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Yellow fever, a mosquito-borne viral disease, is not normally found in the U.S. It typically appears in travelers to other countries where the disease is more prevalent, such as sub-Saharan Africa and tropical South America. It is maintained in nature as mosquitoes pass the disease among themselves, to monkeys, then back again. Humans may also serve as hosts for the disease.
- What it is: Yellow fever is a viral disease, carried by mosquitoes.
Transmission: Yellow fever is transmitted by mosquitoes. Both humans and monkeys may be affected.
Symptoms: Some infections have no symptoms at all. When symptoms are present, they appear three to six days after infection.
There are two disease phases of Yellow Fever. The first phase, called the acute phase, is normally characterized by fever, muscle pain, backache, headache, shivers, loss of appetite, nausea and vomiting. In many cases, the high fever is accompanied by a slow pulse. This phase lasts three to four days, after which symptoms usually disappear for most patients.About 15% of patients, however, enter the second, or toxic phase 24 hours after the first. Fever returns, and jaundice develops, causing the skin to appear yellow. Abdominal pain accompanied by vomiting can occur, as well as bleeding from the mouth, nose, eyes and stomach. Once this happens, blood may appear in the vomit and feces, and kidney function will deteriorate. The patient may become delirious. Half of second-phase patients die within two weeks. The other half recover without significant lasting effects.
Prevention: There is a safe and highly effective vaccine available. Children under the age of six months and pregnant women should not, under normal circumstances, receive the vaccine.
Travelers should be vaccinated before traveling to at-risk regions, which include 33 countries in Africa, several Caribbean islands, and nine South American countries. Bolivia, Brazil, Columbia, Ecuador and Peru are considered at greatest risk.In addition to vaccination, travelers to endemic areas should also take precautions against mosquitoes.
Treatment: There is no specific treatment for yellow fever. Special care should be taken to ward off and treat dehydration in patients. Any resulting bacterial infections should be treated with antibiotics.