The US Centers for Disease Control and Prevention reported a rise in West Nile virus cases on Wednesday, confirming human infections across multiple states as mosquito activity peaked during the height of summer.

West Nile virus remains the leading cause of mosquito-borne disease in the continental United States. The CDC tracks cases each year through its ArboNET surveillance system, with infections typically climbing through August and September when Culex mosquito populations reach their seasonal peak.

State health departments in Texas, Arizona, California and several Midwestern states have documented both human cases and infected mosquito pools in recent weeks. Most people infected show no symptoms, but roughly one in 150 develop severe neurological illness such as encephalitis or meningitis, which can be fatal in older adults.

The CDC and local vector-control agencies recommended that residents use insect repellent containing DEET, wear long sleeves at dusk and dawn, and eliminate standing water around homes where mosquitoes breed. There is no vaccine or specific antiviral treatment for West Nile virus in humans.

A CDC spokesperson said the agency was coordinating with state health departments to monitor transmission and expand mosquito-abatement efforts, warning that warm temperatures could extend the transmission season into the autumn months.