Yellow fever (also called black vomit or sometimes The American Plague) is an acute viral disease. It is still an important cause of hemorrhage illness in several African and South American countries despite existence of an effective vaccine. In the past it was a source of several devastating epidemics.

The disease is caused by an arbovirus of the family Flaviviridae, and is one of the smallest RNA viruses isolated from man.

Mosquitos are the primary in transmission of the disease from forest monkeys to man and in man-to-man transmission. The mosquitos involved are Aedes simpsoni , Aedes africanus , and Aedes aegypti in Africa; and the Haemagogus and Sabethes genera.

The course of the disease varies from an inapparent infection to an intense feverish illness with high mortality rate. There is a difference between disease outbreaks in rural or forest areas and in towns. Disease outbreaks in towns and non-native people are usually more serious.

After a 3 to 6 day incubation period the typical symptoms that arise are fever, muscle aches, headache and backache. Other symptoms may include a red tongue, flushed face, and reddening of the eyes may also be symptoms of the disease. In a proportion of cases there is also involvement of internal organs - liver, kidneys and the heart. There may be hemorrhage from the digestive tract (bloody vomit). Later the disease is sometimes complicated by jaundice with liver failure and/or renal insufficiency with proteinuria. If the disease progresses, delirium, seizures and coma ensue. Hypotension and dehydration are also common. Mortality is around 5%. Patients who die usually do so within six to seven days from the onset.

Prevention

A vaccine for yellow fever was developed which gives a 10-year+ immunity from the disease and effectively protects people travelling to the affected areas whilst being a means to control the disease at the same time. Insecticides, protective clothing and screening of houses are helpful but not always enough. In affected areas mosquito control methods have proved effective in decreasing the number of cases.

Treatment

There is no specific cure for the disease; therefore vaccination is so important. Treatment is symptomatic and supportive only. Fluid replacement, fighting hypotension and transfusion of blood derivates is mostly needed in severe cases. In renal insufficiency - dialysis. A fever victim needs to get lots of rest, fresh air, and drink plenty of fluids.

History

The Yellow Fever has had several important roles in the history of the Americas and the Caribbean. In the early 19th Century an army of 40,000 sent by First Consul Napoleon Bonaparte of France to Haiti to suppress the Haitian Revolution was wiped out by an epidemic of Yellow Fever (including the expedition's commander and Bonaparte's brother-in-law, Charles Leclerc). Some historians believe Haiti was to be a staging point for an invasion of the United States through Louisiana (then still under French control).

In addition the first failed attempts to build the Panama Canal (by a French company) were thwarted in part due to the huge number of deaths amongst workers caused by the Yellow Fever. The vaccination for the fever was first formulated during the second attempt to build the canal.

References

• Theiler, Max and Downs, W. G. 1973. The Anthropod-Borne Viruses of Vertebrates: An Account of The Rockefeller Foundation Virus Program 1951-1970. Yale University Press.
• Downs, Wilbur H., et al. 1965. Virus diseases in the West Indies. Special edition of the Caribbean Medical Journal, Vol. XXVI, Nos. 1-4, 1965

Other meanings

Yellow fever is sometimes used (generally disparagingly) to refer to men having a sexual fetish for Asian women.

See also: Lassa fever, Dengue fever.