Viral infection prevalent in Central and South America and Africa, which occurs in Western Europe in travellers from these areas. The virus multiplies in the Aedes mosquito, and for the rest of its life span the insect can transmit the virus to man. There are two kinds of yellow fever, the urban variety, in which human beings carry the virus, and the jungle type in which a mosquito transmits the virus to man from infected monkeys.
The virus causes damage to the liver and the kidneys and the onset of the disease is marked by high fever (40°C), severe headaches, back and muscular pain. The mucous membranes of the mouth, nose and throat swell and become painful; the patient complains of pains in the stomach, nausea and vomiting. Jaundice sets in after a few days, with slight skin, stomach and intestinal bleeding, and the kidneys are also affected. In mild cases the condition begins to improve after a few days, in serious ones a second period of fever begins, after an initial improvement. At this stage organ failure and death are not uncommon.