Researchers may have discovered why Covid-19 is so adept at jumping between species, which could help better predict how the virus will evolve.

Early in the pandemic scientists discovered the SARS-Cov-2 virus sweeping the globe infected humans by ‘hijacking’ a receptor on the surface of cells. The ACE2 protein affected is particularly numerous in cells lining the nose and lungs.

However, SARS-Cov-2 has shown the ability to bind with other proteins, prompting a team from the University of Virginia to investigate whether they could infect cells without ACE2 receptors. 

The results showed they could, offering a possible explanation as to how the virus was able to so easily infect other species. Domestic dogs and cats are among the many animals to have contracted the disease, while the virus swept through mink farms in Denmark, resulting in millions of the animals being killed.

Co-author Dr Peter Kasson likened the new pathway to Covid-19 using a back door.

‘The virus that causes Covid-19 uses ACE2 as the front door to infect cells, but we’ve found that if the front door is blocked, it can also use the back door – or the windows,’ he said.

‘This means the virus can keep spreading as it infects a new species until it adapts to use a particular species’ front door. So we have to watch out for new viruses doing the same thing to infect us.’

Covid-19 has killed almost seven million people globally. Cases in both the UK and US have been increasing in recent weeks, and a new strain, Eris, has been labelled a ‘variant of interest’ by the World Health Organization.

How the pandemic began is still a topic of much debate, with most divided into two camps – that the virus was leaked from a large lab in Wuhan, where Covid-19 was first detected, or it was a ‘zoonotic spillover event’, leaping from another animal species to humans at a Wuhan market.

Neither theory has been categorically confirmed, but researchers hope a better understanding of how the virus moves between species will help predict how it evolves in the future, even if it doesn’t answer where the virus originated.

‘Coronaviruses like SARS-CoV-2 have already caused one pandemic and several near misses that we know of,’ said Dr Kasson. ‘That suggests there are more out there, and we need to learn how they spread and what to watch out for.’

The study is published in the journal Chemical Science.

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