Disease Information for Yellow fever: Definition

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  • incubation 3-6 days;An acute infectious disease primarily of the tropics, caused by a virus and transmitted to man by mosquitoes of the genera Aedes and Haemagogus; major hemorrhage and liver involvement; moderate renal and absent encephalitis;--------------------. Endemic area exposure (tropical South and Central America, Africa, but not Asia); Sudden onset of severe headache, aching in legs, and tachycardia; Brief (1 day) remission, followed by bradycardia, hypotension, jaundice, hemorrhagic tendency; Proteinuria, leukopenia, bilirubinemia, bilirubinuria; Yellow fever is a zoonotic flavivirus infection transmitted by Aedes and jungle mosquitoes; It occurs in an urban and jungle cycle in Africa and in a jungle cycle in South America; Epidemics have extended far into the temperate zone during warm seasons; The role of yellow fever in preventing economic development in tropical areas is devastating; The mosquito transmits the infection by first biting an individual having the disease and then biting a susceptible individual after the virus has multiplied within the mosquito"s body; The incubation period in humans is 3–6 days; Adults and children are equally susceptible, though attack rates are highest among adult males because of their work habits; Mild form: Symptoms are malaise, headache, fever, retro-orbital pain, nausea, vomiting, and photophobia; Bradycardia may be present; Severe form: About 15% of those infected with yellow fever develop severe illness; Initial symptoms are similar to the mild form, but a brief remission after about 3-6 days of acute illness is followed by a "period of intoxication" manifested by fever and bradycardia (Faget"s sign), hypotension, jaundice, hemorrhage (gastrointestinal, nasal, oral), and delirium that may progress to coma;Leukopenia occurs, although it may not be present at the onset; Proteinuria is present, sometimes as high as 5–6 g/L, and disappears completely with recovery;Abnormal liver function tests are seen, and prothrombin time may be elevated; Serologic diagnosis is chiefly by measurement of IgM by a capture ELISA; Other serologic tests include hemagglutination-inhibition and neutralization; PCR protocols are becoming more widely available;It may be difficult to distinguish yellow fever from hepatitis, malaria, leptospirosis, louse-borne relapsing fever, dengue, and other hemorrhagic fevers on clinical evidence alone; Serologic confirmation is often needed; Transmission is prevented through mosquito control; Live virus vaccine is highly effective and should be provided for immunocompetent persons over 9 months of age living in or traveling to endemic areas;

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