Why are there so many new Omicron subvariants?

Biology experts Sebastian Duchen and Ash Porter discuss whether the virus is mutating faster and its impact on the future of Covid.

Many of us will now be familiar with the Omicron variant of Sars-CoV-2, the virus that causes Covid.this Variant of concern It changed the course of the pandemic and dramatically increased the number of cases around the world.

We also hear more and more about new Omicron subvariants with names such as BA.2, BA.4, and now BA.5.The concern is that these subvariants can lead to people ReinfectLeads to another rise in the case.

Why are we seeing more of these new subvariants? Is the virus mutating fast? And what are the implications for Covid’s future?

Why are there so many types of Omicrons?

All viruses, including Sars-CoV-2, are constantly mutating. The majority of mutations have little or no effect on the ability of the virus to be transmitted from person to person or to cause serious illness.

When the virus accumulates a significant number of mutations, it Different strains (It’s like another branch of the family tree). However, the strain of the virus is labeled as a mutant until it enhances the ability of the virus to transmit and / or accumulates some unique mutations known to cause more serious disease. It will not be.

This was the case for the BA strain (also known as B.1.1.529) World Health Organization. Labeled Omicron.. Omicron spreads rapidly, Almost everything Current cases where the genome has been sequenced globally.

Omicron spread rapidly and had many opportunities to mutate, so it also acquired its own specific mutation. These gave rise to several sub-strains, or sub-variants.

The first two were labeled BA.1. BA.2.. The current list also includes BA.1.1, BA.3, BA.4, and BA.5.

Subvariants of earlier versions of the virus, such as Delta, were seen. But Omicron defeated them, probably because of their increased transmissibility. Therefore, subvariants of previous virus variants are less common today and less emphasis is placed on tracking them.

Why are subvariants important?

These Omicron subvariants, especially BA.4 and BA.5, Reinfect people With previous infection from BA.1 or other strains. There is also concern that these subvariants can infect vaccinated people.

So we Rapid increase in Covid cases In the coming weeks and months due to the reinfection already seen in South Africa.

but, Recent research A third dose of the Covid vaccine suggests that it is the most effective way to slow the spread of omicrons (including subvariants) and prevent Covid-related hospitalizations.

Recently, BA.2.12.1 has also been attracting attention. It is rapidly becoming popular in the United States and has recently become popular. Australian wastewater.. Surprisingly, if someone becomes infected with Omicron’s subvariant BA.1, it can be re-infected with the next sublineage. BA.2, BA.4 and BA.5 Because it has the ability to avoid an immune response.

Is the virus mutating fast?

I think Sars-CoV-2 is a super fast front runner when it comes to mutations. However, the virus actually mutates relatively slowly. For example, influenza virus. Mutates at least 4 times faster..

However, Sars-CoV-2 has a short-term “mutant sprint”. Our study shows.. In one of these sprints, the virus can mutate four times faster than normal for weeks.

After such a sprint, the strain has more mutations, some of which may be advantageous over other strains. Examples include mutations that help increase the transmission of the virus, cause more serious illnesses, and avoid immune responses. Therefore, new mutants are emerging.

It is unknown why the virus causes a mutant sprint, leading to the emergence of mutants. but, Two main theories About the origin of Omicron and how many mutations it has accumulated.

First, the virus may have evolved with chronic (long-term) infections in people who are immunosuppressed (weakened immune system).

Second, the virus may have “jumped” to another species before it could infect humans again.

What other tricks does the virus have?

Mutations are not the only way in which mutations appear.The Omicron XE variant It appears to be the result of a recombination event. This is where one patient was infected with BA.1 and BA.2 at the same time. This coinfection led to a “genome swap” and a hybrid variant.

Other examples of recombination with Sars-CoV-2 have been reported between Delta and Omicron. Called Deltacron..

So far, the recombinants are more contagious or do not appear to cause more serious consequences. However, this can change rapidly with new recombinants. Therefore, scientists are watching them carefully.

What do you see in the future?

As long as the virus is prevalent, new virus strains and variants can be seen. Since Omicron is currently the most common variant, more subvariants of Omicron, and potentially even recombinant strains, may be found.

Scientists continue to track new mutations and recombination events (especially using subvariants). We also use genomic technology to predict how these will occur and their impact on the behavior of the virus.

This knowledge helps limit the spread and impact of variants and subvariants. It also guides the development of vaccines that are effective against multiple or specific variants.

Sebastian DuchenARC DECRA Fellow, University of MelbourneWhen Ash porter,Researcher, Peter Doherty Institute for Infection and Immunity

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