The study, published in the New England Journal of Medicine, however, states that none of the cats showed signs of illness and that the felines ultimately cleared the virus.
Humans remain the biggest risk to other humans in the transmission of the virus. There is no evidence that cats readily transmit the virus to humans, nor are there documented cases in which humans have become ill with Covid-19 because of contact with cats, it states.
Professor of Pathobiological Sciences at the University of Wisconsin School of Veterinary Medicine Yoshihiro Kawaoka led the study, in which researchers administered to three cats SARS-CoV-2 isolated from a human patient.
The following day, the researchers swabbed the nasal passages of the cats and were able to detect the virus in two of the animals. Within three days, they detected the virus in all of the cats. These felines were then placed with other cats each of which shed SARS-CoV-2 from their nasal passages for up to six days.
“That was a major finding for us — the cats did not have symptoms,” says Kawaoka, who also holds a faculty appointment at the University of Tokyo. Kawaoka is also helping lead an effort to create a human Covid-19 vaccine called CoroFlu.
The findings suggest cats may be capable of becoming infected with the virus when exposed to people or other cats positive for SARS-CoV-2. It follows a study published in Science by scientists at the Chinese Academy of Agricultural Sciences that also showed cats (and ferrets) could become infected with and potentially transmit the virus. The virus is known to be transmitted in humans through contact with respiratory droplets and saliva.
“It’s something for people to keep in mind,” says Peter Halfmann, a research professor at UW-Madison who helped lead the study. “If they are quarantined in their house and are worried about passing Covid-19 to children and spouses, they should also worry about giving it to their animals.”
Both researchers advise that people with symptoms of Covid-19 avoid contact with cats. They also advise cat owners to keep their pets indoors, in order to limit the contact their cats have with other people and animals.
If a person is Covid-19 positive, then the person must limit interactions with pets to protect them from exposure to the virus, suggest the researchers.