First there were sneezing hamsters, now sneezing cats. A team in Thailand reports the first solid evidence of a pet cat infecting a person with SARS-CoV-2 – adding felines to the list of animals that can transmit the virus to humans.
The researchers say the results are compelling. They are surprised that it has taken so long to establish that transmission can occur, given the scale of the pandemic, the ability of the virus to jump from one animal species to another and the close contact between cats and humans. “We knew this was a possibility for two years,” says Angela Bosco-Lauth, an infectious disease researcher at Colorado State University in Fort Collins.
Studies early in the pandemic found that cats shed infectious virus particles and could infect other cats. And during the pandemic, countries have reported SARS-CoV-2 infections in dozens of pet cats. But establishing the direction of viral spread – cat to human or human to cat – is tricky. The Thai study “is an interesting case report and a great example of what good contact tracing can do,” says Marion Koopmans, a virologist at the Erasmus University Medical Center in Rotterdam, the Netherlands.
The feline discovery, published in Emerging infectious diseases on June 6, happened by accident, says co-author Sarunyou Chusri, an infectious disease researcher and physician at Prince of Songkla University in Hat Yai, southern Thailand. In August, a father and son who had tested positive for SARS-CoV-2 were moved to an isolation ward at University Hospital. Their ten-year-old cat was also swabbed and tested positive. While being swabbed, the cat sneezed in front of a vet, who was wearing a mask and gloves but no eye protection.
Three days later, the vet developed fever, sniffles and a cough, and later tested positive for SARS-CoV-2, but none of his close contacts developed COVID-19, suggesting that she had been infected by the cat. Genetic analysis also confirmed that the vet was infected with the same variant as the cat and its owners, and that the viral genomic sequences were identical.
The researchers say such cases of cat-to-human transmission are likely rare. Experimental studies have shown that infected cats do not shed much virus and only shed for a few days, says Leo Poon, a virologist at the University of Hong Kong.
Still, Chusri says it’s worth taking extra precautions when handling cats suspected of being infected. People “shouldn’t give up on their cats, but take better care of them,” he says.
Other animals suspected of infecting humans include farmed mink in Europe and North America, pet hamsters in Hong Kong and wild white-tailed deer in Canada. Adding cats to the list “expands our understanding of the zoonotic potential of this virus,” says Poon.
But the researchers say these are all rare events and animals do not yet play a significant role in spreading the virus. “Humans are clearly still the primary source of the virus,” Bosco-Lauth says.
This article is reproduced with permission and was first published on June 29, 2022.