Yellow fever cycle, both in Africa and South America, a sylvatic cycle (forest or jungle cycle) is present, where "Aedes africanus" (in Africa) or mosquitoes of the genus "Haemagogus" and "Sabethes" (in South America) serve as vectors. In the jungle, the mosquitoes infect mainly nonhuman primates; the disease is mostly asymptomatic in African primates. In South America, the sylvatic cycle is currently the only way humans can become infected, which explains the low incidence of yellow fever cases on the continent. People who become infected in the jungle can carry the virus to urban areas, where "A. aegypti" acts as a vector.
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