The hospitalisation rate, however, has remained low, with just 0.7 per cent of the cases identified between December 1 and February 27 admitted to Canberra hospitals with the virus.

NSW Health Minister Brad Hazzard on Thursday told a budget estimates inquiry health authorities in that state expected COVID-19 case numbers would double in the coming weeks.

"Preliminary information indicates that ... in only another month to six weeks we could be looking at cases more than double than we are currently getting," Mr Hazzard said.

"It is concerning us greatly, that we are seeing an increase in daily cases."

The rise in NSW has been attributed to the BA.2 Omicron sub-lineage, which is understood to be more contagious than the earlier sub-lineage of the variant.

A spokeswoman for ACT Health told The Canberra Times in a statement on Thursday evening that a third of sequenced COVID-19 samples in Canberra over the last week had the BA.2 sub-lineage.

"As this is not a random sample of cases, we are unable to say if this is representative of what is occurring in the community," the spokeswoman said.

Less than 10 per cent of cases identified in the ACT are presently being sequenced to determine the virus strain. Hospitalised cases, high-risk setting outbreaks and returned overseas travellers are prioritised for sequencing.

The spokeswoman said the ACT had seen a slow increase in daily cases, which had come after community movement increased and further public health measures were wound back.

"This is likely due to a combination of factors including an increase in the case rate in the 5-11 year age cohort possibly leading to an in increase in testing in the 25-64 year age group from household and close contacts," the spokeswoman said.

The spokeswoman did not respond to a direct questions from The Canberra Times about the projected rate of hospitalisations over the coming month and whether case numbers would double.

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The most recent epidemiological report from ACT Health, which covers the week ending February 27, said the end of the summer holidays had contributed to a "slight increase" in total case numbers.

"This increase has not impacted on hospitalisations, with no increase in hospitalisation rates among school age children or young adults observed during the same time period," the report said.

The ACT reported 821 new cases of COVID-19 on Thursday. There were 37 people in hospital; two people were in intensive care, where one person was ventilated.

The World Health Organisation last month said the proportion of sequenced COVID-19 cases designated as BA.2 was growing relative to BA.1 while the global circulation of all variants was reportedly declining.

"Initial data suggest that BA.2 appears inherently more transmissible than BA.1, which currently remains the most common Omicron sublineage reported," the World Health Organisation said in a statement on February 22.

"This difference in transmissibility appears to be much smaller than, for example, the difference between BA.1 and Delta."

Infection with BA.1 provides strong protection against reinfection with BA.2, however cases of reinfection have been documented, the World Health Organisation has said.

In South Africa, the United Kingdom and Denmark, where immunity from vaccination or natural infection is high "there was no reported difference in severity between BA.2 and BA.1".

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