John Mulhall is a PhD candidate in history at Harvard University, a Tyler Fellow at Dumbarton Oaks and a member of the Max Planck-Harvard Research Center for the Archaeoscience of the Ancient Mediterranean.

As the world fights the coronavirus, we are going to battle with medieval weapons.

The Middle Ages gets a bad rap, especially when it comes to health. Images of filth, barbarity and quackery come to mind, reinforced by the silverware-free meals of Renaissance fairs and the spoofs of “Saturday Night Live” and Monty Python (“She turned me into a newt — I got better!”).

Despite this reputation, we have the Middle Ages to thank for some of the most enduring advances in public health and medicine. In the crucible of the bubonic plague, which struck Europe in 1347 and recurred periodically for more than two centuries, our medieval forebears forged weapons against disease that remain our most effective tools for combating covid-19.

Bubonic plague is a horrific disease. Only recently was the identity of the medieval pandemic confirmed, thanks to ancient DNA preserved in the bodies of its victims. Yersinia pestis, the bacterium that causes plague, has evolved to survive among rodents, spreading to humans primarily through fleas. In modern cases of plague, about half of untreated patients die, usually three to five days after showing symptoms, making the disease around 25 to 50 times deadlier than covid-19.

In the face of this horror, as 14th-century death counts stretched into the tens of millions, prayers were a natural reaction. But the devout beliefs of medieval physicians, trained in universities around Europe, in no way prevented them from seeking the plague’s more immediate, natural causes. Through careful observation, many physicians came to recognize that the disease could be spread from person to person, and they worked with civil governments to develop a response.

The city of Milan led the way. In the 1370s, Milan began separating the sick from the healthy and instituted self-quarantine measures. Those in close contact with the sick were required to isolate themselves for 10 days. As successive waves of plague hit the city, Milan’s epidemiological defenses became more elaborate. Plague hospitals were opened. Pilgrims passing through Milanese territory were detoured around the city itself, and camps were set up to keep travelers housed and fed without having to enter densely populated areas.

Most impressive was Milan’s detailed monitoring of cases. Physicians appear to have been quite skilled at recognizing plague symptoms, developing detailed criteria for discerning plague buboes from other, less deadly swellings. They identified patients who needed to be isolated and reported this information, along with a list of all deaths, to city authorities. These reports kept the city a step ahead of the disease, allowing its government to ramp up measures of isolation when the plague was on the rise and relax such measures when the plague had disappeared from the city.

Cities of that era faced tough choices that now appear all too familiar. Was it better to prohibit foreign trade and risk financial disaster, or should economic life continue at the risk of more contagion? Medieval ingenuity offered a plan. In the late 15th century, physicians in Milanese territories began issuing documents testifying to an individual’s well-being. Relying on these “health passes” — precursors to our modern antibody tests — medieval cities could close travel and trade to all but those who had been examined and deemed, using the best criteria available, to be free of the plague.

Milan was not the only medieval city to develop such innovative measures — for example, in 1377, Ragusa (modern-day Dubrovnik, Croatia) instituted one of the earliest quarantines in human history. But Milan’s fight against the pandemic cannot be matched in its ingenuity or thoroughness.

The key to its success lay in the decisive executive action of Milan’s ruling dukes. Skilled physicians were essential, but what separated Milan from other states was a government that put the physicians’ talents to best use.

This collaboration is precisely what our response to covid-19 requires. Developed nations, including the United States, cannot rely solely on world-class physicians. If executive authority is not deployed in collaboration with the best medical knowledge available, we deny ourselves the tremendous potential of testing, case monitoring and contact tracing. The rulers of Milan understood this concept, as do modern nations such as South Korea and Taiwan.

In 2020, we aren’t in uncharted territory. Thus far, we have wisely armed ourselves with the medieval weapons of quarantine, self-isolation and, in some cases, monitoring. But we’re behind even 15th-century Milan when it comes to the modern equivalent of “health passes.” Unlike Milan, however, we have today the benefit of historical experience. Just as we rely on the invaluable advances of modern medicine, we ought to avail ourselves of the tools developed at great cost by those who suffered the pandemics of the past.

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