55 ILCS 5/5-20001
The board of county commissioners in counties not under township organization, and the supervisor, assessor and town clerk of every town in counties under township organization, shall constitute a board of health, and on the breaking out of any dangerously communicable diseases in their county or town, or in the immediate vicinity thereof, it may make and enforce such rules and regulations tending to check the spread of the disease within the limits of the county or town as may be necessary; and for this purpose the board may quarantine any house or houses or place where any infected person may be, and cause notices of warning to be put thereon, and require the disinfection of the house or place: Provided, that nothing in this Division shall apply to any territory lying within the corporate limits of any city or village: Provided, further, that in case the board of health in any county not under township organization, or of any township in counties under township organization fails, refuses or neglects to promptly take the necessary measures to preserve the public health, or in case any such board of health refuses or neglects to carry out the rules and regulations of the Department of Public Health, that thereupon the Department of Public Health may discharge such duties and collect from the county or township, as the case may be, the reasonable costs, charges and expenses incurred thereby.
No board of health constituted under this Division shall function in any county during the period that Division 5-25 is in force in that county.
55 ILCS 5/5-20001