Chief Health Officer Brett Sutton said modelling suggested Monday's number of new cases could mark the peak of the crisis, but warned the days ahead would be most telling.

"Modelling, with our effective reproduction number that I have seen most recently, suggests that today should be the peak," he told reporters.

"I'm not going to sit back and say today is the peak. We have to see what happens in coming days."

Premier Daniel Andrews said people who are going to work sick - including those who work at aged care facilities - are the "biggest driver" of the state's second wave.

He warned the state's six-week lockdown, which started on July 8, would not end until people stop going to work with symptoms.

Mr Andrews even flagged the possibility some industries could be shut down.

"If we were to continue to see outbreaks, if we were to continue to see people quite obviously attending work when they shouldn't be, then every option becomes on the table," he said.

The latest deaths include a woman in her 90s, a man and a woman in their 80s, a man and a woman in their 70s and a man in his 50s.

Five of the deaths linked to aged care outbreaks.

Victoria has reported 58 deaths in the past six weeks, taking the state's toll to 77 and the national figure to 161.

In that period, active cases of the virus in the state have leapt from 51 to 4542.

"These are very challenging numbers. We're at a very challenging stage with this wave," Prof Sutton said, noting outbreaks in aged care were particularly distributing.

There are now 84 cases linked to St Basil's Home for the Aged in Fawkner, 82 at Estia Health in Ardeer, 77 at Epping Gardens Aged Care, and 62 at Menarock Aged Care in Essendon.

Glendale Aged Care in Werribee has 53 cases linked to it, and 57 are associated with Kirkbrae Presbyterian Homes in Kilsyth.

Opposition leader Michael O'Brien said families of people in nursing homes were understandably distressed at the surge in cases, and residents should be allowed to leave the facilities.

"We need to make sure that these people are treated with respect, with dignity, and are looked after in a health status," he said.

"So if that means getting some of them into hospitals, getting some of them into family homes while this pandemic is going, then I think the government should be supporting that."

An outbreak has also emerged in the neonatal intensive care unit at the Royal Children's Hospital, with two parents, a patient and a healthcare worker infected.

All babies, staff and parents who have visited the ward since July 12 will be tested.

Meanwhile, case numbers in hotspot areas, including the residential towers in Flemington and North Melbourne, have started to plateau, showing that testing and isolating could be effective, Prof Sutton said.

Prime Minister Scott Morrison said it would take the efforts of the entire state to drive down Victoria's case numbers.

"We just ask for the continued cooperation and goodwill of the people of Melbourne and Victoria ... to ensure that we can get on top of this," he told reporters.

Australian Associated Press