From 6pm, non-ACT residents will need to give a valid reason to enter the territory and get an exemption from ACT Health before they travel.

Returning residents also need to inform ACT Health of their travel intentions through an online declaration form (which will be available from 10pm Monday).

Anyone who has entered the ACT since March 15 after visiting greater Brisbane has been asked to go into home quarantine until at least 6pm on April 1, even if they test negative to the virus.

It is possible the quarantine period could be extended beyond April 1 if there is evidence of wider community transmission in Brisbane.

The new direction includes: the City of Brisbane, City of Ipswich, Logan City, Moreton Bay Region and Redlands City.

ACT Health Minister Rachel Stephen-Smith said people in home quarantine could wait until Tuesday to get tested because of very long wait-times at testing centres on Monday.

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Ms Stephen-Smith said there were two close contacts and 11 casual contacts identified in the territory, as of lunchtime Monday. Both close contacts were awaiting test results.

"If we get any other positive cases in the ACT, we will then inform Canberrans of any places they have been that may present a transmission risk," she said.

The minister said Queensland Health could be contacting more Canberrans in its contact-tracing process in coming days.

"If you're in the ACT considering travelling to greater Brisbane, we ask that you do not travel at this time," she said.

"We know that this is going to be disruptive for people who have travel plans in place, but it is absolutely essential that we take a precautionary approach."

"If we start to see a cluster, we then run the risk of having to tighten our own restrictions and that has a massive economic impact across our community.

"If you do need to travel to greater Brisbane in an extraordinary circumstance, you will need an approved exemption from ACT health."

People who were in greater Brisbane from March 11 to 14 are also asked to get a COVID-19 test and isolate until they receive a negative result. They do not need to complete the mandatory quarantine until April 1.

Ms Stephen-Smith was "working through" the logistics of how exemptions would be checked upon residents' arrival.

"I haven't got advice at this point in time as to whether ... ACT Health will be meeting flights at the airport," she said.

"We will rely, as we have the whole way through, on Canberrans doing the right thing."

With vaccinations well underway in the ACT, Ms Stephen-Smith said only 15 per cent of the most vulnerable people identified in phase 1b of the roll out had been vaccinated.

"If we did start to see a cluster, or potential community transmission in the ACT, that would have an impact of the restrictions in place," she said.

"The reason we take these strong measures when we start to see a cluster in another jurisdiction ... is so that we can ensure that for the rest of us, life is as normal as possible."

"Everyone will be rolling their eyes and saying, 'Oh, no not again'. But it is really, really important that we are not complacent.

"It's really, really important that everybody understand if you have the mildest of symptoms, please go and get tested."

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