English subtitles for clip: File:En.Video-Yellow fever.webm

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Yellow fever is a viral disease of typically short duration.[1]The disease is caused by yellow fever virus and is spread by the bite of an infected female mosquito.[1]In 2013, yellow fever resulted in about 127,000 severe infections and 45,000 deaths.[1]



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Yellow fever begins after an incubation period of three to six days.[2] Most cases only cause a mild infection with fever, headache, chills, back pain, fatigue, loss of appetite, muscle pain, nausea, and vomiting.[3] In 15 percent of cases, though, people enter a second, toxic phase of the disease with recurring fever, this time accompanied by jaundice due to liver damage, as well as abdominal pain.[4]



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Yellow fever is caused by yellow fever virus, an enveloped RNA virus 40 to 50 nanometers in width, it is of the family Flaviviridae.[5]The positive-sense, single-stranded RNA is around 11,000 nucleotides long and has a single open reading frame encoding a polyprotein. Host proteases cut this polyprotein into three structural proteins, C, prM, E, and seven nonstructural proteins NS1, NS2A, NS2B, NS3, NS4A, NS4B, NS5; the enumeration corresponds to the arrangement of the protein coding genes in the genome.[6]



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Yellow fever virus is mainly transmitted through the bite of the yellow fever mosquito Aedes aegypti, but other mostly Aedes mosquitoes such as the tiger mosquito, Aedes albopictus can also serve as a vector for this virus. Like other arboviruses, which are transmitted by mosquitoes, yellow fever virus is taken up by a female mosquito when it ingests the blood of an infected human or another primate.[7]



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After transmission from a mosquito, the viruses replicate in the lymph nodes and infect dendritic cells in particular. From there, they reach the liver and infect hepatocytes, probably indirectly via Kupffer cells, which leads to eosinophilic degradation of these cells and to the release of cytokines. Apoptotic masses known as Councilman bodies appear in the cytoplasm of hepatocytes.[8][9]



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Yellow fever is most frequently a clinical diagnosis, based on symptomatology and travel history. Mild cases of the disease can only be confirmed virologically.[10][11]A direct confirmation can be obtained by reverse transcription polymerase chain reaction, where the genome of the virus is amplified.[12]



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Vaccination is recommended for those traveling to affected areas, because non-native people tend to develop more severe illness when infected. Protection begins by the tenth day after vaccine administration in 95 percent of people,[13] and had been reported to last for at least 10 years. The World Health Organization,  however, states that a single dose of vaccine is sufficient to confer lifelong immunity against yellow fever disease.[14]



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As with other Flavivirus infections, no cure is known for yellow fever. Hospitalization is advisable and intensive care may be necessary because of rapid deterioration in some cases.[15]Symptomatic treatment includes rehydration and pain relief with drugs such as paracetamol.[16]



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Yellow fever is common in tropical and subtropical areas of South America and Africa. Worldwide, about 600 million people live in endemic areas. The WHO estimates that 200,000 cases of disease and 30,000 deaths a year occur, but the number of officially reported cases is far lower.[17][18]



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An estimated 90 percent of yellow fever infections occur on the African continent.[12] In 2016, a large outbreak originated in Angola that tallied thousands of confirmed and suspected cases,[19] and spread to neighboring countries before being contained by a massive vaccination campaign.[20][21]



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Carlos Finlay, a Cuban doctor and scientist, proposed in 1881 that yellow fever might be transmitted by mosquitoes rather than direct human contact.[22][23] Since the losses from yellow fever in the Spanish–American War around 1890 were extremely high, Army doctors began research experiments with a team led by Walter Reed, and others. They successfully proved Finlays mosquito hypothesis. Yellow fever was the first virus shown to be transmitted by mosquitoes.[24]