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