Health officials are warning the public and offering tips after a batch of mosquitoes tested positive for West Nile virus for the first time this year in Lake County.
A mosquito “pool,” also known as a batch of mosquitoes, was sampled on June 24 in Highland Park and tested positive for West Nile virus.
The Lake County Health Department said on Tuesday that this mosquito pool is the first confirmed indicator of West Nile virus presence in Lake County in 2025.
“Mosquitoes are an expected part of summer, but they also carry diseases that can lead to serious illness and even death,” Lake County Health Department and Community Health Center Executive Director Chris Hoff said.
“We can take steps to ‘Fight the Bite’ to protect ourselves and our families while we enjoy all that summer has to offer,” Hoff said.
The health department recommends the public practice the “4 Ds of Defense” to protect themselves and family from mosquitoes:
- Drain: Drain standing water from items around your home, yard, and business.
- Defend: When outdoors, use an insect repellent containing DEET, picaridin, oil of lemon eucalyptus, 2-undecanone, or IR3535 and reapply according to label directions.
- Dawn and Dusk: Protect yourself all day and night, and wear repellent outdoors during these prime times for mosquito activity.
- Dress: Wear long sleeves, pants, and closed-toe shoes when outdoors to cover your skin.
Culex pipiens mosquitoes, which are the primary carriers of West Nile virus, are most abundant when the weather is hot.
Residents can help prevent these mosquitoes from breeding by eliminating areas of stagnant water from their properties.
Items like buckets, gutters and plant containers, kiddie pools, and any other items holding water around homes and businesses can become breeding sites.
The Lake County Health Department’s Mosquito Surveillance Program coordinates mosquito trapping results throughout Lake County.
Mosquitoes are tested weekly for West Nile virus. The program also monitors reports of dead birds, which can be an early sign of the presence of the virus, and investigates areas of stagnant water for the presence of mosquito larvae, specifically from the Culex mosquito.
“With the warmer weather, people spend more time outdoors and mosquitoes become active,” said Alana Bartolai, Ecological Services Program Coordinator at the Health Department.
“From late-Spring to Fall, we set traps around Lake County and monitor weekly for this public health threat,” Bartolai said.
In 2024, 154 pools or batches of mosquitoes tested positive for West Nile virus. There were six human cases of West Nile virus last year.
Since 2002, there have been 86 confirmed human cases of West Nile virus in Lake County, as well as five confirmed deaths.
Most people infected with West Nile virus have no symptoms of illness. However, some may become ill, usually 3-15 days after the bite of an infected mosquito, the health department said.
Common symptoms include fever, nausea, headache and muscle ache. In some individuals, severe illness including meningitis or encephalitis, or even death, can occur.
People older than 50 and individuals with weakened immune systems are at higher risk for severe illness from West Nile virus.
Residents can also call the health department’s West Nile hotline to report areas of stagnant water, locations of dead birds, and obtain more information on the signs and symptoms of West Nile virus.
The West Nile hotline number is 847-377-8300.