Dog Tests Positive for Rabies, Marking Illinois’s First Case in Decades

The dog, which was younger than a year old, began showing troubling signs earlier this month.

Published: 12/23/2025, 10:31:46 PM EST

Dog Tests Positive for Rabies, Marking Illinois’s First Case in Decades — A dog in a stock photo. (Shutterstock)

For the first time in nearly three decades, a dog in Illinois has tested positive for rabies.

The case, confirmed just days before Christmas, involves a puppy in Chicago, according to an Illinois Department of Public Health (IDPH) notice released Dec. 22.

The dog, which was younger than a year old, began showing troubling signs earlier this month. The dog had a history of behavioral issues but the situation deteriorated on Dec. 16. The IDPH reported that the dog exhibited "growling, snapping, increased barking and anxiety."

Just days prior, on Dec. 11, the dog had bitten a person. Because state law requires animals that bite humans to be observed for 10 days or tested, the dog underwent testing after being euthanized on Dec. 18.

On Dec. 19, the IDPH Chicago lab confirmed the presence of the rabies virus using direct fluorescent antibody testing, and a repeat test confirmed the result. The agency said this is the first rabid dog identified in the state since 1994, and the first in Cook County since before 1964.

Health officials are now investigating the source of the infection. The puppy was adopted from a Chicago household but came from a litter sent to a Chicago rescue from a Florida rescue group in May 2025. Although the dog received a rabies vaccination in June 2025, officials believe it is possible the dog was exposed to a rabid animal before it was vaccinated.

The agency said that the owners were not aware of any known contact with wild animals, such as bats, while the dog lived with them.

Scientists are currently performing strain typing to determine if the virus matches strains typically found in bats, foxes, or raccoons. Bats are currently the primary reservoir for animal rabies in the state. The last time a skunk tested positive in Illinois was 1998, and the last raccoon case was in 1983.

The Chicago Department of Public Health and IDPH are checking on humans who interacted with the dog to determine if they need post-exposure prophylaxis (PEP) treatment. Meanwhile, Cook County Animal and Rabies Control is following up with the owners of the puppy's littermates and tracing other dogs that might have been in contact with the puppy, including those at a doggy day care.

Any vaccinated dog that had contact with the rabid puppy must receive a booster shot and enter a 45-day home quarantine with strict monitoring for symptoms.

This case in Chicago is not the only recent resurgence of the virus in the Midwest. The Missouri Veterinary Medical Association reported in November that a dog in McDonald County, Missouri, tested positive in mid-November. That case marked the first time a dog in Missouri had contracted the virus in nearly seven years.

On a national level, the fight to contain the virus is costly and ongoing. The U.S. Department of Agriculture (USDA) announced earlier this summer that managing rabies detection and control can cost more than $500 million annually. The USDA noted that about 90 percent of reported rabies cases in the United States occur in wildlife.

In August 2025, federal officials began distributing oral rabies vaccine baits by airplane and helicopter across rural and suburban areas in the eastern United States to prevent raccoon rabies from spreading into "America’s heartland."

Rabies remains a severe threat. According to the USDA, the virus is "almost always fatal once symptoms appear," though it is 100 percent preventable if humans seek medical help immediately after being exposed.

For pets, the warning signs are grim. The McDonald County Health Department said early symptoms include sudden changes in behavior and "unexplained progressive paralysis." Later stages can involve aggression, difficulty swallowing, and excessive drooling. The IDPH notes that the incubation period in animals usually lasts 20 to 60 days but can stretch up to a year.