The more transmissible Omicron BA.2 sub-variant is becoming the most dominant COVID-19 strain in the ACT, making up more than half of all sequenced cases in the territory last week.
It has prompted health authorities to make a fresh plea to Canberrans to come forward for their booster shot, saying the third-dose rate was not as high as it should be.
A rise in cases associated with Canberra schools was being mostly driven by household transmission and not virus spread within classrooms, authorities confirmed on Friday.
There has been a spike in COVID cases in the territory this week with the daily tally above 1000 for the past three days, but health authorities said the spike was not unexpected.
Hospitalisations were also expected to remain steady, with current forecasts suggesting the number of patients in hospitals at any one time was likely to be about 36.
There were 37 COVID-19 patients in hospital in the 24 hours to 8pm on Thursday. Four patients were in intensive care and one was being ventilated.
There were 1123 new COVID-19 cases reported in the ACT on Friday, as the BA.2 Omicron sub-variant started to take hold in the territory.
The latest epidemiological report from ACT Health showed in the week from March 7 to March 13 that 56 per cent of cases that had undergone genomic sequencing had been identified as BA.2. This was up from one-third the previous week.
Only 10 per cent of cases in the territory were sequenced and it was not a random sample as overseas returnees and patients in hospitals were prioritised.
ACT Health's Dr Robyn Walker, the acting executive group manager of the COVID-19 response, said the rise in cases was not unexpected and daily case numbers were in the range forecast by health authorities.
"We've had a lowering of our public health social measures, we've had a relaxation on mask-wearing, we've had an opening of our international borders [and] the BA.2 variant of Omicron, which is a bit more transmissible," she said.
But Dr Walker said the ACT's booster shot rate of 71.2 per cent in the over-16 population was not where authorities would like it to be and urged people to come forward.
"There's a number of measures of why the cases might go up. I'd put a plea in for people to get their booster dose because we know that helps protect people and we're not quite as a high as we'd like to be in that situation," she said.
Education authorities were bracing for a growing number of cases in Canberra schools but Dr Walker said a rise in cases in the five- to 11-year-old age group was expected, particularly as they were just eligible for their second COVID vaccine dose.
But she said the rise was mostly due to household transmission.
"We are seeing some increase in probably the parents or the carers ... it's probably transmission in the household that is the greatest risk," Dr Walker said.
