Veterinarians in the Willamette Valley say they’re seeing an increase in dogs sickened with an unknown respiratory illness.

Very little is known about the mysterious disease that may have infected hundreds of dogs in the region since August. The Oregon Department of Agriculture has received 200 written reports from veterinarians so far. It’s unclear if the disease has impacted dogs outside the valley or outside the state.

In a notification sent to veterinarians, the agriculture department said dogs with the disease develop chronic tracheobronchitis or pneumonia. Some dogs developed acute pneumonia that killed them within two days.

“Unfortunately, very few of those dogs have received a full necropsy to determine the cause of death,” Andrea Cantu-Schomus, a state agriculture spokesperson, said in an emailed statement.

Cantu-Schomus said that of the few dogs that have been studied “several had underlying disease processes that ultimately lead to death.”

Most antibiotics that usually treat canine respiratory illnesses aren’t effective against this disease. Since researchers haven’t yet identified its underlying cause, they haven’t been able to pinpoint ways to treat it, Cantu-Schomus said.

There is no evidence to suggest that human illnesses are associated with this disease, nor is it related to COVID-19, according to the agriculture department.

Most dogs have already gone through a contagious “virus shedding” phase — thus spreading it to other animals — by the time they are seen by veterinarians. The state has partnered with several emergency veterinary practices to begin widespread PCR testing on dogs to test for respiratory illnesses in order to catch it before they start showing symptoms.

The department is also working with pathologists and virologists from state and federal veterinary laboratories as well as the Oregon Veterinary Diagnostic Laboratory at Oregon State University to determine what could be causing the illness

Kurt Williams, the laboratory director at OSU, said too little is known about the disease to advise dog owners on how to avoid it. Canine respiratory diseases like kennel cough are common, and many dogs can recover if they are fully vaccinated.

“[Dog owners] need to make sure their dog is vaccinated for all sorts of canine pathogens, stay attuned to how their dog is behaving, and reach out to their veterinarian,” he said.

Williams’s team isn’t yet sure if the disease is caused by a virus or bacteria, or even if it is a type of infection. His team has sent samples to the U.S. Department of Agriculture for additional genome sequencing, a process of studying an organism’s unique DNA fingerprint. The information could help determine the disease’s underlying cause.

Like Williams, the agriculture department recommends pet owners consult with their veterinarians if they are concerned.

“Because of the broad spectrum of potential respiratory diseases, there is no one-size-fits-all recommendation, and working with a veterinarian is the best way to ensure that owners have accurate information that is appropriate for their situation,” Cantu-Schomus said.