West Nile Virus IgG

This test is designed to detect IgG antibodies against the West Nile Virus (WNV) in the blood. A positive result typically indicates a past infection with the virus. It helps assess whether a person has previously been exposed to WNV and has developed long-term immunity.

Doctors may order this test if a person has symptoms consistent with West Nile fever or neuroinvasive disease, such as fever, headache, stiff neck, or encephalitis-like symptoms, especially if they reside in or have recently traveled to an endemic area.

A blood sample is drawn from a vein and tested using enzyme-linked immunosorbent assay (ELISA) or other serologic methods to detect the presence of IgG antibodies.

A positive IgG result suggests a previous infection, while a negative result implies that there has been no prior exposure. It may be used alongside IgM testing to distinguish between recent and past infections.

If WNV IgG is positive but IgM is negative, it usually indicates prior infection. If symptoms persist or worsen, additional testing such as CSF analysis or PCR may be required. Management is mainly supportive, as there are no specific antivirals for WNV.