The South Australian and New South Wales governments are deliberating whether to open borders to Victorians in regions where there are no coronavirus cases.

South Australian Premier Steven Marshall said it was too early to make the call - his government relies on information from Victoria's health department - but he had not ruled it out. And Victorian Premier Daniel Andrews has supported the idea.

Deakin University epidemiology lead Catherine Bennett said COVID-19 risks were particularly small between regional Victoria and South Australia but she would prefer Victorians all have the option to move together.

Professor Bennett felt Melbourne would move to step three far sooner than the proposed October 19 date.

In looking at active COVID-19 cases within metropolitan Melbourne, Professor Bennett said three-quarters of cases were in aged care and, excepting this, Melbourne's 14-day average case rate is 3.2 - less than the required five average to move to step three.

Regional Victoria's average is 0.2 and there and only three active coronavirus cases that remain in regional Victoria in Colac-Otway, Mitchell and East Gippsland shires. The last mystery case in regional Victoria was on September 1.

Professor Bennett said Melbourne was also serving up one mystery every couple of days. Mystery cases need to be zero.

"If they do open the borders, it might help the premier remove the 'ring of steel' around Melbourne," Professor Bennett said.

"There are about 100,000 people moving between metropolitan Melbourne and regional Victoria daily to little effect...It is safe. The focus should be on how to get on top of outbreaks. If we all had the same level of restrictions on movement this would be much easier."

Professor Bennett said opening borders to regional Victorians was also likely to create a mess in logistics for how to prove on border checks whether you were from Melbourne or regional Victoria.

Premier Andrews said he had not yet had a discussion with his NSW or South Australian counterparts on opening to regional Victorians but he was open to it, especially for border communities.

"It makes perfect sense if you can travel from Mildura to Orbost based on the fact both communities have very low virus, it makes sense travel through that pretty arbitrary border," Premier Andrews said.

"A lot of people in those eight to nine border towns are Victorians, but they travel into South Australia to get their fuel, groceries and the like."

Premier Andrews urged Victorians to be patient when it came to travel. He said while no-one appreciated the restrictions, the vast majority of Victorians were doing the right thing.

But it had to be safe and steady steps to re-opening.

Regional Victoria moved to step three a fortnight ago.

Ballarat has not had an active COVID-19 case for more than three weeks. In the Pyrenees, Golden Plains, Moorabool and Hepburn shires there are zero active cases. Moorabool returned to zero cases on Tuesday this week.

"We are certainly looking at further steps to be taken in regional Victoria, but they have to be safe and steady steps," Premier Andrews said.

"I would say whilst there are low case numbers in regional Victoria which is pleasing pleasing, and all reports about Victorian businesses being serious about COVID safety, it's only a couple of weeks.

"We have to await the two to three week cycle (for the virus infection). These arrangements are not longstanding.

"...We can see these numbers steadily coming down, we can see strategy working, and we know you can't shortcut this, you can't cheat your way to a COVID normal."

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