1793 Philadelphia yellow fever epidemic immune to the fever. Many of the slaves in Charleston in 1742 could have gained immunity before having been transported from Africa, by having been exposed to yellow fever in a mild case. People who survived one attack gained immunity. A total of 240 blacks died, in proportion to their population at the same rate as whites. Given the limited resources and knowledge of the times, the city's response was credible. The medical community did not know the natural history of yellow fever, a viral infection spread by the "Aedes aegypti" mosquito. Efforts to clean the city did not defeat
Yellow fever probably transferred to North and South America with the importation of slaves from Africa, part of the Columbian Exchange following European exploration and colonization. The first definitive outbreak of yellow fever in the New World was in 1647 on the island of Barbados. An outbreak was recorded by Spanish colonists in 1648 in the Yucatán Peninsula, where the indigenous Mayan people called the illness "xekik" ("blood vomit"). In 1685, Brazil suffered its first epidemic, in Recife. The first mention of the disease by the name "yellow fever" occurred in 1744. McNeill argues that the environmental and ecological disruption caused by