As the news of a Covid resurgence in China makes news, people are googling to see what variant is spreading in the country, and whether it has been found in India yet too. According to reports, the BF.7 Omicron variant – a highly transmissible one – is the dominant strain being seen amid the infection surge in China.
It has been three years to the pandemic and so many strains have been witnessed – XBB, Delta, Omicron etc. But what is a virus variant and how is it formed? We explain:
What is a Variant
We’ve all become familiar with virus mutations during the pandemic, and we can probably all name the COVID variants Alpha, Delta, and Omicron. But as Omicron mutates into Omicron BA.2, Omicron BA.4, Omicron XE, and others, we’re hearing more and more about subvariants.
We know the virus mutates as it spreads, but when is a new mutation considered a new variant and when is it considered a subvariant? What happens when they come together?
To begin, what exactly are mutations?
When cells replicate, they follow a set of genetic instructions (made of DNA or RNA). However, because this is happening at such a rapid pace, errors can occur.
These mistakes, or changes in the genetic code, are referred to as mutations.
We are pretty good at detecting and correcting errors in complex organisms like humans. When these processes of discovery and repair fail, diseases such as cancer emerge.
When errors occur during the copying of genetic material in viruses, the majority of them leave the genetic material too broken to continue replicating, and the virus dies.
Occasionally, by chance, these errors can occur in a section of the code that allows the virus to survive, causing changes in the virus.
How Does a Variant Change Covid’s Behavior?
When it is in a part of the virus that determines how it behaves, it has the ability to change the virus’s properties.
It may alter the severity of the disease it causes, our ability to diagnose the virus using current tests, or even the efficacy of treatments.
COVID has been reported in over millions of cases worldwide since it was first reported in the Chinese city of Wuhan in December 2019. (and probably many more unrecorded cases). That’s a lot of virus replication and a lot of chances for these kinds of changes to happen.
One of the reasons we’ve heard so much about these kinds of changes is our ability to use genomic sequencing to determine the virus’s genetic code. This has enabled us to detect even minor changes in the virus’s 30,000-letter code in real time, a report by the Conversation explains.
When these changes are discovered, the new virus can be described in a variety of ways, mostly based on how different the genetic code and resulting virus properties are from the parent virus from which it arose.
Some terms essentially mean the same thing and can be used interchangeably depending on the industry. While there are many commonly used agreed terms, there are no simple universal definitions.
Is a Variant Different from a Strain?
A variant is a change in the genetic code caused by a mutation or a series of mutations. A variant, while genetically distinct, does not always behave differently than the parent virus.
COVID is caused by a single species of coronavirus known as SARS-CoV-2. Many other viruses (and other organisms) have multiple “strains” with very significant changes not only in the genetic code, but also in the virus’s biological properties and behaviour. Similarly, all dogs are the same species, but they come in a variety of breeds that look and act very differently.
According to some researchers, there has yet to be discovered a type of SARS-CoV-2 that differs sufficiently to meet this definition, so there is only one strain for the time being.
Other researchers, however, have suggested that the variants with different behaviours meet the definition of being different strains.
Others argue that a new variant that becomes dominant in a population earns the title of strain.
What about ‘interest’ and ‘concern’ variants?
A variety of different types of variants have been described to describe the impact of genetic changes on virus behaviour.
In late 2020, the World Health Organization (WHO) classified “variants of interest” and “variants of concern” in collaboration with expert networks, in response to the emergence of variants that posed an increased risk.
A “variant of interest,” according to these WHO definitions, is a variant with genetic changes that are known or predicted to affect important virus characteristics. These include transmissibility, disease severity, immune response protection, reduced ability to detect with diagnostic tests, and reduced treatment effect.
A new variant must also have been identified to cause significant transmission and be thought to pose an emerging risk to public health in order to become a variant of concern.
Basically, once the potential concerning property that made it a variant of interest has been found to be the case, a variant of interest will then become known as a “variant of concern”.
What exactly are subvariants?
Because Omicron has been shown to be more infectious than its predecessors, it has spread rapidly around the world. Omicron has had the opportunity to acquire specific mutations as a result of the abundant opportunities to reproduce.
These were not deemed significant enough to meet the definitions of new variants. They have, however, had slightly different properties.
For this reason they have been referred to as “subvariants”. BA.2 first appeared, and it was discovered to be slightly more infectious than the original Omicron, BA.1.
What exactly are recombinants?
There are now many Omicron subvariants, such as BA.4, BA.5, and BA.2.12.1. BA.4 was discovered in January and is essentially a cross between BA.1 and BA.3, with some new mutations that make it slightly more infectious than previous subvariants.
When viruses replicate inside host cells, they can collect pieces from multiple strains or variants at random if the host cell contains both strains or variants.
Because this is essentially a combination of both viruses, the process is known as recombination. When this occurs, the resulting “recombinant” virus can have characteristics of either or both viruses.
With inputs from the Conversation
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