An adult DuPage County resident has tested positive for West Nile virus, the first confirmed human case in the county this year.
The DuPage County Health Department (DCHD) announced the case Tuesday, Sept. 1, but did not release the patient's name, age or hometown, Patch reported. The department's Personal Protection Index, a 0-to-3 scale tracking local virus activity, jumped to level 2, or moderate, because of the confirmed infection and a higher number of mosquitoes testing positive across the county.
The announcement came the same day the Chicago Health Department reported the state's first West Nile death of 2026, along with two additional human cases in Chicago, according to NCTV17. Neighboring Cook County had reported four human cases as of Aug. 28.
Illinois Department of Public Health Director Dr. Sameer Vohra said in a Sept. 1 news release, "While most people won't experience serious symptoms, West Nile virus can lead to severe illness in high-risk groups such as older adults, individuals with chronic medical conditions, and immunocompromised persons."
About one in five people infected develop flu-like symptoms including headaches, body aches, fever and nausea. Less than 1% develop severe illness affecting the central nervous system.
Local mosquito spraying
Downers Grove and Westmont have both deployed Clarke Mosquito Control to spray for adult mosquitoes this season. Downers Grove sprayed all incorporated streets on Aug. 12 after multiple trap samples tested positive for the virus. Positive results were also trending upward in surrounding communities, the village said.
Westmont's next spray is Sept. 4. The village has its third community-wide mosquito treatment scheduled between dusk and dawn that Friday. The truck-applied products are OMRI-listed, meaning they are approved for organic use in residential areas.
How to protect yourself
DCHD officials are urging residents to follow four steps:
- Drain standing water around your property, including in flower pots, gutters and bird baths.
- Use DEET insect repellent when outdoors.
- Dress in long sleeves and pants to reduce exposed skin.
- Avoid outdoor activity between dusk and dawn, when mosquitoes are most active.
The DCHD updates its Personal Protection Index every Wednesday by 3 p.m. at dupagehealth.org. Residents can reach the department at (630) 682-7400.
Westmont residents can sign up for advance mosquito-spraying alerts at clarkeportal.com. Downers Grove residents who want to opt out of spraying can call Clarke at 1-800-942-2555, Option 4.
