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Enhanced Surveillance Unit

The Enhanced Surveillance Unit (ESU) monitors seasonal diseases including West Nile Virus and Influenza, manages the syndromic surveillance program, and provides epidemiologic support to the Community Preparedness and Coordination Unit.

The ESU manages and interprets all important pieces of West Nile Virus surveillance including mosquito data, bird data, and human case data for the prevention and control of West Nile Virus in the community.

Influenza is monitored each season via a syndrome, influenza-like-illness. Influenza-like-illness is defined by the CDC as symptoms of fever (greater than 100oF) with cough or with sore throat, without another known cause other than influenza. Data is captured from sentinel hospitals, sentinel physicians, and syndromic surveillance participating hospitals each week. A summarized report of influenza-like-activity for suburban Cook County is provided on a weekly basis from October through May.

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West Nile Virus

West Nile Virus first emerged in the United States in the New York metropolitan area in the fall of 1999. Since then, the virus, which can be transmitted to humans by the bite of an infected mosquito, has quickly spread westward across the country. In Illinois, West Nile virus was first identified in September 2001 when laboratory tests confirmed its presence in two dead crows found in the Chicago metropolitan area.

In 2002, birds, mosquitoes and horses in 100 of the state's 102 counties were reported positive for West Nile virus and the first human cases and deaths from West Nile virus illness in Illinois were reported in August 2002. By the end of the year, the state led the nation with more than 800 human cases and 64 deaths. Thirty-eight of those deaths were in Chicago and suburban Cook County.

The 2003 season was far more mild with only 12 confirmed human cases of West Nile Virus in suburban Cook County. However, the unit still received over 1500 inquiries related to animal and human deaths and proper prevention methods.

In an effort to continue to answer questions of public concern and to keep the public safe from West Nile Virus in the future, we continue to run prevention programming. The Cook County Department of Public Health Vector Control Program maintains an environmental surveillance program to monitor dead perching birds.

Mosquito surveillance is maintained by the four Mosquito Abatement Districts (MAD) serving suburban Cook County. These are separate taxing bodies that are regulated by the Department of Agriculture, not the Cook County Department of Public Health. The districts conduct surveillance to locate and control or eliminate mosquito breeding sources. The districts serving suburban Cook County are the Des Plaines Valley Mosquito Abatement District, North Shore Mosquito Abatement District, Northwest Mosquito Abatement District and South Cook County Mosquito Abatement District.

Illinois Department of Public Health: West Nile Virus

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West Nile Virus Resources

West Nile Virus Flyers

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West Nile Virus: Frequently Asked Questions

What is West Nile virus?

An infection carried by mosquitoes. People get WNV from the bite of a mosquito that is infected with WNV. Mosquitoes become infected when they feed on a bird that has the virus in its blood. Once infected the mosquito can spread the virus to humans and other animals.

Who can get WNV?

Anybody can become infected with WNV so it's important to protect yourself from mosquito bites. People over the age of 50 and those with chronic diseases such as heart disease or cancer may be more at-risk for serious illness. Most human cases occur in the late summer and early fall.

What are the symptoms?

Most people infected with WNV have no symptoms of illness and never become ill. Some people may become ill 3-15 days after being bitten by an infected mosquito. Symptoms may include fever, headache and body aches. More severe symptoms may be a high fever, stiff neck, confusion and muscle weakness.

Should we stay indoors?

It is not necessary to limit outdoor activities unless there is evidence of mosquito-borne disease in your area. However, you can and should try to reduce the risk of being bitten by mosquitoes.

How can I help protect my family and myself from mosquitoes and the diseases they may carry?

During the summer, mosquitoes can develop in any standing water that lasts more than seven to 10 days. Consequently, you can begin protecting your family from mosquitoes by reducing the amount of standing water available for mosquito breeding around your home

How can I fight the bite?

Don't allow mosquitoes to breed!

  • Empty plastic wading pools weekly or store upside down when not in use.
  • Change water every few days in bird baths and plant saucers.
  • Store boats covered or upside down.
  • Water bowls for pets should be emptied and refilled daily.

Also...

  • Keep weeds and grass cut short.
  • Be sure screens in homes are in good repair and tight fitting.
  • Keep gutters around your home clean and in good repair.
  • Limit time outdoors when mosquito activity is heaviest (dusk to dawn).
  • If outside, wear socks, shoes, long pants and a long-sleeved shirt. Loose-fitting, light colored clothing is best.
  • Use repellents containing 25-35% DEET (N,n-diethyl-meta-toluamide). Always follow label directions. Talk to your doctor before applying repellent to infants or children.
  • Protect babies and small children by using mosquito netting over strollers.

What if I find a dead bird?

The presence of dead perching birds in a community is a sign of possible WNV in the area. If you find a dead bird, please call 708-492-2650 to report your sighting. CCDPH staff will determine if they need to pick up the bird for laboratory testing.

What do perching birds look like?

Perching birds are:

  • Blue jay
  • Mockingbird
  • Cardinal (male)
  • Robin
  • Cardinal (female)
  • Sparrow
  • Catbird
  • Starling
  • Crow
  • Swallow
  • Finch
  • Warbler
  • Flycatcher
  • Wren
  • Grackle

The Emergence of West Nile Virus During a Large Outbreak in Illinois in 2002,
A Journal of The American Journal of Tropical Medicine and Hygiene.

Rhabdomyolysis in Patients with West Nile Encephalitis and Meningitis,
Vector-Borne and Zoonotic Diseases, Sept. 2005, Vol. 5, No. 3: 252-257.

Archived WNV surveillance reports:

Related Links:

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