Lake County Gazette

Lake County has announced that the Lake County Health Department and Community Health Center reported the first human case of neuroinvasive West Nile virus in 2025. The case involves a resident in their 70s who became ill in early July.

According to Lake County, West Nile virus was detected in nine out of 214 mosquito samples collected within the county in 2025. The virus typically peaks between July and September, coinciding with heightened mosquito activity. To mitigate exposure, residents are advised to adhere to the "4 Ds of Defense": eliminate standing water around properties, apply Environmental Protection Agency (EPA)-approved insect repellents containing ingredients like DEET or picaridin as directed, protect themselves during peak mosquito hours from dawn to dusk, and wear protective clothing such as long sleeves, pants, and closed-toe shoes.

While many infected individuals do not experience symptoms, some may develop signs of illness within three to 15 days after being bitten. Common symptoms include fever, headache, nausea, and muscle pain. In rare cases, the virus can lead to serious neurological conditions like encephalitis or meningitis. These conditions may result in symptoms such as a stiff neck, confusion, sudden weakness or numbness on one side of the body, difficulty walking, or even death. Older adults, people with weakened immune systems, and those with multiple health issues face a higher risk of severe complications from West Nile virus.

Chris Hoff, executive director of the Lake County Health Department and Community Health Center said: "Our time spent outdoors typically increases during the summer months, which also increases our exposure to mosquitoes." Hoff added: "Remember to take steps to protect yourself and your family from mosquitoes to reduce your risk of getting West Nile virus."

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—the main vector for West Nile in Illinois. In 2024, 154 out of 723 mosquito pools tested positive for the virus with six confirmed human cases. Since 2002, Lake County has recorded 86 human cases of West Nile virus and five deaths.