Omicron Subtype BA.2: What to Know About the Speeding ‘Stealth’ Variant

Although Omicron seems to have already peaked in many countries including India, data from genome sequencing suggests Omicron's cousin, a new subvariant may be taking over the baton.

The subvariant, BA.2, has already put health authorities in India, Denmark and the UK on alert, and more countries are expected to follow suit.

It's too soon to let our guards down just yet, but at the same time, before we start panicking, let's look at what we know about the Omicron subvariant, BA.2.

Is it more transmissible than Omicron?

Can it circumvent vaccine protection more efficiently?

Can it cause more severe illness than previous variants?

Omicron BA.2 Variant: What We Know So Far

Here's a quick run through of what we know about the subvariant BA.2, and it's emergence.

• The Omicron variant (B.1.1.529) has three significant subvariants that have been identified–BA.1, BA.2, and BA.3, according to the World Health Organization (WHO).

• So far, the variant behind the majority of Omicron cases was BA.1, so much so that it was being synonymously identified as Omicron.

• The BA.2 sub variant is closely related to the original Omicron variant BA.1, but has major mutations.

According to Dr Trevor Bedford, a scientist at Fred Hutchinson Cancer Center, Seattle, US, the Omicron subvariants are about as divergent from each other in terms of amino acid changes, as earlier variants Alpha, Beta and Gama are from each other.

• It is unknown where the subvariant originated.

• According to Global Initiative on Sharing All Influenza Data (GISNAID), an open source platform for genome sequencing data from across the world, 40 countries have, so far, detected BA.2.

• The variant seems to be gaining steam in Denmark, India, and the UK.

• BA.2 was classified as a 'variant under investigation' by the UK Health Security Agency (UK HSA) on 22 January.

"53 sequences of the BA.2 sub-lineage of Omicron had been identified in the United Kingdom...UKHSA are continuing to monitor data on the BA.2 sub-lineage closely."

Statement released by the UK Health Security Agency (UKHSA)

What Is Happening: 'The Stealth Variant'

The Omicron variant (BA.1) was promptly identified because it has a missing gene that distinguishes it from other variants.

The BA.2 variant, though closely related to BA.1 does not have that missing target gene, which was used earlier to detect Omicron. This makes it easier for the variant to slip through genome sequencing.

This is also why it's been dubbed 'the stealth variant'.

However, the subvariant can still be detected by home testing kits at the same rate as other variants.

Genetic changes in the BA.2 variant can change its behaviour, but to what extent, we don't know yet.

Is it More Transmissible, or More Virulent?

Based on early data, experts think the subvariant is more transmissible than BA.1.

According to a statement released by the Statens Serum Institut, a government-run infectious disease research centre in Denmark, BA.2 now accounts for half of the Omicron cases in Denmark.

Moreover, the subvariant is gaining ground fast, going from making up 20 percent of Denmark's COVID-19 cases to 45 percent in a matter of 1 week.

Preliminary studies conducted in Australia and by the UK HSA indicate that so far, it does not seem to have any more vaccine-evasive properties than BA.1 or Delta.

That being said, it may be too soon to tell just how transmissible it is and what this may imply.

As far as virulence is concerned, early observation suggests it doesn't cause more severe disease than BA.1.

"Initial analysis shows no differences in hospitalisations for BA.2 compared to BA.1," according to a statement released by the Statens Serum Institut, a government-run infectious disease research centre in Denmark.

However, it's too soon to bank on this not changing in the near future.

What Is the Situation Like in India?

Sujeet Kumar Singh, Director, National Centre for Disease Control (NCDC), on 27 January spoke about the prevalence of subvariant BA.2 in India, and warned that it was fast gaining ground.

"Earlier, the BA.1 variant was dominant among the samples collected from the travellers. Now, in community settings, we have found that the BA.2 sub-variant is gradually increasing," he was quoted as saying by IANS.

It isn't clear yet how much of the sequenced Omicron variants are made up of BA.2 in India, and which parts of the country they are concentrated in.

(Written with inputs from IANS.)