Besides conducting a physical exam, 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.
- 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 measures your brain's activity — or an MRI scan can help detect brain inflammation.