INTRODUCTION — Yellow fever is viral hemorrhagic fever with a high death rate, that is transmitted by mosquito bites. Clinical manifestations include liver failure, kidney failure, clotting disorder and shock. There are seven major types. Humans and certain monkey species are extremely susceptible to infection.
Some primate species develop fatal infection with features similar to the disease in humans.
Yellow fever occurs in tropical regions of sub-Saharan Africa and South America; it is an endemic and epidemic disease problem of considerable magnitude.
Mosquito-borne epidemics in Africa occur where large human populations reside in high density and immunization coverage is low. Human-to-human transmission in the absence of the mosquito does not occur.
Fewer cases occur in South America as vaccination coverage is relatively high (80 to 90 percent in endemic areas of South America).
In both Africa and South America only a small proportion of cases are officially recorded because the disease often occurs in remote areas, recognition of outbreaks is delayed, and diagnostic facilities are limited.
Transmission cycles — The primary transmission cycle involves monkeys and daytime biting mosquitoes (Aedes species in Africa; Haemagogus and Aedes species in South America).
In recent years, the Aedes mosquito has reinvaded areas of South America where it had previously been eradicated, increasing the risk that urban yellow fever may reemerge.
Outcome — The outcome is determined during the second week after onset, at which point the patient either dies or rapidly recovers.
Convalescence may be associated with fatigue lasting for several weeks.
DIAGNOSIS is made by Careful History and Physical Examination in addition to;
Serologic diagnosis is best accomplished using (ELISA) for IgM. Cross-reactions with other flaviviruses complicate the diagnosis of yellow fever by serologic methods, particularly in Africa where multiple flaviviruses circulate.
Rapid diagnostic tests — In general these are not widely available and are reserved for special studies.
Virus isolation — Virus isolation after culture of virus in suckling mice, mosquitoes, or mammalian cell cultures.
TREATMENT — The treatment of yellow fever consists of supportive care; there is no specific antiviral therapy available. Management of patients may be improved by modern intensive care, but this is generally not available in remote areas where yellow fever often occurs. Travelers hospitalized after return to the United States or Europe have had fatal outcomes in spite of intensive care, demonstrating the inexorable course of severe yellow fever.
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