West Nile virus

Diagnosis

• Serology
  • Serum or CSF for IgM antibodies is the standard test; usually positive by 3 to 8 days, and persist for 2 to 3 months
    • If submitted CSF, must also submit serum
  • May cross-react with other flaviviruses
  • Can be seronegative if immunosuppressed (e.g. rituximab), therefore may need to do PCR
• PCR
  • RNA virus, therefore needs reverse transcriptase step (RT-PCR)
  • Can be done on serum, CSF, and tissue
• On MRI, may have a slight preference for thalamus