IMPERIAL COUNTY, CA — The Imperial County Public Health Department announced today that two local mosquito pools have tested positive for West Nile virus (WNV) and St. Louis encephalitis virus (SLEV). The WNV positive mosquito pool was identified in the Winterhaven area, while the SLEV mosquito pool was identified in the Bard area. The samples were collected on June 11, 2026, and test results were received today, June 18, 2026. These are the first positive mosquito pool detections of the year for both WNV and SLEV in Imperial County. 

 “As the weather warms up, mosquitoes become more active, which increases the risk of mosquito-borne diseases. These diseases can be serious, so it is important that individuals protect themselves from mosquito bites,” stated Dr. Stephen Munday, Health Officer. “Residents are encouraged to take steps to eliminate any standing water on their property that could serve as a breeding ground for mosquitoes.” 

The Public Health Department’s Vector Control Program maintains approximately 52 mosquito traps throughout the county. Traps are checked several times a week, and mosquito pools are tested weekly. “Our agency will continue monitoring disease activity and treat affected areas,” said Jeff Lamoure, Deputy Director of Environmental Health. “Although the positive mosquitoes were collected in specific areas, all county residents should take precautions, including using insect repellent and minimizing outdoor activity during dusk and dawn, when mosquitoes are most active.” 

WNV and SLEV are transmitted to humans through the bite of an infected mosquito. Symptoms may include fever, headache, nausea, vomiting, body aches, rash, and fatigue. While many people experience mild illness or no symptoms, both viruses can cause severe disease affecting the nervous system, including encephalitis (inflammation of the brain), particularly among older adults and individuals with weakened immune systems.  

Individuals can reduce their risk of mosquito-borne diseases by taking the following precautions:  

• Limit time outdoors during dawn and early evening.  

• When outdoors, wear loose-fitting, light-colored, long-sleeved shirts and pants when mosquitoes are most active.  

• Apply insect repellent that contains DEET, Picaridin, or oil of lemon eucalyptus according to label instructions. 

• Make sure that doors and windows have tight-fitting screens. Repair or replace screens that have tears or holes.  

• Eliminate all sources of standing water on your property that can support mosquito breeding by:  

• Draining or disposing of old tires, buckets, plastic covers, toys, or any other containers that can collect water. 

• Emptying and changing the water in birdbaths, fountains, wading pools, rain barrels, and potted plant trays at least once a week to destroy potential mosquito habitats.  

• Draining or filling temporary pools of standing water with dirt.  

• Keeping swimming pool water properly treated and circulating.  

• Contact Vector Control if you experience significant mosquito activity around your home or workplace. 

If you think you or someone in your household may be experiencing symptoms of a mosquito-borne illness, contact your healthcare provider. 

The United States Environmental Protection Agency (EPA) has a useful search tool that the public can use to find the repellent products most appropriate for them and their families. The tool is available at: Find the Repellent that is Right for You | US EPA 

For additional information related to WNV and SLE virus, visit the California Department of Public Health’s website at: Mosquitoes and Mosquito-Borne Diseases