West Nile virus (WNV) is an infection that is most commonly spread by a mosquito bite. In rare cases, WNV can lead to serious complications, or death.

This infection is found worldwide. In the United States, it tends to occur during late summer and early fall.

West Nile is caused by a virus. The virus is passed through the bite of an infected mosquito. The virus can also be passed through a blood transfusion with infected blood, but this is rare.