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Tests and diagnosis
By Mayo Clinic staffYour 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.
References
- West Nile virus: Questions and answers. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/qa/symptoms.htm. Accessed Sept. 5, 2012.
- West Nile virus: Fact sheet. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/wnv_factSheet.htm. Accessed Sept. 5, 2012.
- Petersen LR. Clinical manifestations and diagnosis of West Nile virus infection. http://www.uptodate.com/ index. Accessed Sept. 5, 2012.
- Ferri FF. Ferri's Clinical Advisor 2013: 5 Books in 1. Philadelphia, Pa.: Mosby Elsevier; 2012. http://www.mdconsult.com/books/about.do?eid=4-u1.0-B978-0-323-08373-7..00002-9&isbn=978-0-323-08373-7&about=true&uniqId=343863096-23. Accessed Sept. 6, 2012.
- West Nile virus. National Institute of Allergy and Infectious Diseases. http://www.niaid.nih.gov/topics/westnile/understanding/pages/what.aspx. Sept. 6, 2012.
- Centers for Disease Control and Prevention, et al. West Nile virus and other arborviral diseases — United States, 2011. MMWR. 2012;61:510. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6127a3.htm?s_cid=mm6127a3_w. Accessed Sept. 5, 2012.
- Petersen LR. Treatment and prevention of West Nile virus infection. http://www.uptodate.com/ index. Accessed Sept. 5, 2012.
- Updated information regarding insect repellants. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/RepellentUpdates.htm. Accessed Sept. 7, 2012.
- Anderson CF (expert opinion). Mayo Clinic, Rochester, Minn. Sept. 10, 2012.
- Mahoney KR (expert opinion). Food and Drug Administration, Rockville, Md. Jan. 10, 2011.
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