West Nile virus IgG (CLIA)

West Nile virus (WNV) is an arbovirus belonging to the family Flaviviridae and transmitted by mosquitoes of the genus Culex. WNV outbreaks are frequent in North America, Europe and Middle East. WNV cases have been reported from all around the world. WNV infection is usually mild and self-limiting. It is calculated that 80% of those infected with WNV are asymptomatic. When symptomatic, and after an incubation period of 2–15 days, there can be fever, fatigue, headache, malaise, muscle pain, nausea, vomiting, lymphadenopathy and a transient rash. Neuroinvasive disease (meningitis, encephalitis, or acute flaccid paralysis) develops in <1% of infected persons. Direct detection of the virus from serum or cerebrospinal fluid can be carried out by molecular techniques or cell culture. Viremia is only present for a brief period of time (up to 7 days). Serology constitutes the mainstay of WNV diagnosis. The mean time from the detection of viral RNA to IgM has been reported as 4 days, and to IgG detection as 8 days. If serum is collected within 8 days of illness onset, the absence of detectable virus-specific IgM does not rule out the diagnosis of WNV infection. In neuroinvasive WNV disease specific IgM is almost always detectable by the time when the symptoms appear. Detectable IgM can persist up to one year.