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
Yellow fever viruses. The main vector ("A. aegypti") also occurs in tropical and subtropical regions of Asia, the Pacific, and Australia, but yellow fever has never occurred there, until jet travel introduced 11 cases from the 2016 Angola and DR Congo yellow fever outbreak in Africa. Proposed explanations include: But none is considered satisfactory. Another proposal is the absence of a slave trade to Asia on the scale of that to the Americas. The trans-Atlantic slave trade probably introduced yellow fever into the Western Hemisphere from Africa. The evolutionary origins of yellow fever most likely lie in Africa, with transmission of the