IMPERIAL COUNTY, CA — The Imperial County Public Health Department announced today that three mosquito pools collected in Imperial County have tested positive for West Nile virus (WNV). Two WNV-positive mosquito pools were collected on July 5, 2026, in the City of Imperial, and one was collected on July 6, 2026, in Holtville. These are the first WNV-positive mosquito pools identified in the cities of Imperial and Holtville this year. 

 The Public Health Department’s Vector Control Program maintains approximately 52 mosquito traps throughout the county. Traps are checked several times each week, and mosquito pools are tested weekly.  

 “Our agency will continue to monitor disease activity and treat affected areas,” said Jeff Lamoure, Deputy Director of Environmental Health. “Residents should continue taking precautions, including using insect repellent and limiting outdoor activity at dusk and dawn, when mosquitoes are most active.” 

 WNV is 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, WNV can also cause severe disease affecting the nervous system, including encephalitis (inflammation of the brain), particularly in older adults and individuals with weakened immune systems.  

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

• Limit outdoor activities at dawn and dusk. 

• When outdoors, wear loose-fitting, light-colored, long-sleeved shirts and pants. 

• Apply EPA-registered 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 soil.  

  • Keeping swimming pool water properly treated and circulating.  

• Contact Vector Control if you notice unusually high mosquito activity around your home or workplace. 

If you or someone in your household develops symptoms consistent with WNV, contact your healthcare provider. 

The United States Environmental Protection Agency (EPA) provides an online tool to help people choose the insect repellent that may be right for them and their families. The tool is available at: Find the Repellent that is Right for You | US EPA 

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