Workers at Canberra's only quarantine hotel have been told to avoid large crowds as they deal with four coronavirus cases.
The ACT's coronavirus case tally increased to four on Sunday with a man and a woman in their 40s testing positive.
The woman is the mother of a teenager who was confirmed as an active coronavirus case last week.
The ACT's rollout of the AstraZeneca vaccine is expected to start at the Garran Surge Centre on Wednesday.
ACT Health Minister Rachel Stephen-Smith said authorities might never know where the cases originated from, but the "working hypothesis" was they were infected during transit.
Before Australian travellers are allowed to board repatriation flights, they have to test negative to COVID-19.
Ms Stephen-Smith said it wouldn't be surprising if more COVID-19 cases came up in Canberra's hotel quarantine.
"If we don't, that'll be great, but if we do, that wouldn't be that surprising because there are more close contacts within the hotel quarantine system," she said.
She stressed workers at Pacific Suites on Northbourne Avenue were well-placed to manage the coronavirus cases with strict infection prevention and control measures.
The minister told ABC Radio Canberra on Monday morning hotel workers had been advised to avoid large crowds and events.
"There's also an encouragement for the staff, including when these positive cases came back, to say to them, 'Look, you're working in hotel quarantine - it would be better if you don't go out to crowded places'," she said.
"We know it's been a busy long weekend with the balloon festival, please don't go and hang out in a crowd of other people if you're working in hotel quarantine."
Ms Stephen-Smith said she understood that was a "tough ask" for hotel quarantine workers, but they understood they were working to safeguard Canberrans.
"They also understand that the risk to them is very low because of all the procedures that we've put in place around infection prevention and control and personal protective equipment," the minister said.
She said the quarantine hotel had designated "red zones", including corridors where guests might open their doors, where workers weren't allowed unless they had on all of the appropriate personal protection equipment.
Ms Stephen-Smith said workers were subjected to a saliva test every time they had a shift and a nasal swab every seven days.
They also received a text every day to check they still didn't have symptoms.
Of the ACT's active coronavirus cases, the first two that tested positive have been identified as having the South African variant of the virus, which is believed to be more infectious than other strains.
ACT health authorities are working based on the assumption the other two cases also have the South African variant, but the two new cases will have whole genome sequencing done in the next few days.
Canberra's hotel quarantine processes have been set up with variants in mind.
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