The third case was announced late yesterday and was a 90-year-old resident from the Maidstone Acare facility.

It has not yet been announced where the other two cases are located.

While Melbourne must stay under stay-at-home orders for at least seven more days, Acting Premier James Merlino said "circuit breaker" restrictions would ease for regional Victoria if it stayed virus-free.

Victoria had another record day of testing, with 57,519 in the 24 hours to midnight on Wednesday.

If regional areas come out of lockdown, it would mean the removal of the five reasons to leave home, retail businesses reopening, and hospitality venues operating as seated service only.

What will the rule changes mean for regional Victoria?

COVID-19 has been detected in wastewater at Bendigo and Axedale, and there are exposure sites at Anglesea, Axedale, Glenrowan, Kalkallo, Wallan and Rye.

But none of the 60 cases linked to the current outbreak up to Wednesday had come from regional Victoria, earning it a likely lockdown reprieve just before midnight on Thursday.

The so-called "ring of steel", used last year to enforce the regional divide, will be replaced by roving police patrols.

Instead, the onus will be on regional businesses checking the IDs of customers, while Service Victoria QR code check-ins will become mandatory statewide in retail settings such as supermarkets.

The Victorian government has used evidence of the Indian variant being quicker and more contagious to justify Melbourne remaining in lockdown until 11.59pm on June 10.

"If we let this thing run its course, it will explode," Mr Merlino said.

"We've got to run this to ground because if we don't, people will die."

Professor Sutton said about 10 per cent of current cases caught the virus through "fleeting exchanges" with infected people.

There has been plenty of debate about the state government's comments on the nature of this outbreak, with some health experts doubting the virus strain is unusually contagious.

IN OTHER NEWS

Prof Sutton has "great confidence" restrictions will be eased at the end of the week but travel will still not be allowed from Melbourne to regional areas over the Queen's Birthday long weekend.

There are now 370 exposure sites listed on the health department's website, with several suburban bus routes from May 25-28 added on Wednesday night.

Thursday's figures are expected to include a second resident at aged care facility Arcare Maidstone who was taken to hospital after testing positive.

Arcare chief executive Colin Singh said the 89-year-old man was a cousin of the first COVID-infected resident and lived in an adjacent room.

Federal Aged Care Services Minister Richard Colbeck told a Senate estimates hearing the man initially returned an inconclusive result and had been fully vaccinated.

It takes the Arcare Maidstone outbreak to four cases, including two residents and two workers.

Fellow residents and staff members remain in self-isolation, with more testing planned for Thursday.

Meanwhile, federal Treasurer Josh Frydenberg again said on Thursday morning that he will consider Victoria's request for worker support from Canberra as the lockdown continues.

He added a Commonwealth decision on Victoria's proposal for a purpose-built quarantine facility will also be made soon.

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