Yellow fever yellow fever because of the vast number of infected mosquitoes in urban areas of the target countries, but it will significantly reduce the number of people infected. Demand for the yellow fever vaccine has continued to increase due to the growing number of countries implementing yellow fever vaccination as part of their routine immunization programmes. Recent upsurges in yellow fever outbreaks in Angola (2015), Democratic Republic of Congo (2016), Uganda (2016), and more recently in Nigeria and Brazil in 2017 have further increased demand, while straining global vaccine supply. Therefore, to vaccinate susceptible populations in preventive mass immunization campaigns during
Yellow fever disease from nonhuman primates to humans. 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. This phenomenon, in which certain populations develop immunity to yellow fever due to prolonged exposure in their childhood, is known as acquired immunity. The virus, as well as the vector "A. aegypti," were