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After 31 years of absence, yellow fever returned to Philadelphia, killing thousands of city residents over a span of several months. As the then-capital and largest city of the United States, Philadelphia was home to both local and federal governments, most of whose members (including President George Washington) fled to escape the disease. The total number of cases was estimated to be approximately 11,000; the final mortality rate for the city was 10%.

Like many others, Philadelphia physician Dr. Benjamin Rush (1745-1813) observed the symptoms and spread of the disease closely, hoping to uncover some definite cause and means of prevention. Rush kept meticulous notes about his individual patients as well as about conditions in the city for many years. His notes ranged from the observation that “A meteor was seen at two o’clock in the morning, on or about the twelfth of September” to several remarks that, curiously, “Moschetoes” were “uncommonly numerous.”

Rush, however, did not seem to draw any conclusions about the presence of the mosquitoes in relation to yellow fever. He favored the “miasma” theory of the disease—literally “pollution”—which was widely accepted in Philadelphia at the time. Miasmatic theory argued that diseases like yellow fever were the result of bad air. In 1793, its proponents blamed the yellow fever epidemic on the miasma from a shipment of rotting coffee that had been dumped at the docks.

Among the other comments Rush made in 1793 was one about refugees from the French West Indies escaping infection from yellow fever as it struck the city. Though Rush did not know it at the time, this was no doubt because the men and women who had come from the West Indies had been exposed to yellow fever before and were thus immune to it.

Unfortunately, Rush took a mis-step in his assessment of another group as being immune to the disease:

From the accounts of the yellow fever which had been published by many writers, I was led to believe that the negroes in our city would escape it. In consequence of this belief, I published the following extract in the American Daily Advertiser, from Dr. Lining’s history of the yellow fever, as it had four times appeared in Charleston, in South Carolina.

“There is something very singular (says the doctor) in the constitution of the negroes, which renders them not liable to this fever; for though many of them were as much exposed as the nurses to the infection, yet I never knew of one instance of this fever among them, though they are equally subject with the white people to the bilious fever.”

Shortly after the passage was published, Rush notes, Matthew Clarkson (1733—1800), the mayor of Philadelphia, wrote a response to the printer of the paper:

September 6th, 1793


It is with peculiar satisfaction that I communicate to the public, through your paper, that the African Society, touched with the distresses which arise from the present dangerous disorder, have voluntarily undertaken to furnish nurses to attend the afflicted; and that, by applying to Absalom Jones and William Gray, both members of that society, they may be supplied.



Tragically, as Rush noted, he had been mistaken in his belief that African-Americans would be immune to the disease:

"It was not long after these worthy Africans undertook the execution of their humane offer of services to the sick before I was convinced I had been mistaken. They took the disease in common with the white people, and many of them died with it."

Matthew Clarkson eventually fell victim to the disease as well: his gravestone notes that he “died of the fever in 1800.”

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