The patients range from 40 to 80 years old and reside on the Northwest and South sides. The patients’ symptoms began in late July or early August, according to the Chicago Department of Public Health.

Chicago reports its first three human cases of West Nile virus in 2025, with an early state case and citywide spraying efforts underway.

Local health officials say Chicago has reached a “high risk” level of the West Nile virus because mosquitoes are testing positive earlier and could lead to a longer lasting, heightened risk this