yellow fever an acute infectious type of
hemorrhagic fever, transmitted by the female of certain species of mosquitoes, and characterized by fever, jaundice due to necrosis of the liver, and albuminuria. It is less rampant today than previously, largely because of vaccination and better control of the mosquitoes, but it is still a danger in most tropical countries. Among native inhabitants who contract the disease there is a mortality rate of about 5 per cent. In visitors from other climates, fatalities once ran as high as 40 per cent but are now much lower. With proper immunization precautions, a visitor from a temperate country today takes only a minimal risk.
The mosquito that transmits classic yellow fever is
Aedes aegypti. In the jungles of Brazil and in parts of Africa, in the absence of
Aedes aegypti, the disease may be carried by a different mosquito species that lives in treetops. These forest mosquitoes can communicate the disease to forest workers and also to certain animals, such as monkeys and marmosets, which then serve as virus reservoirs and as sources of reinfection for humans. This form of the disease is called
jungle or
sylvan yellow fever, and it is difficult to control because of the virtual impossibility of eradicating the tree-inhabiting mosquitoes.
Symptoms and Treatment. Yellow fever has an incubation period of 3 to 6 days. It then manifests suddenly and intensely with fever, headache, muscular aches, and prostration. A few days later, the temperature suddenly falls, only to rise again. The pulse is originally very rapid, but then slows gradually to less than 50 beats per minute. In addition to the characteristic yellowing of the skin, the urine becomes darker. There may be frequent vomiting, and blood may become noticeable in the vomitus (so-called “black vomit”). There may also be bleeding from the mucous membranes.
The disease runs its course in a little more than a week. Those who survive suffer no permanent damage. The jaundice completely disappears. Furthermore, these persons are immune from a second attack. In fatal cases, death is usually due to liver, myocardial, or kidney failure.
There is no specific drug for the cure of yellow fever. The effects of the disease can be mitigated by analgesics, sedatives, bed rest, and a high-calorie, high-carbohydrate diet.
Patient Care. The patient's fever is controlled with cold or tepid sponges and other measures to lower body temperature (see
fever). The diet consists of liquids and easily digested foods until the vomiting stops, and then is gradually increased. The patient's bed and room should be well screened to prevent transmission of the fever to others via mosquitoes.