A COVID-shedding Victorian man who returned to the regional town of Colac is the likely source of a positive wastewater sample.
The Department of Health and Human Services put out a testing call for locals and visitors to the Colac area, southwest of Melbourne, after revealing viral fragments had been detected in a treatment plant sample from November 23.
Testing commander Jeroen Weimar believes they may have found the source, with Barwon Health identifying a former case who is back in the area.
The man has had a "significant tail" of shedding the virus, Mr Weimar said, and wasn't infectious en route.
"We know they've moved back into the area and they're likely to be a significant source of that positive that we saw last night," he told reporters on Wednesday.
Despite his presence potentially explaining the positive sample, Mr Weimar is keen to continue to drive up testing numbers in Colac.
"I'm very pleased that we've made the connection to this individual," he said.
"Nevertheless, we know that Colac is a town of 15,000 people. If there's anybody in that town who's not feeling well, we still want them to come forward and get tested.
"We are doing some more work in Colac over the coming days looking at some of the major employment sites to make sure we've really run this one to ground."
A similar notice was issued to residents of Geelong's northern suburbs last week after traces of coronavirus were detected in Corio wastewater.
Portland, Benalla and Altona also produced positive samples last month, but turned up no new positive infections.
Mr Weimar said the wastewater testing program was expanding to include new sites at Bayswater, Lilydale, Upper Yarra, Wallan, Whittlesea and Healesville.
"I expect to have 60 sites up and running in the next week or so," he said.
It comes as an expert panel ruled a woman in her 20s isn't a new case after she initially recorded a weak positive test result on Monday.
The young woman was placed in isolation pending the result of a third test, which came back negative on Tuesday.
Victoria has recorded 33 days without a virus case.
Premier Daniel Andrews says announcements will be made on Sunday about what restrictions will look like for the state over summer.
"That will be good news for many people right across Victoria," he said.
"It will mark a really important phase as we lock in a set of rules for a few months, for that COVID-safe summer."
There were 12,177 Victorians who came forward for testing on Tuesday, as Queensland and South Australia reopened their borders to the state and Western Australia confirmed it would too on December 8.
"If we want to retain those freedoms, we have to ensure that any of us who feel symptoms - no matter how minor - please do go and get tested," Mr Weimar said.
