Yellow fever and several species of mosquitoes. In cities, it is spread primarily by "Aedes aegypti", a type of mosquito found throughout the tropics and subtropics. The virus is an RNA virus of the genus "Flavivirus". The disease may be difficult to tell apart from other illnesses, especially in the early stages. To confirm a suspected case, blood sample testing with polymerase chain reaction is required. A safe and effective vaccine against yellow fever exists, and some countries require vaccinations for travelers. Other efforts to prevent infection include reducing the population of the transmitting mosquito. In areas where yellow fever is common
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