Yellow fever is a viral infection that is present in some tropical areas of Africa and the central area of South America, where it has caused large outbreaks in the past.
The virus is transmitted by mosquitoes which also act as an important reservoir. Monkeys and humans also act as reservoirs in the jungle yellow fever and the urban yellow fever cycles.
Following the insect bite, most infections remain without symptoms. In clinical cases, symptomatic infection appears after an incubation period of 3–6 days. First symptoms are high fever and red eyes, then after a quiet period, a second rise in temperature, accompanied by signs of liver and kidney failure and bleedings (primarily intestinal). Up to 50% of cases with liver damage may die. No specific therapy is available.
A highly effective vaccine is available, providing immunity to 95% of vaccinated persons that should be recommended to travellers to endemic areas.