Hundreds of thousands of Sydney residents have been told to stay home after a new outbreak of coronavirus ended a two-week run of no local cases.
Residents now face curbs on travel to the country's other states.
The new cluster has sparked national concern and cast uncertainty over many Australians' plans for a relatively normal Christmas.
Epidemiologist Michael Baker told Heather du Plessis-Allan it's a moving response, and Australia is waiting to see the extent of the outbreak.
"People are mobile, they travel across town a lot. I would be surprised if there are not more cases in Sydney that come up over the weekend."
Baker says the evidence in favour of elimination is more compelling now, from a health and economic perspective.