IDPH Reports First 2 Mosquito Batches to Test Positive in 2024 for West Nile Virus in Cook & Morgan Counties

CHICAGO – The Illinois Department of Public Health (IDPH) announced today that it has confirmed the first two batches of mosquitoes to test positive in 2024 for West Nile virus in Illinois, one in Hoffman Estates in Cook County and one in Morgan County.

The specimen in Hoffman Estates was collected by the Northwest Mosquito Abatement District on May 14. A second batch to test positive was found May 16 in Jacksonville in Morgan County. The confirmation of the first two mosquito batches follows a mild winter and spring and comes two weeks earlier than in 2023. IDPH recently reported that the first bird to test positive form West Nile virus was found April 2 in Douglas County.

“The report of the first two batches to test positive for West Nile virus serves as a timely reminder for Illinoisans to begin protecting themselves from vector-borne diseases,” said IDPH Director Dr. Sameer Vohra. “It is important for everyone - and especially older people and those with weakened immune systems - to safeguard themselves and their families from mosquitoes and the viruses they carry by wearing insect repellent and eliminating standing water around their home. You can ‘Fight the Bite’ by practicing the three R’s – reduce, repel, and report.”

Monitoring for West Nile virus in Illinois includes laboratory tests for mosquito batches and 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 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, 67 Illinois counties reported a West Nile virus positive mosquito batch, bird, horse, and/or human case, up from 44 counties in 2022. Last year, there were 119 human cases of West

Nile virus and six deaths reported in Illinois, according to provisional data, compared to 33 human cases and seven deaths in 2022. 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 to your local health department 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.