Viral IgG Antibody to West Nile Virus (Serum/Plasma)

What This Test Measures

West Nile virus is a mosquito-borne illness that can affect the nervous system. After you recover from an infection, your immune system creates antibodies to protect you from getting sick again. This test looks for IgG antibodies, which develop several weeks after infection and can remain in your blood for months or years.

Why It’s Done

Doctors may order this test if you’ve had symptoms like fever, headache, body aches, or neurological issues (such as confusion, weakness, or seizures) that could suggest West Nile virus infection. It’s also used in outbreaks or during travel to high-risk areas to check for past exposure.

How the Test Works

A small blood sample is taken from your arm and sent to a lab. The lab uses an immunoassay (a sensitive test that detects specific antibodies) to measure IgG levels in your serum or plasma. This process helps confirm whether your body has encountered the West Nile virus.

What to Expect Before the Test

There’s little to prepare for this test. You may have a slight bruise or pinch at the injection site, but it usually doesn’t cause discomfort. If you’re on blood-thinning medication, let your doctor know before the test.