XBB.1.16 was first detected in NSW in February this year, with infections slowly rising.
ABC Pacific reports the World Health Organization (WHO) assessed this strain as "low risk" on a global scale, compared with others currently in circulation.
However, the strain was designated a variant of interest by WHO earlier this month, as cases surged in India.
WHO did say it was a strain to watch, designating XBB.1.16 as a variant of interest on April 17.
What is the new variant?
Subvariant XBB.1.16 has come to be known colloquially as Arcturus and is related to the XBB.1.5 subvariant, which was detected in Australia in January.
Both are mutations of the Omicron variant of SARS-CoV-2, the virus that causes COVID-19.
Studies on the Australian population indicate that in comparison, it is essentially "more of the same", according to Stuart Turville, an associate professor at the Kirby Institute at the University of New South Wales.
Dr Turville studied the new strain recently in several different vaccinated cohorts' representative of the Australian population.
"And then we've asked the question, this variant versus the others, what does it look like?" he said.
He found XBB.1.16 was similar to other common subvariants in circulation, and avoided antibodies with "equal evasiveness".
While increasing concern for its effect in south-east Asia was warranted, Dr Turville said it's not necessarily the case here, pointing to Australia's past unique "immune journey" along the pandemic's trajectory.
How fast is it spreading? Is it more dangerous?
NSW surveillance report samples indicate about one quarter of all dominant variations of Omicron are XBB.1.16, Dr Turville said, as of the week ending on April 15.
However, the significant reduction in PCR tests has resulted in a lack of data on new variants.
Michael Toole, Associate Principal Research Fellow at the Burnet Institute, said there was no evidence this strain was more severe, but pointed to studies in Japan that found it spreads more easily.
"All the Omicron variants have spread more easily than the previous variants," Professor Toole said.
"Each time … it gets a little bit more infectious and evades our immunity."
Will the vaccines protect us?
About 70 per cent of Australians have received a booster shot on top of their mandatory two vaccine doses.
Professor Toole said this is not enough, and we should be aiming for 90-95 per cent of the population boosted.
He said people who haven't been boosted — or infected — since their mandatory doses, effectively "have no immunity" due to the time lapsed.
Is there a new wave on the way?
There is no indication of a sharp spike as winter approaches, but cases are gradually increasing week-on-week, with the fastest increase found in New South Wales
As of March 17, Australia reported more than 22,000 new COVID-19 cases. Last week this had increased to more than 29,000.
NSW also recorded a slight surge in cases, with 12,393 COVID-19 infections recorded in the week ending April 20, up from 9,643 a week prior.
Hospitalisations are also increasing. In March some 1345 people were hospitalised in the week recorded up to March 17, while last week that national figure had increased to 2008.
"That figure is more reliable than case numbers," he said.
"You can't fake someone being in hospital."
When should I get vaccinated?
If it's at least six months since your last COVID-19 vaccination or confirmed infection, NSW Health says your immunity may be waning.
It's suggested that all adults consider a booster at this time, but for some high-risk groups — like those over 65 — it's strongly recommended.