• Posted June 26, 2025

Illinois Reports First West Nile Virus Case of 2025

Illinois has confirmed its first human case of West Nile virus this year, health officials say.

The person, who lives in southern Illinois, was hospitalized with complications from the mosquito-borne virus, according to the U.S. Centers for Disease Control and Prevention (CDC).

This is the earliest West Nile virus case reported in Illinois since 2016. Health officials say it’s a sign that mosquito season is off to an early start and that people should take steps to protect themselves, WGN reported.

“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,” Dr. Sameer Vohra, director of the Illinois Department of Public Health (IDPH) said.

West Nile virus spreads through the bite of a Culex mosquito — also known as a house mosquito — that has gotten the virus while feeding on an infected bird.

Most people who get the virus don’t have any symptoms. But some may have fever, nausea, headaches or muscle aches that last from a few days to several weeks.

In rare cases, the virus can cause serious health problems like paralysis or meningitis. 

People over 60 or those with weak immune systems are more likely to get very sick.

About 1 in every 150 people infected develops severe symptoms that can affect the brain, spinal cord and nerves.

So far in 2025, mosquitoes carrying the virus have been found in 19 counties across Illinois. The first batch of virus-positive mosquitoes this year was discovered in Rockford, Ill., on May 9.

In 2024, the state had 69 confirmed human cases of West Nile virus, including 13 deaths — the highest number of deaths since 2018, WGN reported.

A county is considered “positive” for the virus if it’s found in a mosquito, horse or person living there.

Illinois counties reporting the virus this year include:

Bureau, Christian, Clinton, Cook, DeKalb, DuPage, Fulton, Grundy, Hancock, Henry, Marshall, McDonough, McHenry, Peoria, Scott, Stark, Tazewell, Wayne and Winnebago.

Last year, West Nile virus was found in 72 of Illinois’ 102 counties, WGN said.

The Illinois Department of Public Health reminds people to "Fight the Bite" with the “Three R’s”:

• REDUCE places where mosquitoes breed. Get rid of standing water in flowerpots, old tires, bird baths and wading pools. Fix torn screens and keep doors and windows closed if possible.

• REPEL mosquitoes by wearing long sleeves, pants and insect repellent. Use products with DEET, picaridin, oil of lemon eucalyptus, IR 3535, para-menthane-diol (PMD) or 2-undecanone. Always follow label directions, and ask your doctor before using repellents on babies.

• REPORT standing water that doesn’t drain for more than a week, such as roadside ditches or flooded yards. Your local health department may be able to treat the area to stop mosquitoes from breeding.

More information

The Cleveland Clinic has more on West Nile virus.

SOURCE: WGN, June 24, 2025