BA.2 Omicron subvariant of COVID-19 has arrived in Australia. Here's what you need to know

Health officials around the world are watching to see if the new Omicron subvariant - known as BA.2 Omicron - will prove more severe and more vaccine-resistant to its original.

The BA.2 Omicron was first discovered in southern Africa, which was also where the original Omicron variant was identified last year.

Since its identification around the beginning of November 2021, the BA.2 has spread across the world, becoming particularly strong in Europe.

At the time of publication, up to 82 per cent of new cases in Denmark have been identified as the BA.2 subvariant.

In December, a patient in Queensland was found to be carrying the subvariant.

Associate Professor Stuart Turville from the Immunovirology and Pathogenesis Program at the Kirby Institute from the University of New South Wales (UNSW) has said that while it's a concern, it still represents a small number of cases in Australia.

"To date, BA.2 represents 2.8 per cent of Omicron sequences. Only 0.3 per cent of Omicron cases represented in Australia are the BA.2 variant, and it has been detected in Tasmania, ACT, Queensland, WA and Victoria," said Associate Professor Turville said.

But the fear is that the subvariant is more infectious and more vaccine-resistant to its parent.

If a household contact tests positive you have a 39 per cent probability of being infected within seven days. Compared to 29 per cent chance of infection with the BA.1 Omicron.

There has not been an increased risk of hospitalisation between the variants. Which has given authorities cause for optimism.

"BA.2 looks to be outcompeting the original Omicron particularly in Denmark," said Associate Professor James Wood, infectious disease epidemiologist, and modeller from the School of Population Health at UNSW.

In the United Kingdom, PCR test results show a drop in the BA.1 Omicron cases while BA.2 is rising, with early indications that the same will occur in Australia.

"There is very little data about virulence or the degree to which it escapes previous immune responses to date but I'd expect that to start emerging in the next couple of weeks," Associate Professor Wood said.

"My overall take at the moment is that this is a bit more transmissible than Omicron classic and will replace it over the next couple of months in Australia but that I don't expect it to immediately cause a new epidemic wave or to lead to a major change in disease severity."

Professor Seshadri Vasan of the CSIRO though has said it is too early to know what the effects of the subvariant will be on the Australian population. Rather, Professor Vasan says it's "no cause for concern" at this time.

"So far, evidence from our colleagues in Denmark shows that while it could spread faster, there is no evidence of increased severity," Professor Vasan said.

"It's absolutely normal for the SARS-CoV-2 virus to continue to evolve, and each variant of concern or VOC is just a punctuation in the evolutionary story of this virus.

"Keep calm and continue existing measures such as getting ourselves vaccinated, including the booster dose, and following social distancing, masks, and local guidelines."