Premier Daniel Andrews on Sunday announced the new measure, which will take effect from 11.59pm on Wednesday for residents of metropolitan Melbourne and Mitchell Shire.

The two areas remain in lockdown, with people only allowed to leave their homes – with a mask on – to exercise, buy groceries, care or care-giving and to go to work or school if they cannot do so from home.

Another 275 coronavirus cases have been recorded in Victoria and a woman in her 80s has died.

There are 147 Victorians in hospital, 31 of those are in intensive care, Premier Daniel Andrews said on Monday.

Victoria now has a total of 5942 cases since the pandemic began, 2913 of those active.

Professor Sharon Lewin, director of the Peter Doherty Institute for Infection and Immunity, said masks will help control the virus spread.

However it could take more than a week to know if it is working.

“Any time you introduce an intervention with attacking this coronavirus you don’t see the result for about seven to 10 days which makes things very tricky,” she told Nine’s Today program.

People will risk a fine if they leave the house without a mask or face covering, such as a scarf of bandana.

An inspection blitz of at-risk workplaces will also happen after it was revealed about 80 per cent of new cases since mid-May are linked to workplaces.

The crackdown will include distribution centres, call centres and meat processing centres and be undertaken by police and WorkSafe.

Victoria on Sunday recorded 363 new cases of the virus and two more deaths, taking the state’s toll to 38, with more infections cropping up in nursing homes.

Thirty-eight cases and now linked to Estia Health in Ardeer and 24 have been connected to Glendale Aged Care facility in Werribee.

Aged care workers are being urged to stop working across multiple sites in a bid to stop the virus spreading further and the federal government is providing more money to the sector to ensure staff can earn more working at just one centre.

As the state continues to battle the COVID spread, an inquiry into how the second wave started is due to kick off.

The inquiry into Victoria’s now-infamous hotel quarantine program starts on Monday, led by retired judge Jennifer Coate, assisted by Tony Neal QC.

With almost 3,000 active COVID-19 cases, many the result of workplace transmission or community spread, Victoria is in an increasingly precarious position, and the Government’s strategy is evolving at pace.

Victoria’s Chief Health Officer, Brett Sutton, has described the state’s fluctuating coronavirus cases as “a numbers rollercoaster” — and there’s likely to be more twists and turns ahead.

The state recorded 363 new cases of COVID-19 on Sunday, up from 217 on Saturday but down from the record high of 428 on Friday.

Professor Sutton warned there was “no absolutely clear sign that numbers are decreasing”.

The increasingly precarious situation means the state’s strategy is constantly evolving, the rules keep changing and life for many people just gets more and more difficult.

Mandatory masks could be here ‘for a very long time’

From Thursday, wearing a face covering will be mandatory when outdoors in metropolitan Melbourne and the Mitchell Shire.

The Government argues it’s a low-cost, high-reward tactic to help stop the virus’s spread.

And Victorians have been warned they will need to get used to it.

“We are going to be wearing masks in Victoria, and potentially in other parts of the country, for a very long time,” Premier Daniel Andrews said.

“It’s about changing habits, it’s about it becoming a simple part of your routine.”

There are a few exceptions to the rule.

You don’t have to wear a mask if it’s not practical, such as in some work settings, if you’re doing vigorous exercise, or if you have a medical reason.

Children under 12 are also exempt.

Any face covering, including a scarf, will suffice.

Police will initially exercise discretion when it comes to handing out penalties.

But those people caught without a mask, and without a good reason, risk a $200 fine.

Tighter restrictions are looming

While a move to stage four has not been announced, the Government has warned it will continue to tighten restrictions if cases do not decline.

Andrews said if the Government saw a “high degree of compliance”, including people wearing masks and only leaving their homes for permitted reasons, further restrictions would be less likely.

“That will mean it is less likely we have to move to things like only doing that daily exercise, for instance, in your own local postcode,” he said.

“Or things like saying … you can only go shopping within a certain radius or certain distance from your home.

“We don’t want to get to those steps.

“If we have to, we will.”

Workplace transmission is the Government’s new target

About 80 per cent of the state’s new cases since mid-May have been driven by workplace transmission, the Government believes.

“So workplaces are a big part of our challenge,” Andrews said. “That’s where a lot of our problem is.”

Aged care is a major concern. There are now 216 cases of coronavirus linked to 40 aged care facilities in the state.

Some of the biggest clusters include:

• 169 cases linked to Al-Taqwa College
• 53 linked to meat-packing facility Somerville Retail Services in Tottenham
• 35 linked to meatworks JBS in Brooklyn
• 10 cases linked to St Basil’s Home for the Aged in Fawkner
• 38 cases linked to Estia Health in Ardeer
• 24 cases linked to Glendale Aged Care in Werribee
• 12 cases linked to Embracia Aged Care Moonee Valley in Avondale Heights

To ensure people are abiding by physical distancing rules at work, officers from Victoria Police, WorkSafe and the Department of Health and Human Services (DHHS) will begin inspecting high-risk workplaces such as call centres, distribution centres and meat processing facilities.

Andrews said if transmission of the virus continued in workplaces, health authorities may make a list of which industries are and are not essential for people to be in the office.

“And that could cause enormous damage, even more than this virus already has done,” he said.

Sutton said abattoirs, aged care homes and distribution centres were common places where the virus was spreading and it would be mandatory for everyone in those workplaces to wear a mask.

In response to the months-long spread of coronavirus in aged care settings, the Federal Government has announced it will supply one million masks to aged care facilities throughout Victoria, and a further million masks to disability carers.

Five testing teams will also be set up in nursing homes across metropolitan Melbourne and Mitchell Shire, and federal funding will be provided to residential and home care providers to make sure staff do not work across multiple sites.

Regional Victoria’s case numbers are growing

The virus is continuing to spread into regional Victoria, with an extra 10 cases reported since Wednesday.

The latest regional statistics show there are 45 active cases outside Melbourne and Mitchell Shire.

The City of Greater Geelong sits on the fringe of the lockdown area and now has 11 active cases, while Golden Plains, Macedon Ranges, Horsham and Greater Bendigo each have four.

The Australian Medical Association’s Victorian branch president, Julian Rait, said he would like to see compulsory mask use expanded to some regional areas.

“The AMA’s been calling for [mandatory mask use] for some weeks, the reason being early last month The Lancet published a meta-analysis saying the virus could be stopped by two-thirds or more by mask use,” he said.

NSW border residents will be subject to stricter restrictions on travelling into the Victorian side of the border zone.

If they travel beyond the border zone and further into Victoria, they will have to quarantine for 14 days when they return home.

Anyone with a permit to cross the border will have to reapply for it from Wednesday, and will only be issued the permit if they need to cross the border for work, education, medical care or health supplies.

Victorians are also facing further restrictions on travel to South Australia.

The South Australian Government has declared Tasmania, Queensland, the Northern Territory and Western Australia “low community transmission zones”.

Everyone outside those zones entering SA must be tested for coronavirus within 24 hours of arrival and on day 12 of their quarantine, or face a $1,000 fine.

The rules are retrospective and include everyone arriving from Victoria, NSW or the ACT since July 8, except essential travellers and children under 16.

With Victorians unable to get around the rest of the country, Prime Minister Scott Morrison has announced the August 4 sitting of Parliament has been cancelled.

The announcement came after acting Chief Medical Officer, Paul Kelly, said allowing politicians to come to Canberra was a significant risk due to increased community transmission of the virus in Victoria and NSW.

-AAP, additional reporting by ABC / Rachel Clayton