A method and device for detecting a West Nile Virus (WNV) infection including contacting a biological sample from a subject with an anti-IgM antibody and a recombinant WNV E polypeptide and detecting whether the polypeptide substantially binds to an antibody in the sample. The invention also includes a method and device for determining whether an animal is infected with West Nile Virus (WNV), or is either not infected or is vaccinated with a WNV vaccine.