What virus causes yellow fever?

From the Guidelines

Yellow fever is caused by the yellow fever virus (YFV), a mosquito-borne flavivirus. This virus is primarily transmitted to humans through the bite of infected mosquitoes, mainly Aedes and Haemagogus species 1. The virus gets its name from the jaundice (yellowing of skin and eyes) that occurs in some infected individuals due to liver damage.

Key Characteristics of Yellow Fever Virus

• YFV is a ribonucleic acid (RNA) virus that belongs to the genus Flavivirus 1
• It is related antigenically to West Nile virus, St. Louis encephalitis virus, and Japanese encephalitis virus
• YFV has three transmission cycles: jungle (sylvatic), intermediate (savannah), and urban 1

Transmission and Disease

• The virus is transmitted via mosquitoes from monkey to human when the humans encroach into the jungle during occupational or recreational activities 1
• In Africa, an intermediate (savannah) cycle exists that involves transmission of the YFV from tree-hole–breeding Aedes spp. to humans living or working in jungle border areas 1
• Humans infected with YFV experience the highest levels of viremia and are infectious to mosquitoes shortly before the onset of fever and for 3–5 days thereafter 1

Prevention and Treatment

• Protection against yellow fever is available through vaccination with the live-attenuated 17D vaccine strain, which provides immunity for at least 10 years and is recommended for travelers to endemic regions in Africa and South America 1
• Vaccination is the most effective way to prevent yellow fever, and it is crucial for reducing the risk of morbidity and mortality associated with the disease.

From the Research

Virus Classification

• The yellow fever virus is classified as a Flavivirus, which is a genus of viruses in the family Flaviviridae 2, 3, 4.
• Flaviviruses are small, enveloped, positive-sense, single-strand RNA viruses 4.

Transmission and Endemic Areas

• Yellow fever is transmitted by Haemagogus, Sabethes, or Aedes aegypti mosquitoes 2.
• The disease is endemic in forest areas in Africa and Latin America, with a reservoir of the disease in monkeys 2, 3, 4.
• There are two forms of yellow fever: sylvatic (transmitted accidentally when approaching forests) and urban (perpetuated by Aedes aegypti) 2.

Disease Characteristics

• Yellow fever has an incubation period of 3 to 6 days and sudden onset of symptoms, including high fever, myalgia, headache, nausea/vomiting, and increased transaminases 2, 3.
• The disease can range from asymptomatic to severe forms, with the most serious forms occurring in around 15% of those infected and resulting in high lethality rates 2, 3, 4.
• Severe forms of the disease can lead to renal, hepatic, and neurological impairment, as well as bleeding episodes 2, 3, 4.