West Nile virus (WNV) is a member of the Flavivirus genus and can cause neurological disease and death in people. However, approximately 80% of people who are infected will not show any symptoms. WNV is commonly found in Africa, Europe, the Middle East, North America and West Asia. WNV is maintained in nature in a cycle involving transmission between birds and mosquitoes. Humans, horses and other mammals can be infected. West Nile virus can be diagnosed by reverse transcription polymerase chain reaction (RT-PCR) assay.