Saturday, September 11, 2021

Viral haemorrhagic fever: Yellow fever

Yellow fever is a viral haemorrhagic fever which strikes an estimated 200 000 persons world-wide each year and causes an estimated 30 000 deaths.The yellow fever (YF) virus is a Flavivirus, which currently contains over 70 viruses, of which most are arthropod-borne, including the dengue viruses. The virus is transmitted by Haemagogus, Sabethes or Aedes aegypti mosquitoes.

Yellow fever outbreaks occur in both rural and urban settings. In urban settings, outbreaks are likely to be larger and are difficult to control.

Yellow fever was an unknown disease until the discovery of the Americas. It probably originated in Africa and was possibly introduced to the American continent by ships carrying slaves and the vector Aedes aegypti. The first epidemic was reported in the American continent, where it is possible to characterize with greater certainty the infection by yellow fever, occurred in the Yucat√°n peninsula in 1648.

There are three different epidemiological patterns of yellow fever virus transmission: the sylvatic or forest pattern; the Aedes aegypti-borne urban cycle; and an intermediate cycle that bridges these two patterns. The different epidemiological patterns of transmission lead to the same clinical disease.

The incubation period is from three to six days after a bite from an infected mosquito. The classic form of yellow fever is a severe systemic disease with a high case-fatality rate, characterized by fever, prostration, compromised liver, kidney, and cardiac function, hemorrhagic manifestations, and shock. The progression of the disease can include three clinically distinct stages: infection, remission, and intoxication.
Viral haemorrhagic fever: Yellow fever

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