Illinois seeing cases of a pest-borne virus early this year. How to protect yourself
Summertime heatwaves bring many pest species to Illinois, including ants and ticks, but one species stands out as the “world’s deadliest organism.”
Mosquitoes pose a significant threat to public health due to the variety of dangerous and potentially fatal diseases they spread, Mike Bentley, vice president of training and technical services for the National Pest Management Association and board certified entomologist, said in a July 14 interview with the Belleville News-Democrat.
The leading cause of mosquito-borne disease in the continental U.S. is West Nile virus, according to the U.S. Centers for Disease Control and Prevention. Most people who are infected with the virus are asymptomatic, but others can develop fever, and about 1 in 150 people who are infected develop a serious and sometimes fatal illness.
An individual from southern Illinois was hospitalized due to complications from West Nile virus, the Illinois Department of Public Health reported June 24. That case marked the state’s first human case in 2025 and represented the earliest onset of the disease in Illinois since 2016.
“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 Dr. Sameer Vohra said in the press release. “I encourage all Illinoisans to ‘Fight the Bite’ and take precautions to protect themselves and their loved ones.”
IDPH has reported two cases of West Nile virus in humans so far in 2025 as of July 16. The state agency says its numbers may differ from the U.S. Centers for Disease Control and Prevention’s due to the timing of the reports. Illinois’ total case count appears to be three so far, as the DuPage County Health Department reported another human case July 24.
In 2024, Illinois reported 69 confirmed human cases of West Nile virus and 13 deaths.
People who are older than 60 or have weakened immune systems are most at risk of severe illness resulting from a West Nile virus infection, the health department reports.
West Nile virus is probably the most concerning illness mosquitoes can vector in Illinois, but in other parts of the world greater concerns are the spread of Zika virus, malaria, dengue and yellow fever from mosquito bites.
How to protect yourself against mosquitoes
This time of year is when we see the highest pest pressure for mosquitoes, as well as ticks, Bentley said.
“We’re just now getting into peak mosquito season, where it’s nice and warm,” Bentley said.
All mosquitoes need to complete their life cycle is about a bottlecap’s worth of water, so eliminating any sources of standing water in your backyard is an important mitigation strategy for the pests.
Another way to protect yourself against bites and the viruses they can transmit is to wear long pants and long-sleeved shirts, Bentley added. It can also be helpful to wear an insect repellent with an EPA-registered active ingredient, such as DEET or picardin.
High-speed fans on your patio or deck can also mitigate mosquito interactions as the strong airflow disrupts their flight. This will likely only provide immediate protection in a small area, Bentley said.
To protect yourself against ticks, you might consider wearing light-colored clothing so you can identify them more easily.
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