DuPage County health officials said the first mosquito pools of 2026 to test positive for West Nile virus were found in Roselle, Glendale Heights and Wheaton. No human cases had been reported in the county at the time of the release.
DuPage County health officials say the first mosquito pools of the 2026 season have tested positive for West Nile virus, prompting a countywide prevention alert as mosquito activity gets underway.
The DuPage County Health Department said the positive mosquito batches were collected on May 12 in Roselle, Glendale Heights and Wheaton, and confirmed on May 18. Officials said there were no reported human West Nile cases in the county at the time of the release.
The department raised its Personal Protection Index from level 0 to level 1 after the findings.
West Nile virus is spread by infected mosquitoes. The health department urged residents to reduce standing water around homes, use insect repellent, wear long sleeves and pants when possible, and take other steps to avoid mosquito bites.
The county’s warning comes at the start of the season when mosquito surveillance typically begins to pick up. Illinois Department of Public Health’s 2026 surveillance dashboard is also tracking West Nile activity across the state.
Officials said residents should continue to monitor county guidance as the season develops and as additional mosquito pools are tested.
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