West Nile Virus (WNV) Antibody Serum Test

West Nile virus (WNV) is most commonly transmitted to humans by mosquitoes. You can reduce your risk of being infected with WNV by using insect repellent and wearing protective clothing to prevent mosquito bites. There are no medications to treat or vaccines to prevent WNV infection. Fortunately, most people infected with WNV will have no symptoms. About 1 in 5 people who are infected will develop a fever with other symptoms. Less than 1% of infected people develop a serious, sometimes fatal, neurologic illness.

No symptoms in most people. Most people (70-80%) who become infected with West Nile virus do not develop any symptoms.

Some signs and symptoms of WNV include:

• Headache
• Fever, chills
• Nausea, vomiting
• Muscular weakness
• Skin rash on the back or chest

Signs and symptoms associated with more severe WNV that has central nervous system involvement may include:

• High fever
• Extreme muscle weakness
• Neck stiffness
• Stupor, disorientation
• Tremors, convulsions
• Coma
• Paralysis (rarely)

Who is at risk for infection with West Nile virus?

Anyone living in an area where West Nile virus is present in mosquitoes can get infected. West Nile virus has been detected in all lower 48 states (not in Hawaii or Alaska). Outbreaks have been occurring every summer since 1999. The risk of infection is highest for people who work outside or participate in outdoor activities because of greater exposure to mosquitoes.

Antibody testing is primarily used to help diagnose a current or recent infection. There are two classes of WNV antibodies produced in response to infection: IgM and IgG

IgM antibodies are typically detectable 2 weeks after exposure and will fall below detectable levels after several months.
IgG antibodies are typically detectable 3-4 weeks after exposure and persist after a person has recovered.