The yellow fever outbreak in Philadelphia most likely came to the city by refugees fleeing a slave revolt in Santo Domingo (modern-day Haiti). Between 1791 and 1803, the people of Haiti fought for their independence from France, making Haiti the second independent country in the Americas (after the United States) and the first founded by former slaves. Yellow fever, carried by mosquitos, was a regular occurrence in Haiti.
Learn more about the Haitian Revolution in Gilder Lehrman's video featuring Duke University historian Laurent Dubois:
Objects and Images Related to 1793 Yellow Fever Epidemic
(Click images for more information)