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.
1793 Philadelphia yellow fever epidemic atmosphere that might last 50 years and make deadly epidemics almost certain. Yellow fever epidemics became seen as a national crisis. When in 1855 a French doctor published an 813-page history of yellow fever in Philadelphia, covering outbreaks from 1699 to 1854, he devoted only a few pages to the 1793 epidemic. General 20th-century US histories, such as the 10-volume "Great Epochs in American History," published in 1912, used short excerpts from Carey's account. The first history of the epidemic to draw on more primary sources was J. H. Powell's "Bring Out Your Dead" (1949), but he did not use