Tests and diagnosis

By Mayo Clinic Staff

Your doctor can confirm the presence of West Nile virus or a West Nile-related illness, such as meningitis or encephalitis, by performing one of the following tests:

  • Laboratory tests. If you're infected, a blood test may show a rising level of antibodies to the West Nile virus. Antibodies are immune system proteins that attack foreign substances, such as viruses. A positive ribonucleic acid (RNA) test for the West Nile virus also is an indicator that you have the virus.
  • Lumbar puncture (spinal tap). The most common way to diagnose meningitis is to analyze the cerebrospinal fluid surrounding your brain and spinal cord. A needle inserted between the lower vertebrae of your spine is used to extract a sample of fluid for laboratory analysis. The fluid sample may show an elevated white cell count — a signal that your immune system is fighting an infection — and antibodies to the West Nile virus.
  • Brain tests. In some cases, an electroencephalography (EEG) — a procedure that tests your brain's activity — or an MRI scan can help detect brain inflammation.
Dec. 18, 2012

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