Lake County has reported the first confirmed presence of West Nile virus in 2025. A mosquito pool collected on June 24 at a Southlake Mosquito Abatement District trap in Highland Park tested positive for the virus.
According to Lake County, residents are advised to follow the “4 Ds of Defense” to protect against mosquitoes: drain standing water from items around homes, yards, and businesses; defend by using insect repellents containing DEET, picaridin, oil of lemon eucalyptus, 2-undecanone, or IR3535; avoid exposure during dawn and dusk; and dress in long sleeves, pants, and closed-toe shoes. Culex pipiens mosquitoes, the primary carriers of West Nile virus, breed in stagnant water found in buckets, gutters, plant containers, kiddie pools, and similar items.
Most individuals infected with West Nile virus do not show symptoms. However, illness can develop within 3 to 15 days after a bite from an infected mosquito. Common symptoms include fever, nausea, headache, and muscle aches. Severe illness such as meningitis or encephalitis can occur, particularly in people over 50 or with weakened immune systems.
Chris Hoff, executive director of the Lake County Health Department and Community Health Center said that “mosquitoes are an expected part of summer,” but they also carry diseases that can lead to serious illness and even death. Hoff emphasized that steps can be taken to “Fight the Bite” to protect individuals and families while enjoying summer activities.
The Lake County Health Department’s Mosquito Surveillance Program coordinates mosquito trapping throughout the county and tests mosquito pools weekly for West Nile virus. The program monitors reports of dead birds as early indicators of virus presence and inspects stagnant water areas for Culex larvae. In 2024, 154 out of 723 mosquito pools tested positive for West Nile virus with six confirmed human cases. Since 2002, Lake County has recorded 86 human cases of West Nile virus and five deaths.
