A dog adopted earlier this week from a St. Paul animal shelter potentially has come down with canine flu, Animal Humane Society officials announced Thursday.

Test results from the dog, a Shar-Pei mix, came back positive for the H3N2 flu even though it showed no signs of illness before being adopted Sunday from the humane society’s St. Paul shelter.

It’s the first reported case of dog flu in the Twin Cities metro area, said Janelle Dixon, president and CEO of the local Animal Humane Society. Nasal swab testing was being done to confirm the diagnosis.

Dixon, speaking at an afternoon news conference, said a second dog diagnosed with pneumonia also is undergoing treatment and is being tested for canine influenza.

“We’re watching closely,” she said.

The shelter dog that fell ill — a male known as Toga during its time at the shelter — “has recovered well and is at home” with its adoptive family, Dixon said.

As a precaution, the humane society isolated all dogs at the St. Paul shelter with kennel cough or similar symptoms and is testing them, too, for the flu — with results expected by 4 p.m. Friday, officials said.

Canine flu was first confirmed in Minnesota in late May, when five dogs contracted it at a training and rescue facility in Detroit Lakes. Fatalities are unlikely, but the flu produces moderate symptoms that can affect a dog for up to two weeks. It doesn’t sicken people, nor is it related to avian flu.

Toga was taken June 2 to the humane society shelter at Como Park by St. Paul Animal Control. The day after it was adopted, it developed flu symptoms, which were described Thursday as a deep-chested cough, nasal discharge and fever.

Dr. Graham Brayshaw, director of animal services for the humane society, said that the dog had no nose-to-nose contact with other dogs at the shelter, raising hopes that it failed to pass along the flu to others.

But no dogs are being accepted or adopted at the shelter until officials can confirm that no other animals are infected.

The humane society also is sending letters to families that adopted dogs from the shelter during the last 30 days urging them to contact their veterinarians if flu symptoms develop.

The news conference was called on the same day that results of Toga’s blood test were reported to the humane society by the Board of Animal Health. But no one at the shelter expressed any alarm.

When asked what the development could mean for dog owners interested in taking their pets to the dog park, Dixon said simply: “This should not mean anything.”