An unknown and potentially fatal respiratory illness is infecting dogs in the United States, with cases reported in at least 10 states, according to multiple media reports.

Veterinarians from states including Oregon, New Hampshire, California, and Colorado are urging owners to decrease their pets’ contact with dogs outside the household and to ensure their pets are up to date with vaccinations.

According to reports, the illness — being termed Atypical Canine Infectious Respiratory Disease (aCIRD) — can begin with a cough, but may quickly lead to pneumonia and respiratory distress.

US News & World Report says the illness does not respond does not respond to antibiotics and features symptoms of respiratory illness such as coughing, sneezing, nasal or eye discharge and lethargy. The report also noted some cases of pneumonia progress quickly, making dogs very sick within 24 to 36 hours.

In an interview with Today.com, Colorado Springs veterinarian Dr. Lindsey Ganzer said, “It seems to happen very, very quickly — to go from this cough that just won’t go away … and then all of a sudden they develop this pneumonia,” NBC Los Angeles reported. Ganzer added that her facility has seen approximately 30 cases of the canine respiratory condition since mid-October, including 4-5 deaths. She told Today.com that “Dogs are most likely to contract the infection by being in close contact with numerous other dogs — so places like day care, dog parks, groomers or boarding kennels,” NBC Los Angeles reported.

According to a press release from the American Veterinary Medical Association (AVMA), the cases in Oregon appeared during the summer in the Portland metro area, but no cause for the illness has been identified.

“Based on the epidemiology of the cases reported at this point, the cases appear to share a viral etiology, but common respiratory diagnostic testing has been largely negative,” the Oregon Department of Agriculture wrote in an email to the AVMA. “A handful of cases do test positive for M. cynos, but that agent is not believed to be the underlying causative agent.”

According to the Los Angeles County Department of Public Health, vets are currently classifying cases of aCIRD as a those with a negative canine respiratory PCR test panel but one of the following clinical scenarios:

  • Chronic mild-moderate respiratory infection that lasts more than six weeks that is minimally or not responsive to antibiotics;
  • Chronic pneumonia that is minimally or not responsive to antibiotics; or
  • Acute pneumonia that rapidly becomes severe and often leads to poor outcomes in as little as 24-36 hours.

In Los Angeles, 10 cases have been reported to the County’s Veterinary Public Health Program since November 16, 2023. The department advises pet owners to do the following for any symptomatic dogs:

  1. Contact their pet’s veterinarian so the pet may be evaluated, and, if indicated, the appropriate tests and medications may be provided.
  2. Isolate sick dogs at home for a minimum of 28 days past the first day of the onset of illness. Dogs exposed to the sick dog should quarantine at home and away from other dogs for 14 days to monitor them for signs and symptoms of illness.
  3. Clean regularly and disinfect surfaces, doorknobs, keyboards, and animal equipment. To disinfect, use an EPA-registered disinfecting product or a stronger bleach solution.
  4. Keep the dog home and away from day care, boarding kennels, grooming facilities, and dog parks.
  5. If a dog becomes ill after being boarded or being in a facility, owners should take it to a veterinarian for evaluation and they should also notify the facility about the illness.