Public health officials have confirmed that mosquito samples from McHenry and DuPage Counties have tested positive for West Nile virus (WNV) — marking the first positive mosquito pools of the 2025 season in Illinois.

Mosquitoes collected in Lake in the Hills (McHenry County) and in Roselle, Medinah, Clarendon Hills, and Burr Ridge (DuPage County) tested positive in late May and early June. No human infections have been reported so far this year.

What You Need to Know

• Symptoms: Most people don’t develop symptoms. About 1 in 5 may experience fever, headaches, or rashes. Severe symptoms are rare but can include vision loss, paralysis, and coma.
• Risk factors: Adults over 50 and those with preexisting conditions (e.g., diabetes, cancer, hypertension) are more vulnerable.
• Season: Mosquito season runs May through October. WNV activity typically rises in warmer months.

How to Protect Yourself

• Drain standing water weekly from birdbaths, planters, buckets, and gutters.
• Use EPA-registered insect repellent and wear long sleeves and pants when outdoors.
• Ensure window and door screens are secure and intact.

In 2024, Illinois reported 69 human WNV cases and 13 deaths, including five deaths in suburban Cook County.

Stay alert and take steps to protect your family from mosquito-borne illness.