Australia's two most populous states are staring down the barrel of fresh COVID-19 outbreaks after three new locally-acquired cases were discovered in Victoria, breaking its 61-day infection-free run.
Three people in the Melbourne suburbs of Mitcham, Hallam and Mentone were on Wednesday evening confirmed to have COVID-19.
The cases - believed by Victorian authorities to be connected to COVID-19 cases in NSW - have sent more than 40 people into self-isolation.
They are the first local Victorian virus cases reported since October 31.
NSW, meanwhile, has declared a new six-person COVID-19 cluster in the inner-west Sydney suburb of Croydon - which has no clear links to the mystery COVID-19 cluster on the city's northern beaches.
NSW recorded 18 local cases of COVID-19 in the 24 hours to 8pm on Tuesday - nine of which are connected to Sydney's northern beaches area, which remains under lockdown due to its 138-strong virus cluster.
Six cases, all from an extended family, were connected to Croydon, while the final three cases in Wollongong and northern Sydney are under investigation.
The new local cases have prompted the NSW government to limit indoor New Year's Eve gatherings across all of greater Sydney to five people. The Sydney foreshore has already been closed off to revellers.
Victoria has also muted its New Year's Eve celebrations, cancelling fireworks in the Melbourne CBD and advising residents to avoid the city.
Chief Medical Officer Paul Kelly on Wednesday said he supported NSW's actions and believed NSW Health would squash the outbreak.
But the Northern Territory on Wednesday elected to ban residents from Sydney suburbs including Croydon, Strathfield and Sutherland from entry.
"NSW Health right throughout this pandemic have been our poster people, if you like, in relation to their contact tracing," Dr Kelly told reporters.
"It's always amazing how quickly they get onto things and how quickly they work through what are sometimes very complex chains of transmission."
Dr Kelly also said a highly-infectious variant of COVID-19 spreading around the world could be safely blunted by Australia's hotel quarantine system.
The first case in Australia of a contagious South African COVID-19 variant is a woman who arrived in Queensland on December 22. She was transferred to the Sunshine Coast University Hospital on Tuesday.
The World Health Organisation is yet to determine whether the new variant - and a similarly-contagious strain that developed recently in the UK - could undermine vaccines being rolled out around the world.
The first Australians are set to be vaccinated by the end of March.
Australia has identified five cases of the British variant in arrivals from the UK, including two in NSW, two in Victoria and one in South Australia.
Dr Kelly said the Australian Health Protection Principal Committee would meet on Wednesday and discuss the prospect of pre-flight COVID-19 testing but said Qantas was already performing that function on their flights.
He also said it was unlikely Australia would permit COVID-vaccinated international arrivals in 2021 from skipping 14 days in quarantine.
It comes after the federal government on Wednesday said it was considering granting "alternate entry" to Australians returning from overseas if they can prove they have already been vaccinated for the virus.
"Those decision also have to be thought through carefully over the coming months as to how that will be handled," Dr Kelly said.
Labor, meanwhile, on Wednesday again called for the establishment of a national quarantine centre to expedite the return of Australians overseas.