Yellow fever
Yellow fever (also called
black vomit or sometimes
The American Plague) 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 of the
family Flaviviridae, and is one of the smallest RNA viruses isolated from man.
Mosquitos are the primary disease vector 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.
Public health
\nYellow fever is one of the few diseases in the world for which some countries have a legal requirement for vaccination for someone travelling to an affected area. There countries also usually have regulations requiring quarantine for people who arrive from yellow fever endemic areas who do not provide evidence of their having being vaccinated against yellow fever. This is because the vector for transmission of yellow fever, the Aedes mosquito, exists in other tropical parts of the world which are not affected by yellow fever and an outbreak could potentially erupt if the disease is inadvertently brought in.
Prevention
\nA 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.
In many countries, visitors who have been to yellow fever endemic areas within the last six months who do not have documentary proof of vaccination to yellow fever are liable for quarantine until they are proven to be clear of yellow fever.
Treatment
\nThere is no specific cure for the disease; therefore vaccination is so\nimportant. 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.
\nCategory:Infectious diseasesCategory:Virology
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