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Key Features

  • Epidemics occur in summer–fall

  • Most infected individuals are asymptomatic

  • West Nile Fever develops in 20% and is characterized by

    • Fever

    • Headache

    • Retro-orbital pain

    • Nausea, vomiting

    • Lymphadenopathy

    • Maculopapular rash (20–50%)

  • Meningitis or encephalitis develops is < 1% of infected patients, but 10% of these cases are fatal

Clinical Findings

  • Children usually manifest with West Nile fever; neuroinvasive disease, most likely limited to meningitis develops in < one-third

  • Neurologic manifestations are most often those found with other meningoencephalitides, but some distinguishing features include

    • Polio-like acute flaccid paralysis

    • Movement disorders (parkinsonism, tremor, and myoclonus)

    • Brainstem symptoms

    • Polyneuropathy

    • Optic neuritis

  • Muscle weakness, facial palsy, and hyporeflexia are common


  • Diagnosis is best made by detecting IgM antibody (enzyme immunoassay) to the virus in cerebrospinal fluid

  • Polymerase chain reaction is a specific diagnostic tool, but is less sensitive than antibody detection

  • Antibody rise in serum can also be used for diagnosis


  • Supportive

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