West Nile virus (WNV) is transmitted through the bite of an infected mosquito. In rare instances, WNV can be transmitted through organ transplants, blood transfusions or from mother to child during pregnancy. Symptoms usually develop 2 to 14 days after receiving a bite from an infected mosquito.
Approximately 80% of those infected with WNV do not show any symptoms. Of the 20% that do show symptoms, most experience mild illness with symptoms such as:
Less than 1% of those infected with WNV experience severe illness involving the central nervous system. The risk of exposure to WNV around the home can be reduced by eliminating mosquito breeding sites, including standing water in places such as bird baths, eavestroughs, flower pots and discarded tires; by wearing protective clothing; always using mosquito repellent when outdoors at dawn and dusk; and by preventing mosquito entry into the home.