Yellow Fever

Yellow Fever, noncontagious, infectious disease, caused by a virus, and characterized in severe cases by high fever and jaundice. Originally yellow fever was believed to be exclusively a disease of humans, but research has revealed that it also affects monkeys and other animals. It is believed that diseased monkeys of Africa and tropical America are the primary source of infection and that carrier mosquitoes transmit the infection to humans. This type of the disease, which occurs only sporadically in human beings, is known as jungle yellow fever. If infected individuals move into a populated area, they may be bitten by a semidomestic species of mosquito, such as Aëdes aegypti, which lives close to human habitations. These feed on the blood of humans and are the chief transmitting agents in epidemics of urban yellow fever.