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.