Encephalitis, West Nile Virus

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

• 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

Treatment

• Supportive