Mystery dog illness is spreading in these U.S. states

Many dog owners are alarmed after an urgent health warning for canines started circulating online in recent weeks.

Some viral social media posts claim a mysterious respiratory illness that’s highly contagious and potentially fatal is spreading among dogs throughout the U.S. One of the posts warns owners not to bring their pets to dog parks or other places where dogs may congregate. 

Many commenters responded to the posts with questions and concerns about the alleged illness and how it could affect their dogs. 

Is a mystery illness spreading among dogs in some states?

Yes, a mystery respiratory illness is spreading among dogs in some U.S. states.

An unknown respiratory illness is spreading among dogs in Oregon, Colorado and other U.S. states, according to veterinarians and multiple state agencies.

The illness starts out as a cough that can progress to severe pneumonia in some cases. Veterinarians say they haven’t been able to identify what’s causing the respiratory illness.

Though veterinarians have reported some deaths from the unknown illness, it is “very rarely” fatal, veterinarian and researcher David Needle told VERIFY.

Dogs that contract the unknown illness do not respond to typical treatments for another known diagnosis, according to the Washington State Department of Agriculture.

Cases of the unknown illness reported to the Oregon Department of Agriculture typically result in chronic mild to moderate inflammation of the trachea that lasts for 6-8 weeks or longer, and 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.”

Symptoms of respiratory illness in dogs usually include coughing, sneezing, nasal and/or eye discharge, and lethargy. Owners whose dogs have these symptoms should consult their veterinarian, the Oregon Veterinary Medical Association (VMA) says. 

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Where the unknown illness has been reported

Researchers are still trying to collect and verify data from samples across the country to determine exactly where the disease is spreading. 

But over the last several months, veterinarians have reported cases of what appears to be the unknown illness in these places:

• Oregon, specifically Portland and the Willamette Valley area
• Colorado, specifically Colorado Springs and Denver 

In August 2023, Oregon's agriculture department began receiving reports of an “atypical canine infectious respiratory disease” circulating in the Portland and Willamette Valley areas, the Oregon VMA says.

The Oregon Department of Agriculture has received more than 200 case reports from veterinarians since mid-August, the American Veterinary Medical Association (AVMA) reported on Nov. 17.

In a Nov. 16 article, Colorado State University’s College of Veterinary Medicine and Biomedical Sciences reported an “uptick” in cases of an unknown respiratory illness.

North Springs Veterinary Referral Center, an emergency veterinary clinic in Colorado Springs, has treated about 35 cases since October, veterinarian and CEO Lindsey Ganzer told VERIFY. A few of the dogs have died, Ganzer said. 

Other animal hospitals in nearby Denver and surrounding areas are also seeing cases of the unknown illness, Ganzer said.

Needle, who is a senior veterinary pathologist at the University of New Hampshire’s Veterinary Diagnostic Laboratory, has been studying the unknown illness for about a year. It emerged in New Hampshire in 2022, he said. 

Since then, Needle and other researchers at the university have looked at samples from Rhode Island and Massachusetts, and recently received some from Oregon. They are awaiting samples from Colorado and potentially other U.S. states, Needle said. 

The researchers are trying to figure out if the samples from various states share the same genetic makeup.

Experts share precautions for dog owners

Our experts recommend that owners make sure dogs are up to date on all of their vaccines, including canine influenza, Bordetella and parainfluenza.

While these vaccines may not target the unknown infection, “maintaining overall health through routine vaccinations can help support a dog’s immune system in combating various infections,” the CSU College of Veterinary Medicine and Biomedical Sciences article says. 

The CSU article also recommends avoiding social events for dogs, including dog parks. If owners have to take their dog to a boarding facility, groomer, or daycare, they should make sure to complete the recommended vaccinations, the article says. 

If a dog owner notices their pet has a cough, Ganzer encourages them to visit their veterinarian’s office “sooner rather than later.” Dog owners should also be on the lookout for a worsening cough, labored breathing, blue or purple gums, lethargy and weakness, and decreased appetite, Ganzer said.