The first mosquitoes to test positive for West Nile virus in Illinois this year were reported on May 24 in Roselle in DuPage County. Since then, six more counties have reported batches of mosquitos that tested positive for the disease.

The Illinois Department of Public Health (IDPH) is reminding the public that along with summer, Mosquito season is underway in Illinois and that positive batches of West Nile Virus have been reported in seven counties around the state. The reminder comes as public health officials around the country are highlighting the importance of taking protective action to “Fight the Bite.”

While no human cases of West Nile virus have been reported in Illinois so far this year, there were 64 human cases (which are significantly under-reported) and five deaths attributed to the disease in the state in 2021.

“West Nile virus is a serious illness, and we want to remind everyone to protect themselves from mosquito bites at this time of year when so many of us are spending more time outdoors,” said IDPH Acting Director Amaal Tokars.  “The most important things we can do are to wear insect repellent if we are spending time outside and eliminate standing water where mosquitos breed around our homes. These precautions are especially important for those with weakened immune systems”

The first mosquitoes to test positive for West Nile virus in Illinois in 2022 were reported on May 24 in Roselle in DuPage County. Since then, six more counties — Cook, Will, Logan, Edgar, Macoupin and Washington — have reported batches of mosquitos that tested positive for West Nile virus. Updates on where cases have been reported can be found on the IDPH West Nile Virus Surveillance page.

In 2021, the first mosquitoes to test positive for West Nile were collected on June 9 in Skokie. Last year, 48 counties in Illinois reported a West Nile virus positive mosquito batch, bird, horse, and /or human case

Monitoring for West Nile virus in Illinois includes laboratory tests for mosquito batches, dead crows, blue jays, robins and other perching birds, as well as testing sick horses and humans with West Nile virus-like symptoms.  People who see a sick or dying crow, blue jay, robin or other perching bird should contact their local health department, which will determine if the bird will be picked up for testing.

West Nile virus is transmitted through the bite of a Culex pipiens mosquito, commonly called a house mosquito, that has picked up the virus by feeding on an infected bird.  Common symptoms include fever, nausea, headache and muscle aches.  Symptoms may last from a few days to a few weeks.  However, four out of five people infected with West Nile virus will not show any symptoms.  In rare cases, severe illness including meningitis, encephalitis, or even death, can occur.  People older than 60 and individuals with weakened immune systems are at higher risk for severe illness from West Nile virus.

IDPH encourages the public to Fight the Bite by practicing the three “R’s” – reduce, repel, and report:

Reduce

Make sure doors and windows have tight-fitting screens.  Repair or replace screens that have tears or other openings.  Try to keep doors and windows shut. Eliminate, or refresh each week, all sources of standing water where mosquitoes can breed, including water in bird baths, ponds, flowerpots, wading pools, old tires, and any other containers.

Repel

When outdoors, wear shoes and socks, long pants and a light-colored, long-sleeved shirt, and apply an EPA-registered insect repellent that contains DEET, picaridin, oil of lemon eucalyptus, or IR 3535 according to label instructions.  Consult a physician before using repellents on infants.

Report

Report locations where you see water sitting stagnant for more than a week such as roadside ditches, flooded yards, and similar locations that may produce mosquitoes.  The local health department or city government may be able to add larvicide to the water, which will kill any mosquito larvae.

Additional information about West Nile virus can be found on the IDPH website.