Yellow Fever Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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Yellow fever is a disease of the flavivirus family affecting humans and monkeys that is transmitted by mosquitoes of the genus Aedes. Yellow fever has long been associated with human-created ecological change, both in urban areas and, more recently, in areas of the tropics experiencing rapid deforestation and urbanization. Victims first develop fever, chills, and vomiting followed by internal bleeding and jaundice; the illness may lead to death within two weeks.

Medical historians believe that Aedes mosquitoes are native to West Africa and arrived in the Americas via slave ships beginning in the 16th century. The mosquito and the virus spread throughout North and South America, though in temperate regions Aedes could not overwinter but was frequently reintroduced through trade. Aedes is well adapted to urban environments, breeding in standing water as found in cisterns or tires. The virus exacted high mortality rates and caused social dislocation and economic isolation in the temperate-zone cities where it occurred periodically until 1905.

In the tropical regions where yellow fever was endemic, many experienced moderate cases as children and survived with immunity. Lack of immunity among Europeans and North Americans limited colonial activities in West Africa, foiled French plans to build a canal in Panama, and inhibited U.S. expansion in the Caribbean. These and similar frustrations inspired the development of the field of tropical medicine as an aid to the colonial project. Physicians Walter Reed and Carlos Finley in 1901 discerned that yellow fever was mosquito-borne, and the U.S. Army soon enforced mosquito control measures in Havana and other areas of interest. The same control methods allowed the United States to construct and defend the Panama Canal and brought an end to epidemics in North America.

Yellow fever has been largely eradicated in temperate regions and industrialized countries through quarantine, environmental control, mosquito eradication and, after 1937, vaccination. The Rockefeller Foundation implemented mosquito control measures worldwide in the interwar period, but vaccination delivered the final blow in many areas. Between World War II and the 1960s, public health and military campaigns worldwide used DDT to control Aedes. The Pan-American Health Organization attempted to eradicate one Aedes species throughout the Americas in the mid-20th century, but lack of U.S. support, and U.S. concern over DDT exposure, doomed the effort.

Yellow fever has reemerged as a threat in tropical regions of Africa and South America and now occurs there as epidemics as well as endemically. Comprehensive vaccination campaigns have protected regions such as The Gambia, but few states have achieved widespread vaccination. Infections have been increasing since the 1980s, with 200,000 cases and 30,000 deaths in 2000. Because several different Aedes species can transmit the virus, the disease can move among forest, savanna, village, and city environments. Timber workers have been exposed to the sylvatic form of yellow fever through mosquitoes that feed on forest-dwelling populations of several monkey species. Epidemiologists suspect that rapid, human-caused ecological change has resulted in outbreaks of an intermediate form of the disease at the edge of savannas and forests, and that the growth of cities in Africa and South America will increase epidemics of the urban form. Disease ecology experts in temperate regions fear that global warming will expand the range of Aedes mosquitoes and thereby yellow fever.

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