Why coronavirus infects some animals and not others

Coronavirus Infected Swab Test Sample in Doctor Hands. COVID-19 Epidemic and Virus Outbreak.
Certain species of animals have tested positive for the coronavirus, while others appear to have escaped unscathed. (Stock, Getty Images)

Scientists may have uncovered why some animals become infected with the coronavirus, while others appear to be immune to the infection.

The virus is thought to have originated in bats before jumping into humans, possibly via pangolins.

Since the start of the outbreak, dogs, minks and even a New York zoo tiger have tested positive for the infection, while other species appear to have escaped unscathed.

To learn more, scientists from Stanford University in California analysed the “spike” protein on the coronavirus’ surface, which binds to a receptor called ACE2 on the cells of many animals, allowing the virus entry into the body.

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Results suggest the “lock” of certain animals’ ACE2 receptor fits the virus’ “key” better, making these species more susceptible.

The scientists hope their findings will aid the development of antiviral drugs that use artificial “locks” to trap the virus.

Small white pet dog wearing a surgical face mask
A dog in Hong Kong tested 'weak positive' for the coronavirus early in the outbreak. (Stock, Getty Images)

In October, scientists from University College London warned 26 animals “regularly in contact with people” around the world – like sheep and great apes – may be susceptible to the coronavirus.

They concluded most birds, fish and reptiles appear incapable of catching the infection.

To learn more, the Stanford team combined data from previous research into computer models that simulate the spike protein’s structure and investigate how it interacts with different animals’ ACE2 receptors.

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“Thanks to open-access data, preprints and freely available academic software, we went from wondering if tigers could catch COVID-19 to having 3D models of protein structures offering a possible explanation as to why that is the case in just a few weeks,” said lead author João Rodrigues.

Results, published journal PLOS Computational Biology, suggest certain animals are immune to the infection due to their ACE2 receptors lacking the structural features that enable the coronavirus to interact with cells.

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Are animals a risk amid the coronavirus outbreak?

According to the World Health Organization (WHO), the coronavirus spreads between humans.

This mainly occurs when infected droplets are expelled in a cough or sneeze. There is also evidence the virus can survive on surfaces or be transmitted via faeces.

Nevertheless, concerns were raised early in the outbreak when a dog in Hong Kong tested “weak positive” for the coronavirus, however, experts stressed there was “no evidence pet animals can be a source of infection”.

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A tiger in a New York zoo also hit the headlines when it caught the virus, even developing a tell-tale dry cough.

Research has also recently linked the potential transmission from dogs to humans as being behind an “extreme outbreak in North Italy”.

Infections have also emerged on several mink farms worldwide. The coronavirus was thought to have passed from farmers into the animals and then occasionally back into humans.

When it comes to animals catching the coronavirus, experts have previously warned against “mass hysteria”.

When news of the “weak positive” Hong Kong dog broke, Professor Jonathan Ball from the University of Nottingham stressed “we have to differentiate between real infection and just detecting the presence of the virus”.

“The fact the test result was weakly positive would suggest this is environmental contamination or simply the presence of coronavirus shed from human contact that has ended up in the dog’s samples,” he said.

Professor Glenn Browning from the University of Melbourne agreed animal owners should not panic, adding: “People appear to pose more risk to their pets than they do to us.”

The WHO has stressed, however, anyone with confirmed or susceptible coronavirus should “limit contact with companion and other animals”.

“When handling and caring for animals, basic hygiene measures should always be implemented,” it added.

“This includes hand washing after handling animals, their food or supplies, as well as avoiding kissing, licking or sharing food.”

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