How do humans become infected with yellow fever virus?
Yellow fever is transmitted to humans by the bite of infected mosquitoes from, principally, Aedes and Haemagogus mosquito species. The disease occurs in two forms – urban and sylvatic (jungle) yellow fever. Both forms are caused by the same virus. In tropical rainforests, yellow fever occurs in monkeys that are infected by mosquitoes. The yellow fever virus is passed onto other mosquitoes that feed on infected monkeys. These infected mosquitoes bite humans that enter the forest, resulting in some cases of yellow fever. This form of the disease is known as ‘sylvatic’ or ‘jungle’ yellow fever. In some parts of Africa mosquitoes that breed around households, can infect humans. Urban yellow fever happens when infected people introduce the virus into areas with high human populations. Mosquitoes carry the virus from person to person.
