Molecular Test Used to Battle West Nile Virus

The West Nile Virus (WNV) laboratory test is performed when a person who may have had recent exposure to the virus shows possible signs and symptoms of an infection.

The test is able to confirm whether the infection exists, allowing physicians to take action to control its impact and in severe cases, this might include hospital care where patients can receive supportive treatment including intravenous fluids, help with breathing, and nursing care.

Laboratory diagnosis of WNV infections is generally accomplished by testing of serum or cerebrospinal fluid (CSF) to detect virus-specific IgM and neutralizing antibodies. There are four WNV IgM ELISA kits from different manufacturers that are commercially available in the USA and are approved by US Food and Drug Administration (FDA; Silver Springs, MD, USA). In serious or fatal cases, the nucleic acid amplification test (NAAT), histopathology with immunohistochemistry and virus culture of autopsy tissues can also be useful. Only a few state laboratories or other specialized laboratories are capable of doing this specialized testing.

The NAAT technique is used because it measures the WNV’s genetic material, the test can detect an infection before the antibody test. This test is routinely used to screen donated units of blood, as well as donated tissue and organs. It also can be used to test birds and mosquito pools for WNV, often before any people have been identified with the disease, which helps public health experts track the virus’s spread through the community or region. Severe symptoms of WNV can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, and paralysis.

A record-breaking 1,590 human cases of WNV have been reported in the USA during 2012, including 65 deaths, according to the US Centers for Disease Control and Prevention (CDC; Atlanta GA, USA). Alan Mertz, MA, the president of the American Clinical Laboratory Association (Washington, DC, USA), said, "The test was developed quickly to respond to WNV when it first appeared in the USA. The test is a good example of the kind of innovative tests that clinical laboratories have discovered quickly in response to new and emerging medical crises, such as human immunodeficiency virus (HIV), herpes meningitis, severe acute respiratory syndrome (SARS), Influenza A subtype H1N1, and Avian flu.”

Related Links:

US Food and Drug Administration

US Centers for Disease Control and Prevention

American Clinical Laboratory Association