Yellow fever is a zoonotic disease caused by an arbo–virus. It affects principally, monkeys and other vertebrates in tropical America and Africa, and is transmitted to man by certain culicine mosquitoes. It shares its clinical features with other viral hemorrhagic fevers (e.g. Dengue HF, Lassa fever etc). Severe cases develop jaundice with hemorrhagic manifestations (Black vomit, Epistaxis, Melena) and albuminuria or anuria, shock, agitation, stupor and coma. In general, death occurs between the fifth and tenth day of illness. The case fatality rate may reach 80% in severe cases. Survivors exhibit long–lasting immunity.

Problem statement
Yellow Fever in Africa
In Africa, yellow fever is prevalent between 15 degrees N and 10 degrees S. The endemic zone, defined by the presence of neutralizing antibodies, includes a total of 29 countries where epidemics occur at irregular intervals.

Yellow Fever in America
In the Americas, yellow fever is, at present, maintained enzootically in tropical forests, between 10 degrees N and 40 degrees S. Most cases are reported from Bolivia, Brazil, Colombia and Peru.

Paradoxically, there is no evidence that yellow fever ever has been present in Asia, where the closely related disease, Dengue is endemic. However, whether Dengue immunity would result in cross–protection against yellow fever in man is not certain, especially since yellow fever immunization and control does not protect against Dengue.