West Nile Virus
Basic Information
Definition
West Nile virus is transmitted by the bite of infected mosquitoes. Most people who become infected have mild or no symptoms, but a few develop encephalitis, meningitis, or polio-like paralysis.
Epidemiology & Demographics
• Most infections are asymptomatic; 1 in 5 patients develop fever, and 1 in 150 patients develop central nervous system disease.
• West Nile virus is found in Africa, Europe, the Middle East, Asia, Australia, and since 1999, in the Americas.
Clinical Presentation
• Febrile illness: fever, fatigue, myalgias, headache, back pain, pharyngitis, nausea, vomiting, diarrhea, abdominal pain, and maculopapular rash
• Central nervous system (CNS) disease (i.e., encephalitis, meningitis, or meningoencephalitis): fever, acute flaccid paralysis, meningismus, stupor, coma, seizures, nausea, vomiting, headache, myoclonus, and cranial nerve abnormalities
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