The search for the cause of yellow fever reveals a lot about the early American republic.
In August 1793, pestilence struck Philadelphia, the political capital of the nascent United States and its center of economic, cultural, and scientific activity. Those stricken exhibited high fever, chills, and delirium; in the worst cases, their skin turned yellow, and they emitted the infamous “black vomit,” a foul mixture made of partially digested blood that had hemorrhaged from the organs. Doctors who attended the sick identified the disease as yellow fever, a wasting illness that usually prevailed in tropical environments and struck down as many as half of those afflicted. By November, when the fever finally relented, more than four thousand people had died. Those who survived hoped that it would never return.
With the future of the republic hanging in the balance, thinkers hoping to prevent the disease posed a deceptively simple question: What caused yellow fever?
To the consternation of Americans, yellow fever reappeared annually from 1793-1805. The disease killed thousands in Philadelphia and New York, and hundreds more in Boston, Baltimore, Charleston, and New Orleans. Yellow fever was the most pressing natural problem of the era. Besides the deaths, the fever incited frantic mass evacuations. It halted trade in the nation’s busiest commercial centers for months at a time and led to burdensome quarantines and expensive sanitary reform measures. To many, yellow fever also seemed to erode public virtue, the cornerstone of a healthy republic, as fearful citizens turned against each other. For many others, the fever constituted a direct challenge to American exceptionalism, the pervasive belief that Americans were God’s people and were destined to escape the cycles of history that doomed past peoples.