Illinois confirms first 2025 human case of West Nile virus

A downstate resident has tested positive for West Nile virus, marking the first detection of the mosquito-transmitted disease in humans in Illinois this year — and one of the earliest cases of the sometimes fatal illness in nearly a decade.

The person was hospitalized due to complications from the infection, the Illinois Department of Public Health announced Tuesday.

About one in five people develop a fever and flu-like symptoms after contracting West Nile virus. One in 150 people develop a severe illness that can affect the brain, spinal cord, nerves and even cause paralysis. The virus poses the greatest risk to people over 65 or the immunocompromised.

Last year, the first human case of West Nile virus was detected in mid-July. This year’s first human-detected case comes more than three weeks earlier — the earliest since 2016, according to the health department. The first mosquitoes in Cook County tested positive for the virus earlier in June.

“The fact that we are seeing the first human case of West Nile virus so early in the season serves as a timely reminder — especially for seniors and those with weakened immune systems — to protect yourself from illnesses caused by mosquito bites,” IDPH Director Sameer Vohra said in a statement.

Last year, 13 people died from West Nile virus in the state, among 69 confirmed human cases, according to the state health department. That’s the highest number since 17 West Nile-related human deaths were recorded in 2018.

So far this year, West Nile virus has been found in 19 Illinois counties. The first positive mosquito batch was found May 9 in Rockford.