Mosquitos in McHenry County have tested positive for West Nile virus, public health officials announced.
A mosquito pool collected from Lake in the Hills on June 2 tested positive for the virus, making the pool the first mosquitoes to test positive for West Nile for the 2025 season, the McHenry County Department of Health said.
No human cases have been reported so far this year in McHenry County.
Most people exposed to the virus do not develop symptoms, though illness typically occurs two to 14 days after the bite of an infected mosquito, the department said.
About 20% of those infected experience fevers, headaches, body aches, joint pains, vomiting, or a rash, health officials said. Severe symptoms are "very rare" and include neck stiffness, coma, muscle weakness, vision loss, numbness, and paralysis.
Anyone 50 years old and older or with underlying health conditions like diabetes, kidney disease, hypertension or cancer are more at risk at developing severe symptoms, according to the department.
Though there is no vaccine or treatment for the virus, mild symptoms can be relieved with rest, fluids and over-the-counter medication, officials said.
The department will continue to collect and test mosquito batches through the remainder of the mosquito season, which runs from May through October.
McHenry County residents are urged to wear protective clothing outside like light-colored, long-sleeved shirts, socks and pants, health officials said. Residents are also urged to use EPA-registered insect repellents.
Culex mosquitoes, which are the primary carriers of the virus, typically breed in motionless water with high organic content, often found in artificial containers like rimless tires, abandoned swimming pools, buckets, bird baths, and clogged gutters, according to the department.
The best defense against mosquito-borne illnesses is to empty standing water from containers around your home and ensure that doors and windows have tight-fitting screens, therefore eliminating potential mosquito breeding sites, the department added.
For more information on the West Nile virus, visit www.mcdh.info or call 815-334-4585.
