The Release for IDPH states: The USDA defines “unaffected” as “Ongoing testing and surveillance activities demonstrate absence of disease in dairy cattle in the State."
At the same time, the agencies are reminding the public that with migration season underway, infected wild birds may be found in Illinois, and stressed the need for appropriate precautions to prevent the spread of H5N1...Do not send dying or dead birds to veterinarians, wildlife refuges, etc., for testing. Instead, notify your local health department or alert IDNR wildlife biologists in cases of five or more dead birds found in one location.

To find out more please read the release: 10-3-2025 IDPH IDOA H5N1.pdf

The release mentions notifying your local health department in cases of five or more dead birds.  The graphic below helps outline what to do in the case of finding 5 or more dead birds on your property.