West Nile virus: an overview of current information

West Nile Virus (WNV) is a vector-borne flavivirus primarily infecting mosquitoes, birds, horses and humans. WNV is responsible for asymptomatic infections or a variety of clinical manifestations ranging from mild febrile illness to neuroinvasive disease. The frequency and severity of WNV-related disease have lately increased in the European Union and in the neighbouring countries, with particular concern for the Mediterranean area. This trend is probably connected to a raise in both average temperatures and rainfall, favourable factors for WNV spread. Due to the marked and expanding geographical distribution of the vector and the high endemic potential of WNV, this virus is worldwide considered an increasing public health apprehension. An augmented burden of WNV severe illness has been reported. Alarmingly, no vaccine or specific antiviral treatments are currently available for WNV infection. Hereafter, we will review the available information summarizing molecular biology, pathogenesis, clinical manifestations, epidemiology, diagnosis and therapy for WNV infection in humans.