West Nile virus has been confirmed in environmental samples from 17 counties across Illinois since the beginning of the year, according to the state Department of Public Health. No human cases have been reported yet in 2025.
“With mosquito season underway in Illinois, it is now time for Illinoisans, especially seniors and thosewith weakened immune systems, to start taking precautions to prevent mosquito bites,” IDPHDirector Dr. Sameer Vohra said in a June 18 press release. “A bite from a mosquito infected with WNV can cause serious illness.”
Here’s what we know.
Where was West Nile virus found in Illinois?
A county is considered positive for West Nile virus if a mosquito, horse or human from that county testspositive for the virus, according to the department.
The following counties reported the virus:
The first mosquito batch that tested positive for the virus this year was found on May 9 in Rockford.
What is West Nile virus?
West Nile virus is transmitted through the bite of a Culex mosquito, or house mosquito, that has picked up the virus by feeding on an infected bird, according to the IDPH. Common symptoms include fever, nausea, headache and muscle aches, which may last from a few days to a few weeks.
Most people infected with the virus will not display any symptoms. But in rare cases, severe illness, including meningitis, encephalitis, or even death, can occur. People 60 years and older and those with weakened immune systems are at higher risk for severe illness.
How to protect yourself from West Nile virus
The IDPH recommends practicing the three “R’s” — reduce, repel and report.
How many West Nile virus cases last year in Illinois?
There were 69 confirmed human cases of West Nile virus in 2024, including 13 deaths, according to the IDPH. This was the highest number since 2018, when 17 virus-related human deaths were recorded.
The virus was confirmed in 72 counties in Illinois last year.
This article originally appeared on Journal Star: West Nile virus found in Peoria, 16 other Illinois counties. Here’s where, how to protect yourself
Reporting by Hannah Hudnall, USA TODAY NETWORK / Journal Star
USA TODAY Network via Reuters Connect
