Experts Identify ‘Mysterious’ Illness Affecting Dogs

Reports suggest that more than 20 dogs have died thus far.

Published Aug 24, 2022

Close up of a vet having a check up on a dog (Getty Images/Stock Photo)
Close up of a vet having a check up on a dog (Image Via Getty Images/Stock Photo)

Answers are coming in for questions regarding reports of a “mysterious” illness spreading among canines in parts of Michigan that has resulted in the deaths of at least 20 dogs. Five days after the illness was first reported on Aug. 19, 2022, veterinarian experts have confirmed that the disease is, in fact, canine parvovirus (CPV).

Michigan Department of Agriculture and Rural Development (MDARD) and its partners have confirmed through additional testing that the dogs were infected with CPV after initial point-of-care tests in clinics and shelters came back negative.

“Canine parvovirus is a severe and highly contagious disease in dogs and veterinary professionals have extensive experience with this virus," said State Veterinarian Nora Wineland in a news release.

“We have a highly effective vaccine available to help protect dogs from the virus. Dogs that are not fully vaccinated against this virus are the most at risk. Dog owners across Michigan must work closely with their veterinarians to ensure their dogs are appropriately vaccinated and given timely boosters to keep their pets safe and healthy. Protecting Michigan’s dogs is a team effort.”

What was previously deemed as a “parvo-like” condition has killed more than 20 dogs in Ostego County, Michigan, alone, according to an area animal shelter. At the time of this writing, the total number of dogs affected has not been released to the public.

“This situation is complex because although the dogs displayed clinical signs suggestive of parvovirus, they consistently test negative by point-of-care tests performed in clinics and shelters,” said Michigan State University Veterinary Diagnostic Laboratory (MSU VDL)
Director Kim Dodd.

“Screening tests for parvo are done to help guide immediate isolation, disinfection, and treatment protocols. While those tests are valuable in the clinical setting, they are not as sensitive as the diagnostic tests we can perform here in the laboratory. We continue to further characterize the virus in hopes of better understanding why those animals were testing negative on screening tests.”

As experts continue to gather information about the canine disease spreading across the Great Lakes State, Snopes has put together a quick-hit list at what we know so far.

Experts Confirm the Disease Is Caused by Canine Parvovirus (CPV)

CPV is a highly contagious virus that can infect any dog, but most often causes acute gastrointestinal illness in puppies between 6 and 20 weeks old. Older dogs can also be infected, and a rare variant can be seen in very young puppies that can cause myocarditis, notes Cornell College of Veterinary Medicine.

The virus was first detected in Europe in 1976 and quickly spread around the world before a vaccine was developed in the late 1970s. Despite the highly effective vaccine, which is recommended to all dogs, outbreaks can still occur.

After infection, incubation occurs between three and seven days before symptoms begin. Symptoms include bloody diarrhea, vomiting, lethargy, and loss of appetite. The virus is not contagious to humans, but it can be spread to wild canines, like coyotes and wolves, as well as to foxes and raccoons.

CPV is diagnosed through fecal tests and treatment often requires a hospital stay with an intravenous drip. Antibiotics may also be necessary.

It’s Not Yet Known Why the 2022 Outbreak Wasn’t Initially Detected

As we stated above, initial tests given to dogs at veterinarian clinics and shelters were negative for CPV. However, additional testing from MDARD and MSU VDL revealed the virus to be parvovirus. At the time of this publication, it is not yet known why the virus was not initially detected or if it represents a new variant of the virus. Veterinary experts are continuing to investigate the outbreak and its causes.

Most Cases Occur in Elderly Dogs and Those Under Two Years

Like parvovirus, preliminary reports suggest infection is most often seen in dogs and puppies under the age of 2, and elderly dogs.

Infection Is Not Contained in One Location

As of this publication, the illness was said to have been reported in many counties around northern and central Michigan. It is unclear if the virus has spread across state boundaries.

The Best Defense Is Proper Vaccination

Experts say that nearly all of the infected dogs were unvaccinated, and the best way to prevent against infection is to ensure that your dog is up to date on his immunization.

“We have not seen any dogs die that are properly vaccinated,” wrote the Otsego County Animal Shelter on Facebook. “If you do not know if your dog is properly vaccinated or what properly vaccinated is, contact your veterinarian.”

Puppies and dogs should follow a standardized immunization routine, which includes vaccinations against parvovirus, and also rabies, canine distemper, adenovirus, parainfluenza, and leptospirosis, notes the American Society for the Prevention of Cruelty to Animals.

If a dog comes down with symptoms, isolate the animal and contact your vet immediately. Dogs and puppies should be fully vaccinated before interacting with other animals. Be sure to clean up after your pet when walking out in public.


“Canine Parvovirus.” Cornell University College of Veterinary Medicine, 5 Dec. 2017,

Facebook, Accessed 24 Aug. 2022.

MDARD Encourages Owners to Protect Their Dogs and Puppies through Vaccinations. Accessed 24 Aug. 2022.

Mysterious Parvovirus-like Illness Infecting Dogs in Michigan, Killing as Many as 60 Dogs. Accessed 24 Aug. 2022.

“Parvo-like Illness Reported in Northern Michigan Dogs: Updates.” The College of Veterinary Medicine at Michigan State University, Accessed 24 Aug. 2022.

The College of Veterinary Medicine at Michigan State University, Accessed 24 Aug. 2022.

Update from State Vet. Accessed 24 Aug. 2022.

“Vaccinations for Your Pet.” ASPCA, Accessed 24 Aug. 2022.

Madison Dapcevich is a freelance contributor for Snopes.

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