Coronavirus has become political. Conservative media has promoted the idea that the disease is a “Coronavirus Impeachment Scam.” President Trump has encouraged his supporters to ignore medical experts and has downplayed their recommendations — at least before this week, when he abruptly changed tone. His press secretary has claimed Democrats are using the virus to “politicize things and scare people.” A recent poll shows more than three out of four Republicans believe the media has exaggerated the risk of the virus.

But public health should not be political. In early America, it usually was not. But in 1793, politics and public health mixed, with dangerous consequences. During a massive outbreak of yellow fever in the nation’s then-capital city, Philadelphia, members of the earliest parties in the United States took advantage of medical uncertainty to advance partisan agendas. They developed conflicting explanations for the outbreak, and different proposals for how to respond to it. The politicization of this crisis distracted from the treatment of victims and ultimately harmed efforts to prevent the spread of the fever.

To many Philadelphians, the 1793 yellow fever epidemic may have seemed like the end of the world. Scores died each day. Tens of thousands of people fled the city. Other people refused to leave their homes, fearing contact with others.

Based on the fallacious belief that people of African descent were immune to yellow fever, the city’s black community tended to the sick and buried the dead — sometimes more than 100 people a day. By the late summer and early autumn, around 10 to 15 percent of the city’s people had died.

At the same time, partisanship began to divide Americans for the first time. The emerging Federalist party, led by men such as George Washington, John Adams and Alexander Hamilton, feared that revolutionary events abroad such as the French and Haitian Revolutions were producing dangerous seeds of anarchy that might spread to the United States. On the other hand, members of the nascent Republican Party, led by Thomas Jefferson and James Madison, were more sympathetic to the French Revolution, and in some cases to the early stages of the Haitian Revolution.

In addition to being the new nation’s political capital, Philadelphia was the center of institutional medicine in 18th-century America. Seeking to prevent further spread of the epidemic, the city’s physicians developed a few theories of the outbreak’s origin. Though many physicians claimed to, no one really understood yellow fever, its transmission or treatment options.

One group of doctors believed that the yellow fever outbreak developed as a result of the city’s poor sanitary conditions, local swamps or the surrounding climate. The city’s Republicans, many of whom despised urban areas and envisioned the United States as a nation of small farmers, generally aligned themselves with this explanation.

Another group of physicians, though, blamed outsiders — especially the large numbers of refugees from France or revolutionary Haiti (then called Saint Domingue) — for bringing the yellow fever into the city. Fearful of foreigners, and especially fearful of people coming from France and Haiti, Federalists gravitated toward this “importationist” theory. Some spread a conspiracy theory that the refugees had intentionally caused the outbreak by poisoning the city’s wells in advance of an invasion from revolutionary France. Federalists used the pestilence to their political advantage by trying to close the city off from France and the French Caribbean.

Neither the Republicans nor the Federalists were entirely correct, though there was merit in each of their theories. In the early 20th century, doctors discovered that mosquitoes transmit yellow fever, and that it is not transmissible between humans. More recently, historian Billy G. Smith has shown that the arrival of a ship called the Hankey probably brought water casks from Saint Domingue containing mosquitoes that spread the epidemic. But these mosquitoes thrived and spread the disease because they were able to breed in local swamps.

Political controversy over the yellow fever outbreak did not end with debates over its causes. Philadelphians also disagreed about the proper treatment of the disease. Though doctors proposed many different kinds of cures, there were two main competing schools of thought. Some doctors proposed using stimulants including quinine bark, while others suggested a newer treatment that involved drawing large quantities of blood and administering mercury. Though initially nonpartisan, this dispute over treatment eventually took on political dimensions as the city and its medical community polarized.

In part, this was because the city’s most eminent proponent of the bloodletting treatment was the doctor Benjamin Rush, who was affiliated with the Republican Party and despised by many Federalists. Rush’s politics may have shaped his approach to treatment. Like many of his fellow Republicans, Rush was committed to an egalitarian approach to knowledge. Drawing on long-standing practices in times of emergency, he declared one didn’t need a college education to treat yellow fever by bloodletting, and published do-it-yourself guides for the use of untrained people, critical given the lack of healthy doctors.

Federalist critics’ politics likewise shaped their view of Rush’s plan. They charged that Rush’s bloodletting was akin to the bloody scenes taking place in Paris, where the Reign of Terror was underway. Rush himself later remembered, “I ascribe the opposition to my remedies … chiefly to an unkind and resentful association of my political principles with my medical character.”

While many Republican physicians rejected Rush’s methods, his prominence contributed to the perception that the use of stimulants was the “Federalist cure,” and the use of bloodletting was the “Republican cure.” Eventually, this perception took on a life of its own. The idea that there were Federalist and Republican “cures” for yellow fever snowballed from there. Earnest critics of Rush’s dangerous treatment, which was more harmful than treatment with stimulants, risked being labeled as anti-Republican partisans. These political associations may have helped to sustain Rush’s harmful “cure” longer than it deserved.

While some of these “treatments” were more counterproductive than others, none of them was effective. In fact, there remains no cure for yellow fever today, even as medical knowledge has advanced by leaps and bounds. Perhaps for that reason, no expert consensus formed about the outbreak. Doctors and institutions genuinely disagreed on the origins and treatment of the disease. This division allowed partisan politics to consume the yellow fever outbreak, distracting from efforts to understand it and ameliorate the symptoms of the afflicted.

Today, there is no such division among doctors. Modern medical professionals understand coronavirus far better than 18th-century doctors understood the yellow fever, and there is a widespread international consensus for preventing and treating it. Yet popular distrust toward expertise, and perhaps a desire to avoid panic in an election year, has created a condition similar to 1793 Philadelphia. The medical community’s consensuses surrounding coronavirus have not prevented Americans from politicizing it.

Already, according to recent polling, partisans are reacting differently to the virus. Democrats are significantly more likely than Republicans to fear an imminent threat from covid-19. In greater numbers, Democrats are changing travel plans, altering daily habits and taking preventive measures. As with climate change, it seems that coronavirus has become absorbed within the broader landscape of partisan political warfare. But as the Philadelphia yellow fever epidemic suggests, this is ultimately a dangerous distraction. The stakes of deadly disease are too high to rely on partisan sources of knowledge.