Where in Chicagoland have West Nile Virus-positive mosquitoes been found?

DUPAGE COUNTY, Ill. — West Nile Virus-positive mosquitoes have been found in yet another Chicagoland county this week.

Health officials in DuPage County announced Thursday morning that West Nile Virus-positive pools of mosquitoes were collected in Roselle, Medinah, Clarendon Hills and Burr Ridge on Tuesday, May 27th.

Health officials in the county have since moved the Personal Protection Index (PPI) risk level from zero to one.

The PPI is updated each Wednesday at 3 p.m. throughout West Nile Virus (WVN) season as officials continue to collect and test mosquitoes in traps around the county.

Where have West Nile Virus-positive mosquitoes been found in Chicagoland this season?

DuPage is just the latest Chicagoland county to locate WNV-positive mosquito batches in recent weeks.

On Wednesday, health officials in McHenry County announced that they identified a mosquito batch that tested positive for West Nile Virus in Lake in the Hills on Monday.

It was the first WNV-positive mosquito batch located in the county so far this year.

Just a week before health officials said mosquitoes from a batch found in Glenview tested positive for the virus.

Officials did not specify a specific area where the batch was pulled from.

West Nile Virus in Illinois

According to the West Nile Virus dashboard maintained by the Illinois Department of Public Health, there have been no human cases reported in the state so far this year.

In 2024, the state saw 69 human cases, which resulted in 13 deaths.

How to avoid West Nile Virus

According to health officials, while there is no vaccine currently available for WNV, there are steps people can take to reduce the likelihood of contracting WNV.

While West Nile virus can be transmitted through blood transfusions and organ transplants, it is most commonly transmitted to humans through the bite of an infected mosquito.

The Illinois Department of Public Health advises residents to adhere to the following guidelines to minimize the risk of WNV exposure:

• Reduce – Residents should work to ensure that doors and windows have tight-fitting screens and should repair or replace any that have tears or openings. Residents should also work to keep doors and windows shut.

• Repel – Residents are advised to wear shoes, socks, long pants and a light-colored, long-sleeved shirt, as well as apply an EPA-registered insect repellent that contains DEET, picaridin, oil of lemon eucalyptus, or IR 3535 when outside.

The CDC notes that parents should consult a physician before using repellents on children under three.

• Report – Residents are advised to report locations where they see sitting stagnant for more than a week. If reported soon enough, the local health department or city government may be able to add larvicide to the water, to kill any mosquito larvae.

West Nile Virus symptoms

The Centers for Disease Control and Prevention say about eight in 10 people infected with WNV do not develop symptoms.

Around one in five people who become infected develop a fever, headache, body aches, joint pains, vomiting, diarrhea or rash. Most who develop these symptoms are able to completely recover, but CDC officials say fatigue and weakness can last for weeks or months.

According to the CDC, only about 1 in 150 people will develop a severe illness that impacts the central nervous system.

Officials said symptoms of severe illness usually include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.

While WNV can cause severe illness in people of any age, people over the age of 60 and those with certain medical conditions are also at greater risk.

Those who suffer severe illness could take several weeks or months to recover and the CDC said some effects may be permanent.