Public health agencies across multiple US states urged residents to take precautions against mosquito bites Sunday as West Nile virus detections expanded during peak summer transmission. The warnings followed confirmed positive mosquito samples in Cumberland County, Pennsylvania, announced by its Vector Control Office last week.

West Nile virus is spread primarily by Culex mosquitoes and typically peaks in the United States between August and early September. The US Centers for Disease Control and Prevention has identified late summer as the highest-risk window, when warm temperatures accelerate both mosquito breeding and viral replication.

State and county vector control programmes reported expanded trapping and targeted spraying in affected areas. Residents were advised to drain standing water, use repellents containing DEET, and wear long sleeves at dawn and dusk. Cumberland County officials said surveillance would continue as mosquito activity remained elevated.

Most people infected with West Nile virus experience no symptoms, but roughly one in five develop fever, and a small fraction face severe neurological illness. Health departments emphasised that adults over 60 and those with underlying conditions carry the greatest risk of serious disease.

The CDC and state health agencies said they would update case and detection counts through their surveillance systems in the coming days as the season progressed.