Within days from scientists' announcement in November 2021 that they had discovered a new worrying variant of COVID-19, the World Health Organization declared that this strain, now called Omicron, was a variant of concern.
According to Medical News Today, they reported that the strain was spreading very fast in southern Africa and had many unusual mutations possible to make the virus more contagious than previous strains.
Verifying the early fears of scientists earlier this month, Omicron was driving an unmatched surge in global cases.
Many of these mutations that health experts have detected in Omicron are rare among formerly sequenced variants of COVID-19.
Essentially, Omicron presents a puzzle for researchers since no known intermediate strains reveal how this new variant evolved. It is nearly as if it appeared out of nowhere.
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Researchers discovered evidence that the new COVID-19 Omicron variant may have evolved its large collection of uncommon mutations in mice.
Alternative Theories for Omicron's Origin
The MNT report also specified substitute theories for the origin of the new Omicron variant. The first theory says that the strain evolved undetected in a "population somewhere in the world" with minimal COVID-19 sequencing and surveillance.
This theory also presents that the virus evolved in a person who remained with the infection for an extraordinarily long time since their immunity was compromised, probably due to a simultaneous HIV infection or treatment with an immune-suppressing medication.
Furthermore, according to a Science report, the strain evolved in an animal population before a person got infected with the virus. The second theory is the most popular for epidemiologists and virologists.
Nonetheless, some experts have debated that other viruses like the influenza virus will become less contagious over time in people who have compromised immune systems.
The scientists also mentioned evidence that whereas such viruses evolve adaptations to the immune system of their host, they amass other mutations making them less able to cause contagions in other people. Nevertheless, Omicron appears to be more contagious than all previously identified strains.
Unusual Mutations in Mice
The Beijing-based Chinese Academy of Sciences in Beijing has now discovered evidence that this new COVID-19 variant may have evolved its large collection of uncommon mutations in mice.
The researchers believe that an earlier strain from the lineage identified as B.1.1 jumped from a human into a mouse in the middle of 2020.
Over time it evolved a range of reworking to its new host before it caused an infection in another human late last year.
They were able to identify more than 40 point mutations in the Omicron variant's RNA that they suggest took place after the strain split from its last known common descendants in humans.
RNA Viruses Tend to Pick-Up More Mutations
Essentially, point mutations are alternatives of single chemical letters identified bases in the four-letter genetic code.
Previous research proposes RNA viruses are inclined to pick up more mutations in certain bases, according to which animal host they replicate inside.
With this knowledge, researchers of the new study have formerly identified the mutation "signature" of various animal hosts of the COVID-19 infection.
Omicron Evolved in Mice, Rather than Humans
The new study published in the Journal of Genetics and Genomics showed that the relative frequency of the new point mutations in the new Omicron variant is characteristic of evolution in a mouse host instead of a human host.
The researchers found that the Omicron strain's mutation signature differs from numerous variants known to have evolved in humans, including three variants isolated from patients infected with chronic COVID-19.
Moreover, the scientists also discovered that several mutations in the spike protein of Omicron, which SARS-CoV-2 uses to cause infection in host cells, help bind it more tightly to its aim receptor in mice.
Related information about Omicron variant coming from mice is shown on Dr. John Campbell's YouTube video below:
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