[I]n order for a pandemic to end, the disease in question has to reach a point at which it is unable to successfully find enough hosts to catch it and then spread it.
By the end of the [1918 Spanish flu] pandemic, a whopping third of the world’s population had caught the virus. (At the moment, about half a percent of the global population is known to have been infected with the novel coronavirus.)
The end of the 1918 pandemic wasn’t, however, just the result of so many people catching it that immunity became widespread. Social distancing was also key. Public health advice on curbing the spread of the virus was eerily similar to that of today: citizens were encouraged to stay healthy through campaigns promoting mask-wearing, frequent hand-washing, quarantining and isolating of patients, and the closure of schools, public spaces and non-essential businesses—all steps designed to cut off routes for the virus’ spread.
In fact, a study that [physician Howard] Markel and [historian Alexander] Navarro co-authored, published in the Journal of the American Medical Association in 2007, found that U.S. cities that implemented more than one of these aforementioned control measures earlier and kept them in place longer had better, less deadly outcomes than cities that implemented fewer of these control measures and did not do so until later.