Canberrans have been warned mandatory quarantine for people returning from South Australia could be imposed at any time as the state's coronavirus cluster grows.
Seven passengers flying in from Adelaide since Monday have been tested for coronavirus and asked to isolate after showing symptoms.
Health Minister Rachel Stephen-Smith said any decision on whether or not to impose mandatory quarantine restrictions rested on how confident ACT health officials were with the state's response to the outbreak.
Anyone returning from the state would not be allowed to enter ACT healthcare facilities for 14 days.
Travellers arriving at Canberra Airport from South Australia are undergoing health screening on arrival.
On Monday, five people were tested for coronavirus and told to self isolate after arriving in Canberra with symptoms. A further two were tested on Tuesday afternoon,
Ms Stephen-Smith said it was unlikely any of them would return a positive COVID-19 test.
She said all Canberrans should cancel non-essential travel to the state.
"We know, as we saw in Victoria, how quickly these situations can potentially escalate," Ms Stephen-Smith said.
"While we are really confident that South Australia is responding appropriately in terms of contact tracing and people going into quarantine, we know there is a possibility for these things to escalate very quickly."
The ACT has not imposed border or quarantine restrictions with South Australia, but Ms Stephen-Smith said that could change depending on how the outbreak unfolded.
Any hard-border closure would occur on the back of a decision by the NSW government.
She said there was not a particular trigger that would force the government to impose quarantine rules.
"You can't put a hard and fast number on it, it's actually about how confident we are of the other jurisdiction having a handle on cases and clusters and the risk of that escalating into another wave and being contained," Ms Stephen-Smith said.
"We need to remember we have consistently seen new cases and clusters in NSW and NSW has been able to respond to those very appropriately to date.
"We've been able to manage that response appropriately without putting restrictions on people who are travelling from Sydney, other than those who are visiting health facilities."
Anyone who has been in South Australia in the past 14 days will not be allowed to visit or work at ACT hospitals.
As of Tuesday afternoon, the so-called Parafield cluster in Adelaide had grown to 20.
All are in hotel quarantine, except for two from the new outbreak who have been admitted to the Royal Adelaide Hospital as a precaution because of their age.
Three staff, including two security guards, from one of Adelaide's quarantine hotels are among those who tested positive.
Staff at all quarantine hotels will now be tested weekly.
The growing cluster has prompted the SA government to reimpose a range of coronavirus restrictions.
From Tuesday, all gyms, recreation centres and play cafes are closed for two weeks with community sports fixtures and training cancelled.
Funerals and family gatherings are now capped at 50 people, and all church gatherings at 100 people.
Pubs, clubs and restaurants are limited to 100 people along with all other public gatherings.
All venues must abide by a rule of one person to every four square metres.
Masks are mandatory for workers in personal care businesses and for workers in aged care if physical distancing is not possible.
Aged care workers will be limited working at just one site but schools will remain open.
The government has also asked all people to work from home if they can and to reconsider unnecessary travel of any kind.