Detection of West Nile Virus Infection in Viral Encephalitis Cases, China.

This study detected West Nile virus (WNV) infection in serum samples of patients clinically diagnosed with viral encephalitis in the Japanese encephalitis virus (JEV) endemic area (seven provinces) and JEV nonendemic area (Xinjiang province) in China from 2011 to 2012. In JEV endemic areas, there were 22 positive cases of WNV immunoglobulin M (IgM) antibody in serum specimens of 65 JEV patients (JEV IgM antibody positive) in the acute phase, whereas WNV IgM antibodies were not detected in serum specimens of 63 non-JEV patients (JEV IgM antibody negative). However, the titer of JEV-neutralizing antibody was four times higher than that of WNV-neutralizing antibody in WNV-IgM-positive serum specimens. Detection was also conducted in serum specimens collected from 12 patients clinically diagnosed as viral encephalitis in Xinjiang; five serum specimens were WNV IgM antibody positive, and there were fourfold differences in WNV-neutralizing antibody titers between convalescent and acute serum. Meanwhile JEV-neutralizing antibody titer was negative or significantly lower than that of WNV-neutralizing antibody in the same specimens. WNV IgM antibodies positive were detected in acute serum specimens of patients clinically diagnosed with JEV infection in JEV-endemic areas, but no WNV neutralization antibodies were detected fourfold greater than that of the corresponding JEV antibodies. Clinical cases of WNV infection were detected in patients clinically diagnosed with viral encephalitis in Xinjiang.