UPDATE: On March 12, Hong Kong's Agriculture, Fisheries & Conservation Department released a statement that said a blood test of a 17-year-old dog that was initially found to have a "low-level infection" of the coronavirus through other measures came back negative.

On March 18, it was announced that the dog, which belonged to a patient with COVID-19, had died. Vets in Hong Kong said the stress and anxiety of being in quarantine while under examination may have been a contributing factor. Read more here.

The World Health Organization has said there is no evidence that pets can be infected with the coronavirus that causes COVID-19.

News that a dog tested positive for the coronavirus in Hong Kong likely set off alarm bells this week among pet owners. While there's no indication the virus can spread to humans from dogs, some experts say there may be a need for quarantines among pets of owners who contract the virus.

Hong Kong officials collected samples on Feb. 26 from a dog of a patient who had COVID-19 and found "low levels" of the coronavirus in its nose and mouth the following day.

If you have a dog, cat or ferret, and you're isolating at home, those animals should be isolated at home with you. - Prof. J. Scott Weese, University of Guelph's Ontario Veterinary College

Followup tests determined the dog tested "weak positive" for the virus. Then, international experts at the World Organisation for Animal Health (OIE) concluded the dog has some degree of infection, likely caused by human-to-animal transmission.

"I think this dog has a low level of infection," Thomas Sit, assistant director of the Hong Kong Agriculture, Fisheries & Conservation Department (AFCD), said Thursday.

"According to experts, it's likely the human infected the dog.… Sometimes animals infect humans and sometimes [it's] the other way around."

The dog, which is reportedly a 17-year-old Pomeranian, has been in quarantine in Hong Kong under close surveillance, but has displayed no symptoms of the COVID-19 illness.

How did the dog get infected?

Prof. J. Scott Weese of the University of Guelph's Ontario Veterinary College, who studies diseases that can pass between animals and humans, said it was initially thought the dog became infected due to contamination from living in close contact with its owner.

"The fact that it was positive two days later and they weren't calling it a 'weak positive' the second time would suggest that it was more of a true positive that's more consistent with the dog actually being infected," he said.

"The dog is clinically normal, which is good for the dog, but it also [shows] why we need to sort this out."

Dr. Mike Ryan, director of WHO's emergency program, said it's not unusual to find animals that can be "transient hosts" in infectious disease outbreaks, carrying the disease without spreading it.

He said similar issues have been seen in the SARS epidemic of 2003 and the ongoing MERS outbreaks in the Middle East.

"This dog is a victim..." he said. "We need to establish quite clearly what part animals might play in further transmission, but that is unknown."

A dog wearing a face mask is seen in Shanghai on March 2. (Aly Song/Reuters)

Dr. William Karesh, executive vice-president of the EcoHealth Alliance and a veterinarian based in New York working with the OIE on this case, said it's possible other animals could carry the virus.

At least two cats were found to be carriers of SARS after an outbreak in a Hong Kong apartment complex during the 2003 epidemic.

"They tested positive for SARS because they were living with so many people that were infected," he said.

"But they never transmitted the disease to anyone. There was no evidence that they spread the disease."

Could the dog infect humans or other pets?

The dog will be repeatedly tested over the coming days and Hong Kong officials say it will only be released after it tests negative. Genetic tests are also reportedly being done on the coronavirus taken from the dog, to determine if it mutated after infection.

"We don't have enough data to have a 100 [per cent] answer whether it's infectious to other dogs or not," Sit said.

"But if the dog owner is positive, it's better to take precautionary measures to prevent onward transmission."

A dog wearing a mask is seen in Shanghai on Feb. 16. (Aly Song/Reuters)

The World Small Animal Veterinary Association said in a statement that while tests revealed a small quantity of COVID-19, they did not indicate whether there were "intact virus particles" that are infectious – or just fragments of the genetic material that are not contagious.

"Just like there are different types of people that might be more likely to show clinical disease, the same thing may be true with our animals," said Dr. Jason Stull, a veterinary epidemiologist and assistant professor at the Atlantic Veterinary College at the University of P.E.I.

"We need more information. The fact that Hong Kong has started to do this, I think will be overall helpful and better [for] understanding what the true risk might be."

Should pets of COVID-19 patients be isolated?

Weese said one scenario that needs to be ruled out are "perfectly healthy" animals that show no signs of infection but are still able to shed the virus.

"So even if they can't get infected, we're worried they could track it around," he said.

"That's why I want to get the awareness out that if you have a dog, cat or ferret, and you're isolating at home, those animals should be isolated at home with you."

Hong Kong's AFCD says it "strongly advises" that dogs and cats from the homes of COVID-19 patients be put under quarantine as a precaution, while the World Health Organization says it is monitoring the situation closely.

"We're only aware of this one animal that's tested positive and he's doing well," Dr. Maria Van Kerkhove, an infectious disease epidemiologist with the WHO, said at a news conference Thursday.

"We don't believe that this is a major driver of transmission … but again it's only one example of this and so of course it deserves much more study."

Should Canadian pet owners be concerned?

The Public Health Agency of Canada says there is currently no evidence to suggest that any animal native to Canada (wild, livestock or pets) harbours the virus that causes COVID-19 and animals in Canada don't pose a risk of infecting people with the virus.

The agency recommends that, until we know more, patients infected with COVID-19 and have a pet or other animal should: