ACT residents and Canberra visitors that have spent time in Greater Brisbane over the past 18 days have been asked to enter a form of quarantine.

Returning travellers to the national capital, arriving since March 15, must immediately self-isolate until at least April 1.

But ACT Minister for Health Rachel Stephen-Smith has warned that further COVID-19 cases throughout metropolitan Brisbane, Logan, Moreton Bay, Ipswich and Redlands could result in the travellers being forced to extend quarantine for 14 days from Monday (March 29).

“We just don’t know how this is going to fold over the next few days,” Ms Stephen-Smith said.

A three-day lockdown has been ordered for Greater Brisbane after four local residents had tested positive for coronavirus and were found to be a risk of transmitting the virus further after spending several days infected in the community.

The latest ACT measures that mirrors the Brisbane lockdown requires travellers to Canberra to complete an online declaration form prior to travelling, testing and quarantine.

“It is absolutely essential that we take a precautionary approach at this point in time,” Ms Stephen-Smith said.

“We know what happens if we start to see community transition, if we start to see a cluster, we then run the risk of tightening our own restrictions.”

ACT Health has identified from the manifests of flights between the two cities that about 5000 messages and/or texts are sent to people who have visited Greater Brisbane.

Essential travellers this week between Brisbane and Canberra over the following three days must gain an ACT Health exemption before boarding planes.

Ms Stephen-Smith that “at this point in time” there was no suggestion that Easter holiday plans to Queensland should be cancelled.

ACT Health will consider meeting flights at Canberra Airport, but land border measures are not a serious consideration.

“We will rely on Canberrans doing the right thing,” Ms Stephen-Smith said.