Greater Brisbane has been declared a COVID-19 hotspot for the purpose of commonwealth support as Chief Medical Officer Paul Kelly warns travellers to stay up to date with border closures.
States and territories moved quickly to impose entry restrictions following Queensland's decision to lockdown the city from 5pm on Monday.
The lockdown will be in place until at least Thursday evening, but Professor Kelly says the outbreak is escalating.
"It may be one thing to go there, but coming back might also be difficult," he said on Tuesday.
"I can't predict what's going to happen in the next week or two."
Another eight coronavirus cases emerged on Tuesday, with two clusters triggering concern the Greater Brisbane lockdown may be expanded and extended.
Premier Annastacia Palaszczuk says six new cases are genomically linked to or close contacts of seven existing infections, while the other two are under investigation.
She says there are now two distinct clusters of the UK variant of COVID-19 in Greater Brisbane, which has been locked down to stem the spread.
"We want to get on top of this community transmission," Ms Palaszczuk told reporters.
"The steps that we took to go into this lockdown, as you can see by those numbers of community transmission today, were absolutely the right call."
There are now more than 60 potential virus exposure sites across Greater Brisbane, the Gold Coast and central Queensland.
About 2.5 million people in Greater Brisbane were ordered into a snap three-day lockdown on Monday afternoon.
Hundreds more people around the state who have visited Brisbane since March 20 are also under orders to stay at home and self-isolate.
The premier raised the prospect that the lockdown could be extended past 5pm on Thursday.
"We just have to take this day by day, " Ms Palaszczuk said.
"Do we expect to see more cases? Probably we will see more.
"The big question will be whether or not we see unlinked community transmission."
One known case lives on the Gold Coast and others have visited Toowoomba, Gladstone, Hervey Bay and Gin Gin while infectious.
Chief Health Officer Jeannette Young has also left open the door to expand the lockdown to other regions.
"The message here is that people should be on alert, no matter where they are in Queensland," Dr Young said.
Queensland has also mandated that healthcare workers must have received their first vaccine dose to be able to treat COVID-19 patients.
The state opposition supports the move but said it should have happened sooner, criticising the vaccine rollout as sluggish.
"It stands to reason that maybe if these staff had been vaccinated (or) not been treating COVID-positive cases, then we might not be in a lockdown," shadow health minister Ros Bates said.
More than 41,000 frontline workers have received their first jab already, but only about 7000 are fully vaccinated.
Cases in both clusters are either genomically linked to, or close contacts of, two Princess Alexandra Hospital staff who tested positive.
The first cluster is genomically linked to a PA Hospital doctor who tested positive on March 12.
The cases linked to the doctor include two men in northern Brisbane, the brother of one of the men, and two colleagues of the other.
The second cluster is linked to a PA Hospital nurse and her sister.
A close contact, and another five people who went to a hen's party with the pair in Byron Bay, tested positive in Brisbane and the Gold Coast overnight.
Dr Young said another two cases were believed to be linked to the first cluster, but genomic testing was underway.
Australian Associated Press