A new sister subtype of the Covid Omicron variant, which may be more transmissible and harder to track, has begun rearing its head overseas in recent days.
The subtype is being referred to as BA. 2, while the original Omicron, is known by scientists as BA. 1.
While cases of the BA. 2 type of Omicron remain low across various European countries, it could be just a matter of time before it arrives in Australia.
Scientists are still however working to determine whether the subtype, which had infected 53 people in the UK up to January 10, is more severe than the original BA. 1 type.
While the Health Security Agency has designated BA. 2 as a variant under investigation, its UK incident director Dr Meera Chand said such subtypes were to be expected.
"It is the nature of viruses to evolve and mutate, so it's to be expected that we will continue to see new variants emerge," she said, according to Metro.
There had been early indications the BA. 2 type may be more transmissible than BA. 1, however in Denmark, where it accounts for about half of Omicron cases, no stark differences in hospitalisations had yet been noted.
Denmark's Statens Serum Institute this week said it was likely vaccines had an effect against severe BA. 2 infections, which had several differences to BA.1.
One difference was that BA. 2 had shown positive for the S-gene, while BA. 1 did not.
The lack of S-gene in BA. 1 was a key component in tracking Omicron's early spread, as it was a feature that distinguished it from Delta.
The same feature however may be what makes BA. 2 infections harder to track.
Scientists are still confident it will be picked up in certain tests though.
Virologist from the Imperial College of London, Tom Peacock, said while early trends suggested BA. 2 was more transmissible, more research was required.
"BA. 2 appears to be the major Omicron lineage in (part of) India and the Philippines and there is evidence it is growing compared to BA. 1 in Denmark, the UK and Germany," one recent tweet read.
"Consistent growth across multiple countries is evidence BA. 2 may be some degree more transmissible than BA.1. This is the main reason BA. 2 is currently in the news.
"Unfortunately, this is really where the evidence mostly ends – we do not currently have a strong handle on antigenicity, severity or a much evidence for how much more transmissibility BA. 2 might have over BA. 1 – however we can make some guesses/early observations."
He added how "very early observations" from India and Denmark suggested there was no dramatic difference in severity when compared to BA.1.
"This data should become more solid (one way or another) in the coming weeks," he said.
Peacock also predicted BA. 2 would not have a "substantial" impact on the Omicron wave, which he expected was past its peak already in many countries.