ACT Health Minister Rachel Stephen-Smith confirmed a second baby and a unit team member at Canberra Hospital's Centenary Hospital for Women and Children were among the 41 positive cases announced on Thursday.

It comes one day after a baby, who had been in the special care nursery for some time, tested positive on Wednesday.

The baby first began showing symptoms of coronavirus on Tuesday night.

Two carers, who had visited the nursery, were also confirmed to have tested positive to COVID-19, bringing the cluster's total to five.

The outbreak has forced 28 health workers into quarantine as a result of the exposure.

Ms Stephen-Smith said neither baby was in critical condition but one had been moved to a COVID ward.

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She flagged there could be additional cases from the cluster to come but was confident the infectious diseases team would be able to prevent a large outbreak.

"I also have a lot of confidence in the infectious diseases team within Canberra Health Services and the infection prevention and control measures that are in place," she said.

"We have seen from previous exposures, and potential exposures across our hospitals, a very low rate of onward transmission within the hospital setting.

"I hope that that continues to be the case in this cluster as well."

Ms Stephen-Smith said the growing cluster shouldn't dissuade anyone from heading to the major hospital should they require medical attention.

"I would like to again reassure Canberrans that this situation is being expertly handled, and that people can feel safe to attend hospital should they require hospital care," she said.

"Our health services have strong measures in place to protect everyone, including the use of personal protective equipment, visitor restrictions and screening for everyone who is entering a health facility."

Ms Stephen-Smith earlier flagged "one, if not two" additional cases would be announced on Thursday.

Investigations into the source of the initial positive case are still under way.

Canberra Health Services interim chief executive Dave Peffer said on Wednesday the special care nursery was one of the few places in the hospital where special visitation arrangements were in place.

"We know that parents need to come in each day to potentially feed or provide that close care to the babies," he said.

"And so at this stage, we don't have a known source of transmission."

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