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Why Omicron is ‘variant of concern’ of Coronavirus?

by Sib Kumar Das

NEWS HIGHLIGHTS

* Omicron is the most heavily mutated variant of COVID-19 causing virus.

* Omicron variant has 50 overall mutations, with 32 mutations in its spike protein alone.

A new variant of Coronavirus named Omicron (B.1.1.529) was first reported by researchers in South Africa on Nov. 24, 2021. Two days later it was termed a ‘variant of concern’ by the World Health Organization (WHO). Now cases of Omicron infection have also emerged in India.

Mutation power:

Omicron is the most heavily mutated variant of COVID-19 causing virus. The Omicron variant has 50 overall mutations, with 32 mutations in its spike protein alone. The spike protein forms the protruding knobs on the outside of the COVID virus. These spikes help the virus to stick to our cells to facilitate its entry.

In comparison, the delta variant of Coronavirus has nine mutations. Larger number of mutations in the Omicron variant increases chances that it can be more transmissible and may be better at evading our immune system. This is a cause of concern.

Spike protein:

Omicron has some mutations similar to the delta variant. But it also possesses other mutations that are totally different. Omicron variant has 10 mutations in the receptor-binding domain or area, the part of the spike protein which mediates entry of the virus into the human cells. In comparison delta variant has just two mutations in the receptor-binding domain.

Reinfection risk:

According to the WHO, preliminary evidences suggest there may be an increased risk of reinfection with Omicron. Persons previously infected by other strains of COVID-19 may get re-infected easily by Omicron variant. It is not yet clear whether infection with Omicron causes more severe disease. Current information does not suggest that symptoms associated with Omicron are different from those from other variants.

Possible origin:

It is suspected that viral variants like Omicron with multiple mutations may have emerged through prolonged infection in a patient whose immune system was suppressed. Such a situation leads to rapid viral evolution. Researchers have hypothesized that some of the earlier SARS-CoV-2 variants like the alpha variant may have emerged started from a persistently infected patient. Unusual pattern and numerous mutations in the Omicron variant make it different from other SARS-CoV-2 strains. No one is sure how these mutations came about. Another possible source of variants could be through animal hosts. It cannot be ruled out that possibly the Omicron variant emerged in an animal host through rapid evolution.