First human West Nile virus case confirmed in Illinois

July 24, 2012 3:40:10 PM PDT
The Illinois Department of Public Health has confirmed the first human case of West Nile virus was found in Cook County.

In July, a Cook County Health Department reported a female in her 60s became ill with West Nile virus.

"We are seeing a large increase in West Nile virus activity and this first human case is a good reminder that we all need to take precautions," said Illinois Department of Public Health Director Dr. LaMar Hasbrouck. "The mosquitoes that typically carry West Nile virus, commonly called the house mosquito, are not as noticeable as the swarms of floodwater mosquitoes we see during rainy summers. Even if it does not look like there are a lot of mosquitoes out, house mosquitoes are stealthy biters and their virus infection rate is increasing rapidly, so make sure to use insect repellent."

In May, a bird collected in Cook County and mosquito batches collected in DuPage and Cook counties were the first specimens to test positive for West Nile virus this year.

West Nile virus is transmitted through the bite of a 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.

In severe cases, meningitis, encephalitis or even death can occur. People older than 50 are at higher risk for severe illness from West Nile virus.

The Illinois Department of Public Health provided these precautions to help prevent West Nile disease or any other mosquito-borne illnesses:

    Reduce exposure:

  • Avoid being outdoors when mosquitoes are most active, especially between dusk and dawn.
  • 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, especially at night.
  • Eliminate all sources of standing water where mosquitoes can breed, including water in bird baths, ponds, flowerpots, wading pools, old tires and any other receptacles.
  • Repel:

  • When outdoors, wear shoes and socks, long pants and a long-sleeved shirt, and apply 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:

  • In communities where there are organized mosquito control programs, contact your municipal government to report dead birds and areas of stagnant water in roadside ditches, flooded yards and similar locations that may produce mosquitoes.

In 2011, a total of 34 Illinois residents contracted West Nile virus, and three died. A total of 19 counties in Illinois reported a positive West Nile virus mosquito batch, bird or human case. To date, West Nile virus positive birds, mosquitoes and one human case have been reported in 27 counties.

Additional information about West Nile virus can be found on the Illinois Department of Public Health's website at

Surveillance numbers are updated every Wednesday afternoon on

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