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Sylvatic yellow fever

Sylvatic, or jungle, yellow fever occurs in tropical rainforests and is caused by an arbovirus of the family Flaviviridae. This infectious disease is passed onto humans by infected sylvatic mosquitoes, which get the virus by feeding on ill monkeys. Cases are usually sporadic with mostly young men working in the forests affected.

Sylvatic yellow fever is a form of the yellow fever, with other cycles being intermediate yellow fever and urban yellow fever. All these three cycles exist in Africa, but only sylvatic and urban yellow fever occur in South America. Several mosquito species of the genus Aedes are responsible for the spreading of sylvatic yellow fever in Africa while also several species of Haemagogus mosquitoes, including Hg.janthinomys, Hg. equinus, Hg. lucifer, Hg. leucocelaenus, Hg.spegazzinii, and Hg. capricornii are vectors of sylvatic yellow fever virus in South America.

Yellow fever is hardlyr ecognizable in its early stages and can be confused with malaria, dengue fever, viral hepatitis or other illnesses or even poisoning. Blood tests can detect yellow fever antibodies that are produced in response to the infection. There is no true cure for yellow fever, so it is very important to get vaccinated.

In many cases infection is relatively mild and can be difficult to differentiate from other fevers while in harder cases sharp onset of fever, chills and pain in the lover back start in 3-6 days and symptoms last for about 3-4 days. After these several days most patients improve and their symptoms disappear, or about 15% of patients enter a toxic phase. Usually the pulse slows and jaundice develops with hemorrhages in the digestive tract leading to black vomiting. Bleeding can occur from the mouth, nose, eyes or stomach. Different level of kidney function disorders can occur up to a complete kidney failure. Half of the patients in this phase die within one or two weeks and remaining recover without significant damage.

Originally sylvatic yellow fever comes from Western Africa where virus resides in the monkeys of the high jungle canopy. When Europeans began to colonize western Africa the virus killed hundreds of colonists. At the end of 19th century sylvatic yellow fever was spread to Americas and it ranged as far north as Boston and claimed up to 75,000 lives a year in the United States then.

Although mosquitoes can be controlled with insecticides or other measures and there is a vaccine against the yellow fever virus, but neither of those are complete in areas of risk and occasional outbreaks in Bolivia, Brazil, Colombia, Peru or other countries still happen.


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