Yellow Fever

Yellow fever (also known as Yellow Jack and Bronze John) is an acute viral hemorrhagic disease. The virus is a 40 to 50 nm enveloped RNA virus with positive sense of the Flaviviridae family.

The yellow fever virus is transmitted by the bite of female mosquitoes (the yellow fever mosquito, Aedes aegypti, and other species) and is found in tropical and subtropical areas in South America and Africa, but not in Asia. The only known hosts of the virus are primates and several species of mosquito. The origin of the disease is most likely to be Africa, from where it was introduced to South America through the slave trade in the 16th century. Since the 17th century, several major epidemics of the disease have been recorded in the Americas, Africa, and Europe. In the 19th century, yellow fever was deemed one of the most dangerous infectious diseases.

Yellow fever presents in most cases in humans with fever, chills, anorexia, nausea, muscle pain (with prominent backache) and headache, which generally subsides after several days. In some patients, a toxic phase follows, in which liver damage with jaundice (inspiring the name of the disease) can occur and lead to death. Because of the increased bleeding tendency (bleeding diathesis), yellow fever belongs to the group of hemorrhagic fevers. The WHO estimates that yellow fever causes 200,000 illnesses and 30,000 deaths every year in unvaccinated populations; today nearly 90% of the infections occur in Africa.

A safe and effective vaccine against yellow fever has existed since the middle of the 20th century, and some countries require vaccinations for travelers. Since no therapy is known, vaccination programs are of great importance in affected areas, along with measures to prevent bites and reduce the population of the transmitting mosquito. Since the 1980s, the number of cases of yellow fever has been increasing, making it a re-emerging disease. This is likely due to warfare and social disruption in several African nations.