Yellow Fever is found in the Americas, Europe and Africa, but is strangely absent from Asia. Formerly, it was quite important in both North and South America, including some cool - weather cities. Currently, it seems to be increasing in importance in Africa, making it not an emerging pathogen, but a re - emerging pathogen. This disease originated in Africa, and likely was introduced to the western hemisphere by the slave trade. In the 1600s – 1800s it caused epidemics in North American cities, including New Orleans, Philadelphia, New York, and Boston in the USA, and Halifax in Canada. Epidemics also occurred in Ireland, Wales, Spain, Uruguay, and Chile. It decimated Napoleon’s army in Haiti in 1802, causing the French to scale back their territorial ambitions in the New World. Yellow Fever virus was the first virus that was shown to be transmitted by a mosquito.
Yellow Fever cycles in both urban and forested (sylvan) environments, though the important hosts and vectors vary among locations. Primates (including grivet, Chlorocebus aethiops ; mangabeys, family Cercopithecidae; bush babies, family Galagidae; baboons, Papio spp.; and chimpanzees, Pan spp.) are the important wild hosts, and yellow fever can be fatal to howler monkeys, Alouatta spp; squirrel monkeys, Saimiri spp.; spider monkeys, Ateles spp.; and owl monkeys, Aotus spp. Typically, infection of monkey populations causes reduction in their density and collapse of the yellow fever epidemic, so the disease moves slowly through the population over a large area, returning after the population is replenished. Mortality among monkeys is much less common in Africa than in the Americas. Other animals such as the anteaters Tamandua tetradactyla and Cyclopes didactylus ; kinkajou, Potos flavus ; and various rodents may be involved as hosts, but their importance is uncertain.
Affected animals display fever, vomiting, pain, dehydration, and prostration, and sometimes hemorrhage including renal failure and death. Human infection produces similar maladies, including liver damage (resulting in jaundice, hence the name ‘ yellow fever ’ ), and up to 75% of affected humans die.
The mosquito Aedes aegypti is often called the yellow fever mosquito due to its association with yellow fever, particularly in urban situations. Aedes aegypti is particularly dangerous due to its affinity for houses, where it enters and feeds while the inhabitants sleep. Although eliminated from South America in the 1930s and 1940s, A. aegypti has recovered and now poses a significant threat to South American urban areas due to its association with yellow fever. In sylvan (forested) sites of the Americas, other Aedes spp., Haemagogus spp., and Sabathes chloropterus are the important vectors. In Africa, other Aedes spp. and Dicermyia spp. transmit the virus among monkeys and to people. Antimosquito programs have brought yellow fever under control in many urban areas, but in rural areas it remains a threat. It is sometimes referred to as ‘ woodcutter ’ s disease ’ due to its association with forested environments and the people who work there.
