Illustration of West Nile virus (WNV) particles. WNV belongs to the Flavivirus genus (Flaviviridae), which contains a growing number of zoonotic viruses transmitted by mosquitoes or ticks. WNV is found in Africa, Europe, the Middle East, Asia, Australia, and, since 1999, the Americas. The primary symptoms of infection are fever, nausea, vomiting, maculopapular rash, fatigue, and central nervous system diseases such as meningoencephalitis, encephalitis, or meningitis.