First reported case of Covid-19 transmitted from cats to humans

So far, only two species have been known capable of transmitting the COVID-19 virus to humans. The mink and the hamster. The first undoubtedly contributed to spreading the virus among mink farmers. Especially in the Netherlands and Denmark. A situation that led to the slaughter of several million animals. Pet hamsters are suspected to have triggered an outbreak of the Delta variant of SARS-CoV-2 in Hong Kong earlier this year. It is now the cat that finds itself in the crosshairs of the health authorities. Indeed, a Thai veterinarian has tested positive for COVID-19 after one of her “patients” sneezed in her face.

Several animals infected with Covid-19 around the world

As this report from the World Organization for Animal Health, dated August 2021, points out, several countries have already reported cases of COVID-19 in various animal species, including mink, cats, dogs, tigers and lions (in descending order of incidence). In particular, OMSA reports more than a hundred cases involving cats.

However, apart from mink, most of these infections resulted from human-to-animal transmission of the virus (known as reverse zoonosis). For the first time, scientists report suspected zoonotic transmission of SARS-CoV-2 from a cat to a human. Their study appeared in the journal Emerging Infectious Diseasespublished by the Centers for Disease Control and Prevention.

Timeline of the potential first cat-to-human transmission of COVID-19, which occurred in Thailand in August 2021.

On August 15, 2021, in Songkhla, a province in southern Thailand, a 32-year-old, previously healthy veterinarian who lived alone went to the hospital; she had a fever, a clear runny nose and a productive cough for two days. Asked about her background, she told doctors that five days earlier she and two colleagues had examined a cat belonging to a man and his son.

Father and son had both tested positive for SARS-CoV-2, then moved to an isolation ward at the university hospital. Their ten-year-old cat also tested positive. However, during the sample, while the other two veterinarians were holding it, the cat sneezed in front of the veterinarian who carried out the PCR test; she wore a mask and gloves, but no goggles.

Transmission confirmed by genomic sequencing

The veterinarian has tested positive for SARS-CoV-2! However, none of her close contacts (including the other two vets who assisted her) contracted COVID-19. Which suggests that she had been infected by the cat. A genetic study has confirmed this hypothesis! The viral genomic sequences were identical, indicating that the veterinarian was infected with the same variant as the cat and its owners. In addition, the identified genome was distinct from that of other patients from the same province.

The identical genomic sequences of SARS-CoV-2 obtained from the patient and the sequences derived from the cat and its two owners, as well as the temporal overlap of animal and human infections, indicated that their infections were epidemiologically linked. “.

Contact tracing of the 30 staff working at the veterinary hospital identified one additional case of COVID-19. A veterinarian who worked in another service. However, this patient was not involved in the case considered here. Because he had a fever onset 24 hours before the cat’s arrival and had no direct or indirect contact with the cat, its owners or its colleague. Also, its viral genome was different.

Read also: Covid contagion: why does the vaccine not prevent contamination?

A route of contamination that remains anecdotal

It was already known that cats could be infected with SARS-CoV-2 during close contact with their owner – especially if the latter has a symptomatic infection. A study published in 2020 in Science showed that cats are susceptible to airborne transmission. It also showed that their incubation and contagion period are relatively short. Researchers believe this cat likely contracted COVID-19 a week or less before passing it on to the vet.

The meeting with the cat only lasted about ten minutes. But the vet was very close to him. And the viral load of the animal was particularly high at that time, specify the authors of the study. His ocular surface was exposed and therefore vulnerable to infection! Since the patient was equipped with gloves and washed her hands before and after examining the cat, the hypothesis of contamination by direct or indirect contact (via contaminated surfaces for example) was judged less likely.

This study provides evidence that the SARS-CoV-2 virus can be transmitted from cats to humans. But the experts want to be reassuring. This mode of transmission is relatively rare, due to the short period during which cats can shed viral particles. This period is estimated at 5 days on average. To date, animals do not play a significant role in the spread of the virus. Humans remain the main source of the virus. They recommend, however, that people with COVID-19 (suspected or confirmed) refrain from contact with their cat.

Read also: Here’s how SARS-CoV-2 creates ‘ghost ships’ in the brain


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