Mosquito Pool in Imperial County Tests Positive for West Nile Virus

IMPERIAL COUNTY — A mosquito pool collected in the city of Imperial has tested positive for West Nile Virus (WNV), according to a news release issued by the Imperial County Public Health Department on Friday, June 20, 2025.

The sample was collected on June 16 and confirmed positive on June 20. It marks the first positive mosquito pool for West Nile Virus reported in Imperial County this year.

As of June 20, 2025, no human cases of West Nile Virus have been reported in Imperial County.

The virus has been detected in mosquito samples in at least 13 California counties: Imperial, San Diego, Riverside, San Bernardino, Kern, Tulare, Santa Clara, Stanislaus, Alameda, San Joaquin, Sacramento, Yolo, and Placer, according to the Centers for Disease Control and Prevention (CDC).

Imperial County’s Vector Control Program operates approximately 53 traps across the region, primarily within city limits. These traps are checked several times a week, and mosquito pools are collected and tested weekly. Public health officials say monitoring and treatment will continue in areas where virus activity is detected.

West Nile Virus is transmitted to humans through the bite of infected mosquitoes, which contract the virus by feeding on infected birds. Most infected individuals experience no symptoms, though some may develop mild to severe illness. The risk of severe disease increases for older adults and individuals with compromised immune systems.

Health officials advise residents to reduce exposure by eliminating standing water, wearing insect repellent, using protective clothing during dusk and dawn, and ensuring screens on windows and doors are secure.

For mosquito concerns or general information about WNV in Imperial County, contact the Environmental Health Division at (442) 265-1888. Additional statewide information is available at WestNile.ca.gov.