The Oak Park Health Department has found West Nile virus in mosquitoes collected from south Oak Park, marking the community's first positive test of 2026 and an earlier detection than several nearby communities this year.
The department announced Wednesday, June 17, that mosquito pools collected June 10 tested positive for the virus. No human cases have been reported in Cook County so far in 2026, according to the Oak Park Health Department, but officials said the positive pools signal increased transmission risk to residents.
Oak Park's June 10 collection date puts the village ahead of Chicago, where the first positive mosquitoes were reported June 12, and the North Shore communities of Wilmette, Evanston, and Northbrook, which recorded their first positives June 16.
Last Year Was Severe
The early detection comes after a punishing 2025 season. Suburban Cook County recorded 33 human West Nile cases through September 2025, nearly double the 19 cases in 2024, according to the Cook County Department of Public Health. Twenty-two of those cases were neuroinvasive, affecting the central nervous system. One suburban Cook County resident in their 60s died.
Statewide, Illinois tallied 150 human cases and 10 deaths in 2025. Oak Park and River Forest both had positive mosquito traps during the 2025 season.
What Residents Should Do
There is no vaccine or medication to prevent or treat West Nile virus. About 1 in 5 people infected develop fever and flu-like symptoms; severe illness occurs in roughly 1 in 150 people, mostly in those older than 55 with weakened immune systems.
The health department urges residents to follow the "3 R's":
- Reduce standing water in buckets, gutters, planters, bird baths, and tarps where mosquitoes breed.
- Repel bites using insect repellent containing DEET, picaridin, oil of lemon eucalyptus, or IR3535.
- Report stagnant water or West Nile concerns to [email protected].
The Cook County Department of Public Health publishes weekly West Nile surveillance reports throughout the summer. More information is available at www.oak-park.us/fightthebite.
