Most states and territories in Australia have detected a "very low number" of cases of the new "stealth" sub-variant dubbed "son of Omicron", the Federal Department of Health has confirmed.
This includes three cases in NSW, state authorities have told news.com.au.
An ACT health spokesperson said it had also seen a "small number of cases" of sub-variant BA.2 but the predominant type circulating in the community was still Omicron BA.1.
The BA.2 sub-variant has raised concerns over its contagiousness and has been detected in more than 40 countries, though it is most prevalent in Europe. It now accounts for almost half of all Covid cases in Denmark, for example, where it has overtaken the original Omicron variant.
Melbourne University clinical epidemiologist Professor Nancy Baxter told Today on Thursday that BA.2 might be more contagious than Omicron.
"So if it gets here, it may extend our waves, so our wave may take longer to get out of. But we don't know enough yet," she said.
On Friday, a Department of Health spokeswoman confirmed the sub-variant had been detected in Australia.
"Most states and territories in Australia have detected a very low number of the Omicron sub-variant BA.2 in respiratory samples submitted for testing," she told news.com.au in a statement.
"The early detection of BA.2 in Australia is a testament to the success of Australia's genomic sequencing strategy
"As with all variants, this will continue to be closely monitored."
A New South Wales spokeswoman told news.com.au there had been "three recent cases of Covid-19 with the BA.2 Omicron variant identified in NSW".
"NSW Health continues to closely monitor the evolving situation with Covid-19," she said in a statement.
BA.2 has been called "Omicron's sister", "Omicron's brother" and "Omicron's son".
"They call it the 'son of Omicron', but it's more of a cousin – it's a variant related to Omicron. It is spreading. We are particularly seeing it in Denmark. We don't know if it's going to be a problem yet," Baxter said.
BA.2 has yet to be designated a variant of concern by the World Health Organisation but scientists are interested in understanding whether it is different to the original Omicron strain when it comes to contagiousness and severity.
Maps created by the Wellcome Sanger Institute show the spread of BA.2 in the UK. It was practically non-existent in the UK at the start of January. A fortnight later, hotspots had appeared across much of the country.
The institute estimates there were 186 cases of the sub-variant by January 1, about 1700 in the following week and 4400 in the most recent week of data, ending on January 15.
Scientists are keeping a close watch on the recently discovered sub-variant to determine how its emergence could affect future pandemic spread.
The UK Health Security Agency (UKHSA) indicated last week it had designated the BA.2 sub-lineage as a variant under investigation (VUI), however BA.1 remains dominant in Britain.
The authority underlined that "there is still uncertainty around the significance of the changes to the viral genome".
"What surprised us is the rapidity with which this sub-variant, which has been circulating to a great extent in Asia, has taken hold in Denmark," French epidemiologist Antoine Flahault told AFP.
"[France] expected a spike in contaminations in mid-January: It didn't happen and perhaps that is due to this sub-variant, which seems very transmissible but not more virulent than BA.1," Flahault said.
Tom Peacock, a virologist at Imperial College, London, tweeted that the latest variant should not call into question the effectiveness of existing vaccines.
"Several countries are near, or even past the peak of BA.1 waves. I would be very surprised if BA.2 caused a second wave at this point. Even with slightly higher transmissibility this absolutely is not a Delta-Omicron change and instead is likely to be slower and more subtle," he forecast.
— with Sam Clench and AFP