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West Nile Virus Testing

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Also known as: WNV Tests; WNV by NAAT
Formal name: West Nile Virus, IgM and IgG Antibodies and Nucleic Acid Amplification Tests

The Test Sample

What is being tested?

West Nile virus (WNV) is an infection that is transmitted to humans primarily by mosquitoes that have bitten infected birds or other infected humans. Testing detects either the West Nile virus directly or antibodies produced in response to WNV infection in blood and/or cerebrospinal fluid (CSF).

The virus is not passed through handling or consumption of infected birds or directly from person-to-person; however, there have been rare cases of WNV being transmitted to others through blood donations, organ transplants, and from a mother to child during pregnancy, delivery, or through breast milk.

About 80% of people infected with WNV experience no symptoms. In the other 20%, it causes flu-like symptoms such as headache, fever, nausea, muscular weakness, and/or a skin rash on the back or chest. These symptoms usually resolve without treatment within a few days to a few weeks. Only about 1 in 150 people infected with WNV becomes seriously ill with an infection that affects the central nervous system. These people may experience severe symptoms such as confusion, convulsions, high fever, neck stiffness, headaches, or a coma. They may have encephalitis and/or meningitis and/or may experience muscular paralysis. This serious form of WNV is much more common in the elderly, people with weakened immune systems (immunocompromised), and individuals with underlying conditions such as diabetes or high blood pressure (hypertension). While most symptoms resolve within several weeks, some nerve damage and paralysis may linger or be permanent.

The two types of WNV testing include:

  • Antibody testing—detects either IgM or IgG class of WNV antibodies
  • Nucleic acid amplification (NAAT)—detects the genetic material (RNA) of WNV

How is the sample collected for testing?

Cerebrospinal fluid is collected from a spinal tap and/or a blood sample is drawn from a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.