Microcheck 284

Infectious mononucleosis occurs worldwide and is transmitted from person to person by saliva. Curiously, the causative virus is associated with different malignancies, but only in certain geographic areas or in AIDS patients. Yellow fever virus infects

Table 28.7 Yellow Fever

Symptoms

Often only headache and fever. Severe cases characterized by high fever, jaundice, black vomit, and hemorrhages into the skin

Incubation period

Usually 3 to 6 days

Causative agent

Yellow fever virus, an enveloped, single-stranded RNA virus of the flavivirus family

Pathogenesis

Virus multiplies locally at site of introduction by an infected mosquito; spreads to the liver and throughout the body by the bloodstream.Virus destroys liver cells, causing jaundice and decreased production of blood-clotting proteins. Hemorrhages and decreased strength of the heart result in circulatory failure and kidney failure

Epidemiology

Virus persists in forest primates and the mosquitoes that feed on them, in Africa and Central and South America; human epidemics occur when the virus infects household mosquitoes that feed on humans

Prevention and treatment

There is a highly effective attenuated viral vaccine. No proven antiviral therapy is available

monkeys that live in tropical forests of Africa and South and Central America, and the mosquitoes that bite them. Transmission of the virus among human beings can occur wherever there is a human-biting mosquito species that is susceptible to the virus.

■ What characteristic changes occur in the blood of patients with infectious mononucleosis?

■ What is the name of the tumor from which EB virus was first isolated?

■ Why does it take more than a week before a mosquito just infected with yellow fever virus can transmit the disease?

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