yellow fever

yellow fever, acute infectious disease endemic in tropical Africa and many areas of South and Central America. Yellow fever is caused by a virus transmitted by the bite of the female Aedes aegypti mosquito, which breeds in stagnant water near human habitations. A form of the disease called sylvan or jungle yellow fever is transmitted in tropical jungles by other species of mosquitoes that live in trees. Other primates are susceptible to the disease and function as a reservoir of the virus. Although the disease still occurs, typically in sporadic outbreaks, its incidence has been greatly reduced by vaccination and mosquito-control measures. The disease may be carried by travelers coming from endemic regions, and epidemics have extended into subtropical and temperate regions during warm seasons.

Yellow fever begins suddenly after an incubation period of three to five days. In mild cases only fever and headache may be present. The severe form of the disease commences with fever, chills, bleeding into the skin, rapid heartbeat, headache, back pains, and extreme prostration. Nausea, vomiting, and constipation are common. Jaundice usually appears on the second or third day. After the third day the symptoms recede, only to return with increased severity in the final stage, during which there is a marked tendency to hemorrhage internally; the characteristic “coffee ground” vomitus contains blood. The patient then lapses into delirium and coma, often followed by death. During epidemics the fatality rate was often as high as 85%.

The disease was highly prevalent in the Caribbean at the end of the 19th cent., and a way of controlling it had to be found before construction of the Panama Canal could be undertaken. In 1900 an American commission headed by Walter Reed and including James Carroll, Jesse Lazear, and Arístides Agramonte gathered in the U.S. Army's Camp Columbia in Cuba. Through their experiments—one of which severely sickened Carroll and killed Lazear—they proved the theory of C. J. Finlay that yellow fever was a mosquito-borne infection. Within the next few years, W. C. Gorgas, an army physician and sanitation expert, succeeded in controlling the disease in the Panama Canal Zone and other areas in that part of the world by mosquito-eradication measures. The last epidemic in the United States occurred in New Orleans in 1905; a severe outbreak in the Mississippi Valley in 1878 killed about 20,000. The development in 1936 of an immunizing vaccine (work on which won Max Theiler a Nobel Prize) and strict quarantine measures against ships, planes, and passengers coming from known or suspected yellow-fever areas further aided control of the disease.

See study by M. C. Crosby (2006).

See more Encyclopedia articles on: Pathology