Expanded Molecular Testing on Patients with Suspected West Nile Virus Disease

Area of Science:

• Medical Diagnostics
• Virology
• Public Health

Background:

• Current West Nile virus (WNV) diagnostics rely on serologic testing, which has limitations including cross-reactivity and potential failure in early infection.
• Confirmatory testing for WNV can be complex and time-consuming.

Purpose of the Study:

• To evaluate if combining molecular (RT-PCR) and serologic (IgM antibody) testing improves WNV disease detection in acute serum samples.
• To assess the utility of RT-PCR for WNV diagnosis in early-stage illness.

Main Methods:

• Analyzed 380 serum specimens collected within 7 days of symptom onset from 2014-2015.
• Performed WNV IgM antibody and RT-PCR tests on samples collected ≤3 days post-onset.
• Conducted WNV IgM antibody testing on samples collected 4-7 days post-onset, with RT-PCR on positive IgM samples.

Main Results:

• In samples collected ≤3 days post-onset, 12% (19/158) showed WNV infection evidence (16 IgM only, 1 RNA only, 2 both).
• In samples collected 4-7 days post-onset, 9% (21/222) were IgM positive, with no detectable WNV RNA.
• Routine WNV RT-PCR on acute serum is unlikely to significantly increase case detection over IgM antibody testing alone.

Conclusions:

• The addition of WNV RT-PCR to IgM antibody testing does not substantially enhance the detection of WNV disease in acute serum samples.
• WNV IgM antibody testing remains a primary diagnostic tool for early-stage West Nile virus infections.