As the coronavirus crisis has evolved into a global public-health emergency over the past few months, the virus and its resulting disease, COVID-19, have increasingly been compared to the influenza epidemic of 1918, which ultimately claimed the lives of between twenty and forty million people worldwide, including an estimated six hundred and seventy-five thousand in the United States. In a feature in The New Yorker, in 1997, Malcolm Gladwell wrote that, in the fall of 1918, the influenza had “reached every continent and virtually every country on the map, going wherever ships sailed or cars or trucks or trains travelled, killing so many so quickly that some cities were forced to convert streetcars into hearses.” The coronavirus, too, has touched every corner of the globe. As of Wednesday morning, according to the World Health Organization, there have been nearly eight hundred and twenty-four thousand confirmed cases, resulting in more than forty thousand deaths. Public-health officials, epidemiologists, and other experts expect these figures to increase: graphs of coronavirus infections to date show a line arcing exponentially upward, nowhere close to flattening out—as our collective public-health goal is now articulated.

The physician and medical historian Howard Markel, who teaches at the University of Michigan, has studied the 1918 epidemic extensively, and has written about strategies that successfully mitigated its devastation in certain areas. In a paper published in JAMA, in 2007, Markel and his team describe how certain cities in the U.S. fared far better than others owing to their stringent use of nonpharmaceutical interventions (N.P.I.s), including social distancing. In the video above, speaking with the New Yorker staff writer Isaac Chotiner, Markel explains the ways in which the response to the flu epidemic a century ago can influence decision-making today. “[The 1918 epidemic] is the largest database of this menu of social distancing, specifically quarantine and isolation, school closure, and public gatherings,” Markel says. His 2007 paper specifies, as Chotiner quotes, that “neither the city’s population size, density, sex distribution, nor age distribution accounted for the differences in mortality.” But, when communities implemented early, sustained combinations of practices such as social distancing, Markel says, “we simply saw . . . fewer deaths in those cities.”

“The key word about this coronavirus is ‘novel’—we don’t have any experience with COVID-19,” he continues. “We won’t know it’s over until long after it’s over, so it’s hard to know when to release the trigger.” However, he says, “This I know: if we release these measures too early, we’re going to be back in the same situation that we were in, in terms of cases and deaths, or perhaps worse, and we will have crippled the economy and caused all this social disruption for nothing.”

A previous version of this post incorrectly referred to an earlier paper by Markel and his team.

A Guide to the Coronavirus