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Yellow fever

Yellow fever is an acute viral disease. It is still an important cause of hemorrhagic 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[?] (Flaviviridae), one of the smallest RNA viruses isolated from man.

Mosquitos are the primary disease vector in transmission of the disease from forrest [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. The form of disease in towns and non-native people being a more serious one.

After a 3 to 6 day incubation period there are fever, muscle aches, headache and backache. 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. Then it may occur bleeding tendency from the digestive tract (bloody vomit) and to the skin. 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. Patients usually die within six to seven days from the onset. Nowadays mortality is variable usually around 5%.

Prevention

Fortunately a vaccine was developed and it gives a 10-year immunity from the disease and effectively protects people travelling to the affected areas and 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 some sort of mosquito control has proved effective in decreasing 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.

See also : Lassa fever.



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