Anyone in Canberra who has visited Brisbane in the past week has been ordered into 14 days' quarantine, after the Queensland capital was declared a coronavirus hotspot amid fears of a possible outbreak linked to the highly contagious UK strain.
ACT chief health officer Kerryn Coleman is urging Canberrans not to travel to Brisbane, and asked those already there to stay put, as the city enters a three-day lockdown at 6pm on Friday.
The snap lockdown of the greater Brisbane area was ordered after a cleaner at a quarantine hotel was diagnosed with the UK variant of COVID-19, which evidence shows is 70 per cent more contagious than other strains.
In rules announced by Dr Coleman on Friday, anyone in the ACT who has been in the Brisbane, Moreton Bay, Ipswich, Redlands and Logan local government areas on or since January 2 must complete an online declaration form and immediately enter a fortnight's quarantine.
Dr Coleman said the rules would be reviewed and people could be freed from isolation in just three days' time - depending on how the situation in Brisbane evolved.
"If Queensland is able to do a really good job in contact tracing and there is a lot of testing in the region, and it looks like transmission is very limited, then it is highly likely that a lot of people would not have to continue and complete the quarantine period," she said.
"I don't want to give people false hope, but I do want to flag that there are bits of information and decision points that will come in then."
Other states and territories moved quickly on Friday to place restrictions on greater Brisbane, following a request from Queensland Premier Annastacia Palaszczuk.
The three-day lockdown will see a stay-at-home order in place for people living in Brisbane, Ipswich, Logan, Moreton Bay and the Redlands council area, and masks made mandatory.
People living in those areas must not leave their house except for receiving or providing essential medical care, exercise within their neighbourhood, essential work or study that cannot be done remotely, and essential shopping for food and necessary supplies.
"We are going to go early and go hard," Ms Palaszczuk said on Friday morning.
"Think of it as a long weekend at home."
A number of cases of the UK strain have been detected in hotel quarantine in Australia, but the case of the cleaner is the first time it has slipped out into the community.
Health chiefs and political leaders have unanimously backed the Brisbane lockdown, which is intended to give local authorities an opportunity to assess the extent of the virus' spread.
"This is the first time in Australia we have seen transmission of an alternate genetic strain virus that we know is more transmissible," Dr Coleman said.
"We are all watching what is going to happen in Queensland very, very closely, and there will be important lessons to learn.
"At the moment we need to expect that we may need to do more and go harder [in response] with this particular strain of virus."
Meanwhile in NSW, fragments of the virus has been detected at a sewerage treatment centre in Ulladulla.
The treatment centre takes takes sewage from Narrawallee, Milton, Mollymook Beach, Ulladulla, Kings Point, Burrill Lake, Dolphin Point and Lake Tabourie.
NSW Health have advised that anyone who has visited those areas should monitor symptoms and get tested and self isolate if even the mildest symptoms arise.
Chief Minister Andrew Barr said there had been no virus fragments detected in Canberra's sewerage this year.