A quarter of workers in high-risk industries will be randomly tested for coronavirus each week as part of Melbourne's plan to emerge out of lockdown.
Premier Daniel Andrews on Wednesday announced all medium and large businesses in meat, poultry and seafood processing, and in the supermarket and distribution sectors, will be asked to test 25 per cent of their workforce weekly.
Workers are encouraged to head to one of the state's 200 testing sites from Thursday.
Those without symptoms won't be required to self-isolate while they wait for their result.
"These businesses know and understand this is in their interests and it's in everyone's interest right across the whole state to have that sense of monitoring," Mr Andrews said.
"This thing can simmer, it can be out there and not necessarily be obvious to you."
Regular testing will also occur in aged care after an agreement was struck with the federal government.
About 50 per cent of workers at metropolitan Melbourne aged care facilities and 25 per cent in regional Victoria will be tested weekly.
The federal government will test all private aged care staff through a private provider.
Wastewater will also continue to be monitored at more than 30 sites across Victoria.
Jeroen Weimar from the Department of Health and Human Services confirmed a COVID-positive sewerage sample was identified at Anglesea, despite the area having no known active cases.
"We know there is either someone who has had coronavirus in the Anglesea area or someone who has passed through, but it may also be someone who is not yet aware that they have the virus," Mr Weimar said.
He encouraged anyone in the Anglesea area "who has any symptoms whatsoever, who feels remotely unwell" to get tested. A testing site has opened at Anglesea Town Hall.
It comes as Victoria has recorded 13 new coronavirus cases and four more deaths on Wednesday, bringing the state's death toll to 798 and the national figure to 886.
The latest victims are a woman in her 70s, a woman in her 80s and a man and woman in their 90s.
Two of the four deaths are linked to outbreaks in aged care facilities, where 147 cases remain active among residents and staff.
Of the 13 new cases, two are household contacts of aged care staff from Estia Keilor and Edenvale Manor in Keilor East.
Another two cases are linked to a worker from the Butcher Club at Chadstone shopping centre.
The worker was contagious between September 23 and 26, when they worked 6am to 6pm shifts at the butcher and used public toilets in the vicinity.
The Butcher Club, Coles Chadstone, Chadstone shopping centre fresh food precinct and Woolworths Ashwood have been added to the high-risk coronavirus hot spots.
Victoria's Chief Health Officer Brett Sutton said the worker's close contacts are self-isolating.
"If you've been in the vicinity of these areas on these dates and times, if you've got any symptoms whatsoever, please come forward and get testing and isolate," he said.
Despite the slight increase in new cases, which Professor Sutton said was common on Wednesdays, Melbourne's 14-day is average down to 16.4.
There remain 21 mystery cases in Melbourne between September 14 and 27.
Melbourne's 14-day average needs to drop below five and there must be fewer than five mystery cases for a fortnight before the state eases restrictions further.
The premier said this was not likely to happen until October 19.
"We are so close to seeing this off," he said.
There are 44 Victorians fighting the virus in hospital, including six in intensive care, three of whom are on a ventilator.
Australian Associated Press