A veterinarian in Thailand may have been infected with the coronavirus from an infected pet cat last year, researchers have concluded in a new study. This is the first recorded case of suspected cat-to-human transmission, although experts stress that cats have an overall lower risk of infecting humans with the virus.
One of the two cat owners, both of whom had Kovid-19, probably spread the virus to the cat, which then sneezed into the veterinarian’s mouth, according to the paper, which was written by scientists at the Prince of Songla University in Thailand. Genomic sequencing confirmed that cats and all three humans were infected with a single version of the virus, which was not widespread among the local population at the time.
Cats are far more likely to spread the virus from humans, scientists say. But the incident is a reminder that people infected with the virus should be careful around their pets – and veterinarians and shelter workers who may come in contact with infected animals should do the same, says Dr. Scott Weiss, a veterinarian with an infectious disease. At Guelph University in Ontario.
“When things turn into human diseases, we too often forget everything else,” he said. “I think it’s important for us to identify if this virus can still transmit between species.”
Previous research has shown that pet owners can infect their cats and that in certain situations cats can transmit the virus to each other. But it is difficult to prove that human transmission from cats occurs in natural settings. (Mink, hamster and deer have been reported to spread the virus among humans.)
The new paper was published this week in the Emerging Infectious Diseases Journal, published by the US Center for Disease Control and Prevention. This makes it a powerful case for the transmission from cats to humans, Dr. Weiss says: “They have a beautiful story here.”
On August 4, Bangkok, a father and son, developed symptoms of Covid-19 and subsequently tested positive for the virus. Due to a shortage of hospital beds in Bangkok, the two were taken on August 8 by a 20-hour ambulance ride to a hospital in Songkhla, a province in southern Thailand. For whatever reason, they have brought their pet cats.
When the men were admitted to the hospital, the cat was sent to a veterinary hospital for examination. Although the cat appeared to be healthy, the veterinarian, a 32-year-old woman, collected nasal and rectal swabs, which tested positive for the virus. While the vet was blowing the cat’s nose, the animal sneezed in his mouth. (The veterinarian wore gloves and a mask during the test, but did not have a face mask or eye protection.)
On August 13, the veterinarian developed Covid-19 symptoms, including a fever and a cough. Shortly thereafter, he tested positive for the virus.
Genomic sequencing revealed that cat owners, cats and veterinarians were all infected with the same version of the Delta variant, which was different from the viral samples taken from other patients in Songkhla at the time.
The PCR test suggested that the cat had a high viral load during the veterinary test. None of the veterinarian’s close acquaintances were known to have Covid-19 at the time, and he had no previous encounters with pet owners, adding to the theory that the cat was the source of the veterinarian’s infection. (It was not clear if he later met with the owners.)
The CDC recommends that people infected with the virus avoid contact with their pets. “If you’re trying to stay away from people because you’re potentially contagious,” says Dr. Weiss, “just try to stay away from animals at the same time.”