(CNN)A North Carolina family's pug may be the first dog in the United States to test positive for coronavirus, according to researchers.
Three members of the McLean family -- Sam McLean, wife Heather and their son, Ben -- contracted Covid-19 last month. Sydney McLean, the couple's daughter, was the only family member to never show any symptoms.
The family found out their dog, Winston, tested positive for the virus too after they participated in a Duke University study about Covid-19 aimed at trying to find potential treatments and vaccines. As part of the study, members of the family under go weekly nasal swabs and give blood samples.
Chris Woods, the principal investigator of the study, said researchers have also been collecting samples from family pets to see how coronavirus spreads in households. Researchers did not use the commercial tests that are in high demand around the world to test the animals.
Although they haven't tested many pets, Winston's sample is the only one that's come back positive. He is believed to be the first dog in the country to test positive for the virus, according to the university.
"His (Winston's) amount of virus that we detected was very low, suggesting that he would not be a likely mechanism or vector of transmission of virus to either other animals or to, to humans in these households," Woods said.
Sam McLean, a researcher and emergency room doctor at the University of North Carolina at Chapel Hill, was the first member of the family to get sick, his wife Heather McLean said. He had treated Covid-19 patients before he got sick.
Winston did show some minor symptoms while his family was also sick.
"He had a small cough for a day or two right in the peak when all of us were sick and he didn't eat his breakfast one morning," Ben McLean told CNN. "But we didn't have any concrete, like, super alarming illnesses where we're like, 'we need to take him to the vet. He's like really sick.'"
Woods said researchers don't know if coronavirus made Winston sick, or if he had an unrelated ailment.
The McLeans have another dog and a cat, whose tests were negative.
Winston tends to lick things and likes to spend more time around his family, Heather McLean said. Their cat is more aloof, and their older pug likes to sleep most of the time.
"Winston is much more affectionate and we hold them all the time," she told CNN. "So if any of the animals were to have a positive viral test, it would be him."
Federal officials announced last week that two cats tested positive for the novel coronavirus in New York.
Eight lions and tigers tested positive for Covid-19 at the Bronx Zoo, but the big cats are all doing well, according to a news release.
Two dogs under quarantine in Hong Kong also tested positive for the virus, according to officials there.