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The evolutionary origins of yellow fever most likely lie in Africa, with transmission of the disease from non-human primates to humans.[45][46] The virus is thought to have originated in East or Central Africa and spread from there to West Africa. As it was endemic in Africa, the natives had developed some immunity to it. When an outbreak of yellow fever would occur in an African village where colonists resided, most Europeans died, while the native population usually suffered nonlethal symptoms resembling influenza.[47] This phenomenon, in which certain populations develop immunity to yellow fever due to prolonged exposure in their childhood, is known as acquired immunity.[48] The virus, as well as the vector A. aegypti, were 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.[49] 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.

Source: Wikipedia