No big steps out of lockdown to be announced next Sunday: Andrews

The number of 'mystery' cases with an unknown source over the past two weeks - measured between September 24 and October 7 - is down to 10. There has been one new mystery coronavirus case confirmed in Victoria since yesterday, state health department figures show.

For Melbourne to move to step three of the government's original road map out of lockdown on October 19, Victoria's 14-day average for new cases was hoped to be below five. Under the plan, there was also meant to be five or fewer mystery cases between October 3 and October 16 in order for restrictions to be eased on schedule.

Melbourne is now within that crucial fortnight meaning that the case numbers we see every day are directly determining whether the targets are met.

The additional mystery case today brings the total number of cases with an unknown infection source recorded in Victoria since October 3 to five.

In short, this means that from now on Victoria cannot record anymore mystery cases in order to stay on target.

With 55 new cases recorded over the past six days, it also means that over the next nine days there can be no more than 15 daily cases recorded in total for the 14-day rolling average target to be met.

Melbourne was scheduled to see many restrictions ease on October 19, including the five-kilometre rule and limits on retail, hairdressing and outdoor dining. This date was originally set for October 26, but was brought forward.

Five-kilometre radius rule up for review

Melbourne's five-kilometre radius rule is "up for evaluation" alongside all lockdown measures this week, according to Professor Brett Sutton.

The Chief Health Officer confirmed dumping or changing the rule was definitely not off the table, even though Mr Andrews has confirmed the state will not take the full step out of lockdown as intended.

The five-kilometre rule has become a point of contention in the epidemiology community of late, with public health experts divided on the merits of the rule in slowing the spread.

"Certainly we'll look at all of those individual elements and try to tease them apart, looking against the transmission that we've seen occurring over recent weeks," Professor Sutton said.

"The five-kilometre limit in particular limits the number of households that you can meet outside by virtue of that constraint. But, of course, every single decision, every single element that we're looking at has that public health benefit versus the potential psychological or social harms."

Mr Andrews said the government and public health team would spend this weekend and all of next week re-assessing all the lockdown measures to see which ones could still be lifted the following week.

"It is in no way warranted for people to be despondent or for people to lose any sense of hope. This strategy is working, but you have got to do it properly," he said.

Melbourne now has a 50 per cent chance or less of meeting the October 19 thresholds, according to new Doherty Institute modelling released on Friday.

Professor McVernon and Professor McCaw, who provide modelling to the state government, said the behaviour of individuals would be crucial to controlling the spread of the virus.

"It's clear Melbourne cannot stay in lockdown indefinitely," they said. "Lockdowns are an emergency brake on widespread community transmission."

Professor Sutton said the outbreaks in recent weeks in permitted industries "clarified" in his mind how hard the goal of zero community transmission was but maintained it was still a viable goal.

"I think it's challenging. There's no question it's challenging. I don't think it is impossible," he said.

He said recent outbreaks were driven by people waiting too long to get tested and isolate.

"Part of what drives numbers now is that a couple of weeks ago, we saw that people were too slow to test from the beginning of symptoms, and people were too slow to isolate from the beginning of symptoms," he said.

"So they're the things that are contributing now to the cases that we're seeing and we need to turn that around."

16,647 tests were processed on Friday, while 21 Victorians are being treated for COVID-19 in hospital.

Saturday's 14 new cases were largely driven by known outbreaks, according to Professor Sutton, with six linked up to known clusters and eight under investigation as of Saturday morning.

One of the new cases is linked to a Kilmore cafe, bringing the cluster in the regional town to five.

724 people in Kilmore have been tested so far, while a case found in Mildura earlier this week has been found to be a false positive.

Box Hill cluster grows amid family transmission

Significantly, the Box Hill Hospital outbreak has jumped by six people since Friday and now includes 10 people in total.

Five of the six new Box Hill cases are all in one family, Professor Sutton said.

"There are five cases from a family being added today, so the outbreak comprises three staff, one patient and now six household contacts."

Professor Sutton said all cases were isolated, and all close contacts of the staff members are also quarantined.

Staff working on a ward at Box Hill Hospital where a patient and a nurse could have been infectious with coronavirus have been told they are not allowed to use N95 masks they purchased themselves as a precaution against the disease.

Professor Sutton said the hospital was legally obligated to make sure that all the staff have appropriate PPE, but that it was "absolutely right" for the hospital to say any masks worn needed to be TGA approved and up to standard.

10 more towns to receive sewage testing

10 more regional Victorian towns have their wastewater tested for fragments of COVID-19 as of Monday, bringing the total number of testing sites across the state to 40.

Bacchus Marsh, Gisborne, Melton, Portland, Warrnambool, Hamilton, Cowes, Horsham, Bairnsdale and Kilmore will all be tested under the scheme announced by Health Minister Martin Foley.

"That is very important because as we have found on the Surf Coast areas in recent times, while we do find fragments from time to time through that wastewater program, that gives communities an early indication of getting out there and getting tested," he said.