Yellow fever epidemic of 1793

During the Yellow Fever Epidemic of 1793 in Philadelphia, 5,000 or more people were listed in the official register of deaths between August 1 and November 9. The vast majority of them died of yellow fever, making the epidemic in the city of 50,000 people one of the most severe in United States' history. By the end of September, 20,000 people had fled the city. The mortality rate peaked in October, before frost finally killed the mosquitoes and brought an end to the epidemic in November. Doctors tried a variety of treatments, but knew neither the origin of the fever nor that it was transmitted by mosquitoes (which was not verified until the late nineteenth century).

The mayor and a committee of two dozen organized a fever hospital at Bush Hill and other crisis measures. The assistance of the Free African Society was requested by the city and readily agreed to by the members, based on the mistaken assumption that native Africans would have the same partial immunity to the new disease as many had to malaria, the most common source of fever epidemics during the summer months. Black nurses aided the sick and the group's leaders hired additional men to take away corpses, which most people would not touch. Blacks in the city died at the same rate as whites, about 240 altogether. Some neighboring towns refused to let refugees in from Philadelphia, for fear they were carrying the fever. Major port cities such as Baltimore and New York had quarantines against refugees and goods from Philadelphia although New York sent financial aid to the city.

In the Spring of 1793, French colonial refugees, some with slaves, arrived from Cap Français, Saint-Domingue. The 2,000 immigrants were fleeing the slave revolution in the north of the island. They crowded the port of Philadelphia, where the first yellow fever epidemic in 30 years began in the city in August. It is likely that the refugees and ships carried the yellow fever virus and mosquitoes. It is transmitted during mosquito bites. The mosquitoes easily breed in small amounts of standing water. The medical community and others in 1793 did not understand the role of mosquitoes in the transmission of yellow fever and other diseases. Doctors and other survivors of the epidemic wrote extensively about it trying to learn from the crisis. (Many of their accounts are now available on-line, as is seen in the Primary Sources section below.)

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