Antibody to West Nile Virus, IgM (Serum/Plasma)
This test detects antibodies in your blood that your immune system produces in response to the West Nile virus. It helps determine if you’ve been exposed to the virus.
["IgM antibodies can indicate recent West Nile virus infection."]
Key facts at a glance
- LOINC
- 75404-4
- Short code
- WNV Ab Ser Ql HAI
- Synonyms
- WNV Ab Ser Ql HAI
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 1.5
- Ref high
- 9
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- hai
- CPT
- 83002
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What This Test Measures
The test looks for IgM antibodies, a type of immune protein your body makes shortly after infection. These antibodies appear within days to weeks after exposure and can help confirm if you’ve been infected with West Nile virus.
Why It’s Done
Your healthcare provider may order this test if you’ve had symptoms like fever, headache, body aches, or neurological issues (such as weakness, confusion, or seizures) that could be linked to West Nile virus. It’s also used in outbreaks or after contact with infected mosquitoes.
How It Works
A small blood sample is taken, usually from your arm. The serum or plasma is then tested in a lab to detect IgM antibodies using an immunoassay method, which identifies the presence of these antibodies based on their reaction with virus-specific markers.
What to Expect Before the Test
No special preparation is needed, but inform your provider if you’re on blood-thinning medications or have bleeding disorders, as this may affect blood collection.
Reference range
Follicular: 1.5-9.0 mIU/mLN/A
For females: inform if menstrual cycle status. For certain tests, timing within menstrual cycle may matter.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Positive IgM results suggest recent West Nile virus infection. While IgM antibodies fade over time, they remain detectable for weeks to months. If you test positive, follow-up testing (like IgG antibody testing) may be needed to confirm the diagnosis and assess severity. Always consult your healthcare provider for interpretation, as other infections or conditions can sometimes produce similar antibody responses.
Short name
IgM Antibody to West Nile Virus
Frequently asked questions
How soon after exposure can I expect results?
Can I get this test at home?
What if my test is positive but I don’t remember symptoms?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy