West Nile Virus Serology (IgM), Serum - RRPL
Discipline
Microbiology
Overview
Description
- West Nile Virus (WNV) is transmitted to humans by the Culex species of mosquitos in Canada
- Most WNV infections are asymptomatic. Some may have mild symptoms including fever, headache, body aches, a mild rash, and/or swollen lymph nodes. In rare cases, WNV can cause encephalitis or meningitis
Ordering Recommendations
- Symptomatic patients
Specimen Information
Specimen types accepted
- Serum
Specimen collection container
- Serum separator tubes (SST; Tiger top or Gold top)
Collection procedure
- Collect blood in serum separator tube (SST). Serum must be separated from whole blood by centrifugation within 24h of collection.
Required volume
- 1 SST (tiger or gold Top) tube, 2 mL minimum
Transport and stability
- Serum must be separated from whole blood within 24h of collection. Serum may be shipped at ambient temperature.
Testing Information
Relevant clinical history
- WNV IgM results must be interpreted in conjunction with patient symptoms and exposure as WNV IgM antibodies may persist for a year or more.
Clinical interpretation
- This should be the initial test for diagnosis of suspect West Nile Virus
Performance
Methodology
- Qualitative IgM immunoassay from Focus Diagnostics (Negative, Indeterminate, or Positive)
Days/times performed
- All specimens will be tested at RRPL
- Indeterminate or Positive specimens will be forwarded to the National Microbiology Laboratory (NML) for further testing.
Maximum laboratory time
- Turnaround time of 3 days from receipt at RRPL
- Further testing at the NML may take up to 4 weeks
Specimen retention time
- Serum is retained for 10 days after completion of testing
Other information
-
All Indeterminate or Positive specimens are forwarded to the National Microbiology Lab (NML) for further testing
-
Positive results are reported to a Medical Health Officer
Last Updated: July 28, 2025