The Animal Humane Society closed all three of its Twin Cities shelters Thursday and paused pet adoptions for at least a month due to a suspected outbreak of canine influenza — a highly contagious virus that's rarely been reported before in Minnesota.

If confirmed, it will be the largest outbreak ever of canine influenza in Minnesota as cases of the respiratory infection surge in other states across the country.

"Unfortunately we just have to ride it out ... giving animals time in quarantine to rest, recuperate," said Sara Lewis, the Humane Society's managing shelter veterinarian.

A dog transported from Oklahoma had been exposed to the virus March 23. Since then, all of the approximately 200 dogs at the Humane Society's shelters in Golden Valley, Woodbury and Coon Rapids have contracted respiratory infections.

All dogs will be tested, and while none have tested positive yet for canine influenza, Lewis said they suspect it's the illness based on the dogs' symptoms, which are like flu symptoms in humans, including coughing and sneezing.

The Minnesota Board of Animal Health immediately issued a quarantine of all dogs at the Animal Humane Society's shelters, suggesting a 42-day quarantine, said Michael Crusan, spokesman for the state agency.

Dogs are sick and contagious for three to four weeks, so Humane Society officials said they're planning to keep the three adoption centers closed for at least 21 days. It will be the longest closure ever for an animal-related outbreak at the organization, which shuttered for six weeks in 2020 to prevent the spread of COVID-19 among employees.

The first outbreak of canine influenza was detected in the U.S. in 2015, but the only reported outbreak of the virus in Minnesota was in 2017 when 13 dogs were infected, said Veronica Bartsch, senior veterinarian with the Board of Animal Health.

She said southern states like Texas have reported more cases of canine influenza likely because they have more stray dogs and densely populated dog shelters than Minnesota. While dog shelters in other states frequently vaccinate dogs for canine flu, the Humane Society hadn't done so because the illness was so rare in Minnesota, Lewis said, adding that they'll vaccinate dogs for canine influenza going forward.

"Now that we've seen it in Minnesota, we know it can come anywhere," she said. "We're just treating it as something that is now going to be here."

Canine influenza isn't transmittable to humans or most other animals, but it is more serious than kennel cough, a respiratory disease dogs can get that's akin to a mild cold. Canine influenza can cause higher fevers, more coughing and possibly morph into severe pneumonia, Bartsch said. She recommends that dog owners monitor their pets and discuss with their veterinarian whether to vaccinate their pup.

She said dogs, like humans, are more likely to get respiratory illnesses when congregating indoors, and dog owners should be aware of that risk with dog boarding, day care facilities or other indoor group settings.

Lewis said a majority of the dogs at the Humane Society are likely to recover and the organization is alerting anyone who adopted a dog since March 23 about the possibility of the illness.

At the nonprofit's Golden Valley adoption center, visitors showing up to adopt a pet were turned away Thursday. The pause on adoptions also means the nonprofit won't be able to accept new dogs to its shelters. But leaders said they hope the closures will stem the spread of the virus in the state.

"We're doing this not just to protect and take care of the animals that are here, but obviously to protect and care for the animals that are in our community, knowing this is a community that has a lot of dogs," said Lisa Baumgartner Bonds, the nonprofit's chief advancement officer. "We don't want this to go beyond us."