Mysterious dog respiratory illness spreads in US

By Helena Kiannejad

3 min read

Photo from Alvan Nee

This mysterious illness could be a new type of bacterial infection. It starts in dogs with a cough that won't go away with a runny nose and sneezing. The illness doesn’t respond to standard procedures such as antibiotics. It then develops into pneumonia after just 1-3 weeks and in some cases if left untreated the dog can die. Cases have been reported in Colorado, Oregan, Idaho, Washington, California, Illinois, and more states.

Researchers at the University of New Hampshire’s Veterinary Diagnosis Laboratory and the Hubbard Center for Genome Studies told NBC News they have identified a pathogen that might be what’s making pets sick through a genetic sequencing of samples from 30 dogs from New Hampshire who were infected last year plus 40 from Rhode Island and Massachusetts who got sick this year. The unknown germ has been discovered and is a weird bacterium; it’s smaller than a normal bacterium and was previously unknown. It’s tough to find and sequence because of its small size and genome makeup. However, the illness is still largely unknown, and scientists aren't even sure it’s the same bug making dogs sick across the US. But it’s possible the New Hampshire researchers are correct.

Researchers are still wondering whether it’s a bacteria or viral pathogen. Mike Stepien, a spokesperson for the USDA Animal and Plant Health Inspection Service (APHIS), has said that the illness sometimes causes death in dogs and if not, then severe symptoms. Since there’s no test for the mysterious illness yet and it has many of the same symptoms as other respiratory system infections such as kennel cough and canine influenza, it’s hard to pin down the number of cases so far, but it’s likely somewhere in the thousands in each state it’s been identified in. Those with dogs who caught the illness have said it’s a cough that suddenly out of nowhere turns into pneumonia and their dog had to stay in the ER overnight for 2-5 days, in some cases passing away.

If your dog has a cough that won’t leave after a week or two and other respiratory symptoms, it’s recommended that you contact a veterinarian. To prevent your dog’s chances of contracting this illness experts recommend that you keep your dog out of kennels and other areas such as dog parks, since this is where infection is more likely because of crowded conditions and close contact.

Carroll, Linda. “What to Know on the Mystery Dog Respiratory Illness: Signs, Symptoms and More.” NBC News, NBC News, 21 Nov. 2023,

Hohman, Maura. “Possible Cause of Mystery Dog Illness Identified by Research Lab: What to Know.”, 21 Nov. 2023, Accessed 23 Nov. 2023.

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