The Stickney Township Animal Control issued the warning to be on the lookout for raccoons that are "not moving and just staring, growling showing their teeth, crawling in circles," according to the department's Facebook post on Friday.
Infected animals are sometimes called "zombie raccoons" and were reported in Cook County last spring, as well as in Ohio.
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Distemper causes coughing, tremors and seizures and leads raccoons to lose their fear of humans.
People should not approach the animals and keep dogs and children away. Also, do not try to feed them.
Dog owners should ensure that their pet is vaccinated with the distemper virus shot. The virus can be fatal to dogs.