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Omicron is unique in that it is the most severely mutated type of SARS-CoV-2, the virus that causes COVID-19, that has ever been discovered. There are 50 mutations in the omicron variation in total, with 32 mutations in the spike protein alone. The spike protein on the exterior of the SARS-CoV-2 virus, which creates projecting knobs, aids the virus’s ability to cling to cells and obtain access.
It’s also the protein that induces protective antibodies in all three vaccines now available in the US. The delta version features nine alterations, for comparison. Because the omicron form has a higher number of mutations, it may be more transmissible and/or better at evading immune defences, which is a highly troubling possibility.
I’m a virologist who researches emerging and zoonotic viruses to learn more about how new epidemic or pandemic viruses originate. My research group has been looking into many elements of the COVID-19 virus, such as its animal spread.
Why are there so many new SARS-CoV-2 variants?
While the omicron variety’s extraordinarily large number of mutations is unexpected, the appearance of yet another SARS-CoV-2 variation is not.
Random mutations accumulate in all viruses through natural selection. RNA viruses, such as SARS-CoV-2, have this process accelerated. If and when a set of mutations gives a variant an edge over its predecessors in terms of survival, the variant will outcompete all other virus variants.
Is the fact that the omicron variation has more mutations than the delta variant a sign that it’s more harmful and transmissible? Simply said, we don’t know. The circumstances leading to the formation of the variation are unknown, however the sheer number and arrangement of mutations in omicron are remarkable.
Long-term infection in a patient with a weakened immune system, a circumstance that might contribute to rapid viral evolution, is one possible explanation for how viral variants with numerous mutations originate. Some of the earliest SARS-CoV-2 varieties, such as the alpha variant, are thought to have originated from a persistently infected patient, according to researchers. The omicron variety, on the other hand, is distinct from all other SARS-CoV-2 strains due to its odd mutation pattern and many mutations, raising issues regarding how it emerged.
Animal hosts could be another potential source of variations. COVID-19 is spread by a virus that can infect a variety of animals, including mink, tigers, lions, cats, and dogs.
An international team led by me recently revealed extensive infection by SARS-CoV-2 in free-living and captive white-tailed deer in the United States in a study that has not yet been peer-reviewed. As a result, we can’t rule out the likelihood that the omicron variation arose spontaneously in an animal host.
How did the delta variation become the most common in the world?
Delta is 40-60% more transmissible than alpha and approximately twice as transmissible as the original SARS-CoV-2 virus discovered in China. Researchers believe the delta variant’s increased transmissibility is the main reason it was able to outcompete other variants to become the dominant strain.
The replication rate of a virus, or how quickly it can replicate itself, is a significant element in viral fitness. The delta version multiplies 1,000 times quicker than prior SARS-CoV-2 variations, according to an unpublished study.
In addition, those infected with the delta form produce and shed more virus, which could explain its greater propensity to spread. According to research, changes in the spike protein may have resulted in more efficient binding of the spike protein to its host via the ACE-2 receptor, which could explain the delta variant’s increased ability to reproduce.
People infected with the delta version are also more likely to be hospitalised than those infected with the original SARS-CoV-2 or early variations, according to studies. The delta variant’s greater capacity to infiltrate cells and produce more severe disease is considered to be due to a mutation on the spike protein called the P681R mutation.
Will omicron succeed in displacing delta?
It’s too soon to judge whether the omicron variant is more fit than the delta variant or whether it will become dominant. Omicron has several mutations in common with the delta variation, but it also has some that are unique. But one of the reasons why researchers are concerned is that the omicron form has ten mutations in the receptor-binding domain, the region of the spike protein that interacts with the ACE-2 receptor and mediates cell entrance, compared to only two in the delta variant.
Assume that the combination of all of omicron’s mutations makes it more transmissible or better at immune evasion than delta. In that situation, we might observe a global proliferation of this variety. However, it’s possible that the virus’s exceptionally large number of mutations will harm it and render it unstable.
The process of viral adaptability never ends, as we know from influenza viruses. Because many nations have low vaccination rates, the virus will continue to circulate and mutate as long as it can. The appearance of the omicron form serves as a further reminder of the need to vaccinate in order to prevent SARS-CoV-2 from spreading and evolving.
