The city of Wuhan, China, where Covid-19 started, waited weeks before acknowledging human-to-human transmission and taking measures to control it. Wuhan thus experienced an out-of-control epidemic that overwhelmed the health care system. The city felt these effects for weeks after intense control measures were in place, as newly infected people got sick and required care.
Other cities in China watched Wuhan’s experience and imposed strict controls at a much earlier stage in their epidemic: They closed schools, sharply limited social contact, and traced and isolated cases and contacts. These early interventions dramatically slowed transmission. No other Chinese city has repeated Wuhan’s horrific experience so far. Now other hotspots of known transmission, including Iran and Italy, are tightly restricting social contact, but these interventions are coming late, and hospitals are teetering under the stress.
These experiences, and historical parallels, like the 1918 flu, show that early and sustained imposition of measures to limit social contact will slow the epidemic. This is desirable for many reasons — fewer total people get infected in a slowly moving epidemic; those who do get infected do so later, on average, so doctors will have learned more about how to care for the illness, and antiviral drugs may even be available. Most important in light of Wuhan’s crushing experience, a controlled epidemic has a lower peak, reducing the strain on health systems. From the perspective of disease control, every effort should be made, as soon as possible, to slow the spread of the virus and flatten the epidemic curve. If these interventions are not sustained, spread will resume, but every action to slow it buys us some time and probably reduces the total size of the outbreak.
Many kinds of mitigation measures are needed immediately. Case-based interventions to isolate confirmed cases and trace and quarantine their contacts are already overwhelming some US health departments, consuming time and resources that could be better spent on implementing social distancing and trying to soften the blow of its effects. These case-by-case measures are unlikely to do much on their own when we know most cases are going undetected. Instead, we must focus on reducing social contacts in order to slow transmission, by keeping people at home and out of public spaces. Conventions, parades, sports events, and other large public gatherings that risk transmission should be canceled or postponed. Efforts to reduce contacts should focus on the most vulnerable (elderly and those with certain serious chronic medical conditions), but not be restricted to them, because all of us can become infected and transmit the virus, even without severe symptoms. Working from home, staying home when sick, hand-washing, covering coughs, and the like are all common-sense ways to reduce contacts and slow spread. Building ventilation should be improved wherever possible. The shameful lack of soap and hot water in many public school buildings needs to be fixed. Suspending public transportation, houses of worship, and other close quarters may soon be needed.
Many businesses and individuals are already canceling travel plans. This may be wise because travel involves close quarters with many people on planes and trains, and because much business travel revolves around attending large meetings. But it’s wrongheaded at this stage to talk about “lockdowns” to prohibit travel to and from particular places where many cases have been found, as US government officials have done recently. Currently, we have little idea what locations in the United States are hotspots of transmission — testing has been so limited that we know about cases mainly after someone gets so sick that they are tested for Covid-19. For now, the hotspots in the United States are the places that have done the most testing.
One intervention where the way forward is less clear is school closings. School closings clearly hamper transmission of seasonal and pandemic flu; some evidence also exists for other respiratory viruses. Some districts in the United States are closing schools now. What role will this play in controlling the spread of SARS-CoV-2, the virus that causes Covid-19?
The data are limited and conflicting. Reports from China on over 44,000 cases suggested just 2.4 percent of confirmed cases were in children under 19. Korea, which has tested more widely, had twice that proportion, but still low case numbers in children. A study in Shenzhen, China, while smaller, found that children were just as likely to get infected as other age groups. It is clear that children have milder symptoms than adults, and it seems that studies that look harder, testing more and milder cases, find more cases among children. This suggests that children may play a role in transmission, perhaps less important than in flu, but still important. More research is desperately needed, but we may not have time to get compelling answers before decisions are needed. The decision on school closure will come down to a choice between two bad options.
Closing schools may be a major contribution to controlling the epidemic spread, but we can’t be sure. Closing schools, however, has multiple costs — lost education, loss of essential workers, including medical and public health workers who need to care for their children if schools are closed, loss of school meals and mental health services, and other harms that will disproportionately hit the least advantaged.
The Biogen outbreak should help us realize that we are on the brink of experiencing a public health catastrophe. The examples of Wuhan, Italy, South Korea, Japan, and Iran should give us all a strong resolve to slow the epidemic before it is too late. Every intervention we try will be testing new waters, and evaluation is critical to make sure that, as we impose costs on society, we are getting the benefits of disease control. Just as important as when to act is when to let up on control measures. But we must act now.
Dr. Marc Lipsitch is a professor of epidemiology and director of the Center for Communicable Disease Dynamics at the Harvard T.H. Chan School of Public Health.
Have a point of view about this? Write a letter to the editor; we’ll publish a select few. (We’re experimenting with alternatives to the comment section for creating online conversation at Globe Opinion over the next month; you can let us know what you think of our experiments here.)