West Nile virus (WNV) is a mosquito-transmitted virus whose reservoir is shared between wild birds and mosquitoes. Humans are mainly infected through mosquito bites, although infection through organ transplantation and blood transfusion has been documented, as has trans-placental transmission.

After the infectious bite, an incubation period of 1–6 days precedes symptoms which tend to vary with the patient’s age: from mild fever and malaise in children, a moderately severe disease in the young (high fever, red eyes, headache and muscle ache) to meningitis/brain infection in the elderly and the debilitated. No specific therapy is available.

Since the first large outbreak in Romania in 1996, WNV infection has become recognised as a major cause of public health concern in Europe. No vaccine is currently available. The main preventive measures are aimed at reducing exposure to mosquito bites.