Saint Louis encephalitis virus

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Background

  • Single-stranded positive-sense enveloped virus in the family Flaviviridae and genus Flavivirus
  • Reservoir is birds
  • Vector-borne, transmitted by Culex mosquitoes
  • Outbreaks have occurred in the US, Canada, and Mexico, with sporadic cases in Central and South America

Clinical Manifestations

  • Incubation period 4 to 21 days
  • Risk of encephalitis is highest in older age >60 years
  • Presents with non-specific febrile illness with severe headache and meningismus, followed by focal neurological deficits including brainstem, cerebellum, and cranial nerves
  • Tremors of the eyelids, tongue, lips, and extremities
  • Seizures are uncommon
  • Usually no motor or sensory deficits, but may develop urinary symptoms

Prognosis and Complications

  • Mortality 5-15%, but higher in the elderly
  • Up to half of survivors have neuropsychiatric symptoms persisting at 3 years

Diagnosis

  • Serology demonstrating IgM in CSF or serum

Management

  • Supportive