West Nile Virus and Human Cases in the United States
West Nile virus is a mosquito-borne illness that circulates in the United States each year. Most infected people develop no symptoms, but some experience fever, headache, body aches, and fatigue. In rare cases, the virus can cause severe neurologic disease, including encephalitis or meningitis.
Transmission, Risk Factors, and Geographic Distribution
The virus spreads primarily through the bite of infected Culex mosquitoes. People over 60 and those with certain medical conditions face higher risk for severe illness. Cases are reported across many states, with higher activity often occurring during warmer months when mosquito populations increase.
Prevention, Surveillance, and Reporting
Prevention focuses on mosquito control, repellent use, and eliminating standing water around homes. Public health agencies track cases through surveillance systems and issue updates during peak transmission periods. For current data and guidance, see the CDC West Nile Virus page at https://www.cdc.gov/westnile/.
