Australia is facing "three different pandemics", which will make it a challenge to come up with a solution to border controls.
That's the view of the country's deputy chief medical officer, Nick Coatsworth, as Prime Minister Scott Morrison and state and territory leaders grapple with the health and economic impacts of border restrictions.
Mr Morrison and other leaders will meet on Friday to discuss how to define a "hotspot", which will be crucial to how controls on travel are put in place or lifted.
Dr Coatsworth said it would be a challenge to find the right definition.
"We have clearly got three different pandemics going on in the country at the moment," he told reporters in Canberra.
"We have got Victoria, which is really pleasingly, after a really difficult time, coming down off its second wave.
"We have got the next two most populous states, NSW and Queensland, doing the best to avoid a second wave. Then we have four states with no community transmission at all."
He said once a definition could be found, it then became a question of what to use it for.
"It is obviously an issue of significant national interest and the premiers and PM will be discussing it next Friday," he said.
Mr Morrison says the pandemic should not be used to "retreat into provincialism".
He said the hotspot definition would be essential for moving away from border restrictions, with a greater focus on other containment strategies.
"If you impose a border, you can't help but cause problems. That's why we got rid of them in the first place," the prime minister said.
The prime minister praised Denmark, which has a traffic light system for travel restrictions based on the number of infections per 100,000 people.
Border closures have come under renewed scrutiny after the death of an unborn NSW twin whose mother was unable get approval to enter Queensland in time for emergency surgery.
Victoria recorded 18 deaths and 94 new cases on Saturday, while there were 14 fresh infections in NSW and four in Queensland.
The national death toll is now 601.
Australia also reached another milestone, having now clocked up over six million coronavirus tests since the beginning of the pandemic.
Chief Nursing Officer Alison McMillan said Victorians should be heartened by the number of new cases announced on Saturday, the first time the number has dipped below 100 since July.
The number of people requiring hospitalisation is also drastically falling.
"We have 510 people in hospital and that number over the last seven days has continued to decline significantly and that is an extremely positive to see," she told reporters in Canberra on Saturday.
But, Ms McMillan urged Australians not to become complacent as community transmission in NSW and Queensland continues to grow.