The West Nile virus is a virus that is typically transmitted to humans through mosquito bites. In most cases, infection with the West Nile virus does not present a serious health risk. However, some people who are infected may develop a more severe form of illness that is potentially life-threatening.

Mosquitoes become infected with the West Nile virus after biting birds that carry the virus. The virus moves into the mosquitoes’ bloodstream and circulates for several days before settling into the salivary glands. The mosquitoes then go on to bite and infect people and other animals.

Rarely, the West Nile virus may be spread through blood transfusions, organ transplants, breastfeeding and transmission from a mother to her fetus. Casual contact (e.g., touching, kissing) cannot spread the virus. 

The vast majority of people who become infected with the West Nile virus display no symptoms. Within a couple of weeks, they develop antibodies that help clear the virus from their bodies and protect them against future infections. However, some patients may experience serious illness as a result of infection. Brain damage, paralysis and even death may occur.

Various tests may be performed to identify the presence of the West Nile virus. A serology test that can identify the presence of certain antibodies in the blood or cerebrospinal fluid is considered the chief method of diagnosis.

In most cases, no medical treatment is necessary. Milder cases usually resolve on their own, although this may take several weeks. In more severe cases, hospitalization may be required.

The best way to prevent infection by the West Nile virus is to avoid being bitten by mosquitoes. People are urged to use mosquito repellents that have an active ingredient such as Diethyltoluamide (commonly referred to as DEET). People can also reduce mosquito breeding grounds by eliminating standing water collected in buckets, barrels, flower pots and other containers.