A pug in North Carolina named Winston has tested positive for the coronavirus in what is apparently the first known case in which the virus was detected in a dog in the US, researchers at Duke University said on Tuesday.

The dog belongs to a Chapel Hill family participating in a research study at the university, in which researchers were trying to understand how humans respond to different types of infection. Three of the family members, Dr. Heather McLean, Dr Samuel McLean and their son Ben McLean, were also infected by the virus.

The dog’s symptoms lasted only a few days and were mild, according to members of the family — he was sluggish, sneezing and breathing heavily. Most telling of all, they said, he didn’t finish breakfast one morning.

Winston’s preliminary test results, if confirmed by the US agriculture department, will raise broader questions about how susceptible animals are to the coronavirus. Experts have said that there is no evidence that pets can transmit the virus to people, and that people should not worry about giving the virus to their pets.

Dr John Howe, president of the American Veterinary Medical Association, said Winston could have licked something or someone with the virus, causing him to test positive, but that did not mean that the virus was in his bloodstream.