The Department of Health reported just one new case on Thursday, a returned international traveller in hotel quarantine.

The result comes from 30,261 tests received in the 24 hours to midnight on Wednesday.

"That's basically 70,000 tests over the last couple of days," an upbeat Premier Daniel Andrews told reporters on Thursday.

"Every Victorian should be proud of that. I'm proud of them and I'm very, very grateful to them."

It comes as schools, offices, restaurants and shops emerge from the state's snap lockdown and with people allowed to leave home for any reason.

Mr Andrews has confirmed a support package for impacted businesses will be unveiled early next week.

Jobs, Innovation and Trade Minister Martin Pakula says the assistance will extend to hospitality venues, tourism operators and florists.

"We're working on making sure that it's appropriately targeted," he said.

"A five-day lockdown is quite different to a much more extended lockdown."

Restrictions haven't completely wound back to pre-lockdown levels, however, with a new suite of changes to remain in place until at least February 26.

Masks are now mandatory indoors and out when physical distancing isn't possible, while home gatherings will be limited to five visitors, down from 15.

Public outdoor gatherings are also capped at 20 people, down from 30.

Gyms, community facilities and entertainment venues can reopen, while religious gatherings and ceremonies will be able to resume, subject to density limits.

Thousands of fans are able to return for the final days of the Australian Open tennis tournament, with crowds at Melbourne Park to be capped at 50 per cent capacity.

Victoria's five-day lockdown was announced last week amid fears the highly-infectious UK strain of COVID-19 had spread from the Holiday Inn quarantine hotel at Melbourne Airport into the community.

The outbreak now stands at 19 cases, 15 of which have been shown to have the B1117 variant through genomic sequencing.

About 3400 close contacts remain in isolation with Health Minister Martin Foley warning more potential positive cases could emerge from that group.

"There is still some way to go but so far so good," he told reporters.

Testing chief Jeroen Weimar said officials had door-knocked more than a thousand close contacts in recent days to check they were isolating.

Two or three were found to not be in the right place, he said. None have been fined as they provided "legitimate explanations".

Mr Weimar also confirmed a resident at Reservoir's Twin Parks Aged Care Centre has returned an "indeterminate" fourth test result for COVID-19.

The man, who had the virus last year, returned a weak positive following two negative tests and is believed to be a case of viral shedding.

Meanwhile, the government's plan to extend its state of emergency powers is looking in doubt after negotiations with key upper house crossbenchers failed.

Reason Party leader MP Fiona Patten said on Wednesday she would vote against the bill and urged the government to bring forward legislation specific to the pandemic.

Australian Associated Press