fire is confined to your chip pan there’s a chance of putting it out. Leave it one minute and it’s got your kitchen,” said David Leon, professor of epidemiology at the London School of Hygiene and Tropical Medicine.