A dog in Chicago tested positive for rabies, marking the first time in more than 60 years that a dog tested positive for the viral disease in Cook County.
The dog, vaccinated for rabies in June, showed a change in behavior and was euthanized before testing positive, the county’s Department of Animal and Rabies Control said in a statement Tuesday.
The case is the first positive test in Cook County since 1964, and the first in Illinois since 1994, according to the department.
It’s unclear how the vaccinated dog contracted rabies. The county said it is studying the issue and will share its findings to “inform public education efforts to prevent future cases.”
It’s possible the dog was exposed to rabies before it was vaccinated, or was exposed within the 30 days it takes for a rabies vaccination to provide protection, according to Megan Carolan, a veterinarian and deputy administrator with Cook County Animal and Rabies Control.
Rabies has a long incubation period — the time between exposure and first symptoms — that can span from a month or two on average, but in some cases can be as long as six months to a year or longer, she said.
“Rabies is kind of a strange virus in which the incubation period can be quite variable from patient to patient,” Carolan said.
The dog, born in Georgia, was taken to a Chicago rescue shelter and adopted by a Chicago family, according to the county’s statement. He was less than a year old, and was part of a litter of puppies sent to Chicago from a southeastern United States rescue group, according to a Illinois Department of Public Health memo.
The dog then bit someone on Dec. 11 before it was euthanized, according to the memo.
Thirteen people who had contact with the dog have not shown symptoms and are being given preventative treatment, according to the county. The risk to the public and their pets is low, they said.
Rabies is a progressive neurological disease that is fatal, but also preventable and treatable, according to public health officials. The virus slowly climbs up the body’s nerves until it attacks the central nervous system or the brain. Rabies causes madness, convulsions and loss of muscle control. Patients with rabies eventually slip into a coma and die.
People and pets usually contract rabies from wildlife. It spreads though saliva from an infected animal to people, most commonly through a bite, health officials say. Rabies can also spread by saliva through open wound or the eyes, nose or mouth. It can take weeks to over a year for a rabies exposure to become an infection.
Luckily, post-exposure treatments are very effective for people and animals, as long as they’re administered quickly, says Emily Landon, an infectious disease doctor with the University of Chicago Medicine.
“This was a one-off, rare event, but it’s an important reminder,” Landon said. “It’s really important to get your dogs and cats vaccinated for rabies. That’s why we haven’t had a case in so long.”
The Chicago Department of Public Health and Illinois Department of Public Health are also investigating the cause of the positive case, according to the county’s statement.