Victoria closes border to South Australia after outbreak

Mr Andrews said there would be a testing push at Portland, and also Benalla in the state's north, where virus fragments were detected in wastewater.

"With community transmission clearly happening in South Australia and in light of the wastewater results along freight routes in Victoria, the government is following the public health advice and has made the difficult decisions to introduce temporary border controls with South Australia," he said.

Acting Chief Health Officer Allen Cheng said the fragments were found in wastewater samples on Tuesday that had been clear of the virus last week.

Professor Cheng said the viral fragments could either be from an active case, or a recovered case who may still be shedding the virus.

"It's always difficult to interpret," he said. "It is possible that a recovered case for Melbourne has visited these areas."

Anyone who had been in Benalla or Portland since Sunday with any symptoms should get tested immediately, he said.

Professor Cheng said the change in Victoria's approach to the border came after the "concerning" developments in South Australia and the detection of the fragments.

South Australia is now under a tight six-day lockdown with schools, workplaces and all non-essential retail closed. The state recorded no new cases on Thursday although more than a dozen suspected cases are under investigation.

South Australia's outbreak – seeded, like Victoria's second wave, at a quarantine hotel – grew by two cases to a total of 22 on Wednesday, with seven suspected cases awaiting test results and more than 4000 close contacts in quarantine or self-isolation.

Mr Andrews said Victoria Police had worked through the logistics of the lockdown since Wednesday which will include checkpoints from midnight on Thursday.

Victoria Police Assistant Commissioner Rick Nugent said the force would have 24 hour checkpoints set up at the border from midnight Thursday.

No defence force personnel will be used to man the border, he confirmed.

"We’re looking at around between two and three hundred police resources to cover all of the border from Mildura right the way down," he said.

"Those resources will be drawn from road policing command, general duties and also transit public safety command."

Eradication in Victoria looms

The move came as Victoria recorded 20 consecutive days without a new coronavirus case, as South Australian residents woke to their first day of a harsh six-day lockdown aimed at stemming a growing outbreak in Adelaide's northern suburbs.

If Victoria records another eight days of zero new cases, the virus will be presumed to have been eradicated in the community, according to Dr Bruce Thompson, the Dean of Health at Swinburne University.

"I think everyone is surprised by how good it is," he told radio station 3AW. "For us to eradicate it would be absolutely amazing."

In measures tougher than those imposed during Victoria's second coronavirus lockdown, South Australians are now restricted from leaving their homes and banned from all outdoor exercise until next Tuesday. Only one person per household is allowed to undertake essential activities such as shopping each day.

South Australian authorities said the unprecedented lockdown was designed as a "circuit-breaker" to halt the spread of the virus.

Dr Thompson said six days may not be long enough as COVID-19 could take as long as 14 days to incubate in a person's body.

"I think it's slightly on the short side to be perfectly honest," he said. "If you’re only aiming for one incubation period, you’re losing your margin for error."

Dr Thompson said while it was encouraging that South Australia was taking lessons from how Victoria's deadly second wave unfolded, he questioned the need for the entire state to be locked down as all cases had so far been isolated to metropolitan Adelaide.

"I would probably suggest they’re being extremely harsh by doing that," he said.

Quarantine hotel risks

Mr Andrews said his government was "well and truly alive" to the risks of the protocols around hotels quarantine workers, ahead of the restart of Melbourne’s hotel quarantine program for international arrivals.

It has been revealed that a COVID-positive security guard who worked in one of South Australia’s ‘medi-hotels’ also worked part time at a pizza bar which has now been named a high-risk hot spot because the employee worked for 10 days while infectious.

"Everybody who works in [the Victorian] program will either work for this program, will either work for the Victorian government or be exclusively contracted for this purpose and this purpose only," he said.

"We will advance contact trace every single person who works in this program to work out who they live with, what those people do for a living.

"For instance we don’t want a situation where someone is sharing a house with an aged care worker - we think that would be an unreasonable risk."

Federal Health Minister Greg Hunt said the federal government supported the severe lockdown in South Australia, but disputed the assertion that support was in contrast to the rhetoric towards the Victorian government during that state's second-wave lockdown.

"With great respect, that’s an incorrect representation," he said to ABC Radio Adelaide host David Bevan.

Mr Hunt took aim at the length of the second Victorian lockdown, and the disputed point that Victoria refused Australian Defence Force assistance.

"We wanted Victoria to go hard and go early and we did the absolute best to get the Australian Defence Force in, not just at the start in March but again in June and July," he said.

"When the Victorian response had gone on for 100 days of lockdown, not six days, we were deeply concerned about mental health."

Despite South Australia's extraordinary restrictions, residents are still able to fly interstate to Victoria.

Two flights from Adelaide and Mt Gambier are due to arrive in Melbourne on Thursday, with all passengers to be health screened.

Truck drivers entering Victoria from South Australia on the Western Highway are already being tested at Nhill, 60 kilometres east of the border.

Drivers will be able to continue their journey after their fast-tracked results are sent to them, according to Victoria's health department.

Presuming Victoria's run of zero cases continues, Mr Andrews will announce a further relaxation of coronavirus restrictions on Sunday.

Mr Andrews said he did not believe the detection of viral fragments would affect the planned announcement of further eased restrictions on Sunday.

"I don’t think so, I think we are well placed to make changes that I had foreshadowed a couple of weeks ago on Sunday. That’s very important for jobs, so we think it’s proportion to the public health challenge that we face," he said.