Omicron could have originated in mice, study reveals


A study has revealed that omicron could have originated in mice, mutating as it spread through the species before it was passed back to humans again.
A recent study performed at the National Institute for Communicable Disease Control and Prevention in China seems to back the theory that an animal, specifically mice, could have been the origin of the omicron variant of coronavirus.
In November 2021, the World Health Organisation (WHO) gave the new variant the name of omicron and classed it as the world’s fifth significant variant of the pandemic. The rapid spread and global dominance of omicron have made scientists anxious to learn more about the variant and its origins.
Although scientists were able to determine that omicron developed from a variant of the virus that was circulating in mid-2020, they could not find any intermediate version that would have immediately preceded omicron. One theory is that omicron infected an animal, allowing mutations to develop as the virus spread through the animal population, before being passed back to humans again.
The investigation, led by Jianguo Xu and published in the Journal of Biosafety and Biosecurity, discovered that the most likely intermediate host animal was a mouse. According to Professor Xu, even though much more work is needed before the theory can be confirmed, “the study calculated the average number of mutations in the five important variants and investigated the key mutations in the viral S protein, where the infection originates”. They found that the omicron variant contains mutations at five key points in the protein: K417, E484, Q493, Q498 and N501.
“This mutation profile shows that the virus has adapted to infect cells in mice,” said Xu. “Omicron could have evolved in a non-human animal species. We believe that coronavirus accumulated mutations slowly over time in mice before it was transmitted to humans by reverse zoonosis,” he added.
These findings suggest that the researchers will now need to focus on isolated variants of coronavirus from wild animals, especially rodents. “If it is confirmed that omicron originated in mice, the implications of its circulation among non-human hosts will give rise to new challenges in the prevention and control of the epidemic,” he concluded.
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Tamsin Brown

Originally from London, Tamsin is based in Malaga and is a local reporter for the Euro Weekly News covering Spanish and international news. Got a news story you want to share? Then get in touch at

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