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IDPH Reports First Mosquito Batches of 2023 to Test Positive for West Nile Virus in Park Ridge and Evanston

News – Thursday, June 1, 2023

CHICAGO – The Illinois Department of Public Health (IDPH) has confirmed the first three batches of mosquitoes to test positive for West Nile virus in Illinois in 2023, both in Cook County. The North Shore Mosquito Abatement District collected a positive batch of mosquitoes in Evanston on May 30 and the Northwest Mosquito Abatement District collected two positive mosquito batches on May 31 in Park Ridge. The first positive mosquito pool in 2022 was reported on May 24th in Roselle in DuPage County. No human cases of West Nile virus have been reported so far this year.

“The reports about the first batches of mosquitoes with West Nile virus is a good reminder that this is the time of year when Illinois residents should begin protecting themselves from vector-borne diseases,” said IDPH Director Dr. Sameer Vohra. “We urge everyone -- and especially older people and those with weakened immune systems -- to take precautions to protect themselves and their families from mosquitoes and the viruses they carry by wearing insect repellent and eliminating standing water around their home where mosquitoes breed.”

Monitoring for West Nile virus in Illinois includes laboratory tests for mosquito batches, dead birds, as well as testing sick horses and humans with West Nile virus-like symptoms.  People who see a sick or dead crow, blue jay, robin or other perching bird should contact their local county or city 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 species 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.  Most people infected with West Nile virus will not show any symptoms; however,  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.

Last year, 44 counties in Illinois reported a West Nile virus positive mosquito batch, bird, horse, and /or human case. While 34 human cases of West Nile were recorded in 2022, with eight deaths, IDPH notes human cases are underreported and do not reflect the actual number of cases.

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,  IR 3535, para-menthane-diol (PMD), or 2-undecanone 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 and data can be found at IDPH’s West Nile virus website and the West Nile virus Dashboard.