Yellow fever is a virus disease carried by certain mosquitoes. The virus damages many body tissues, but especially the liver. As a result of this damage, the liver cannot function properly and yellow bile pigments gather in the skin. These pigments make the skin look yellow and give the disease its name.
In most cases, the Aedes aegypti mosquito carries the yellow fever virus from one person to another. Some monkeys and sloths may also be infected. When the mosquito bites an infected person or animal, the virus enters the insect's body, where it develops rapidly. After 9 to 12 days, the bite of the mosquito can produce yellow fever. A mosquito that becomes infected with the virus can transmit the disease for the rest of its life.
Symptoms. The first stage of yellow fever begins from three to six days after a person has been bitten. The victim develops a fever, headache, and dizziness, and the muscles ache. In many people, the disease progresses no further. But in others, the fever drops for a day or two and then rises steeply. The skin turns yellow and the patient's gums and stomach lining bleed.
Many patients recover from this stage. But some become delirious and go into a coma. Death follows the coma in most cases. Only from 2 to 5 per cent of all cases of yellow fever result in death, though the figure may be higher during an epidemic. Patients who recover have lifelong immunity to the disease.
Prevention. Yellow fever was once widespread throughout Central America, parts of South America, Africa, and some tropical islands. Occasional outbreaks of the disease continue to occur in jungle areas, especially in South America. However, yellow fever is under control in most urban areas. A United States Army physician, William Gorgas, developed mosquito control measures that eliminated the disease as a major health menace in the Panama Canal Zone. The disease can also be prevented with a vaccine developed in 1937 by Max Theiler, a South African research physician.
The conquest of yellow fever was one of the great achievements of modern medicine. In 1881, Carlos Finlay, a Cuban physician, suggested that a mosquito transmitted the disease. Walter Reed, a U.S. Army doctor, proved that yellow fever was carried by a mosquito. Reed suggested that the cause was a microorganism. In 1927, three research physicians proved that the microorganism was a virus.