Close contacts from the Port Melbourne coronavirus case that visited Axedale will be retested for the virus following viral fragments being detected in Bendigo's wastewater.
Department of Health deputy secretary Jeroen Weimar said the 189 close contacts were already in quarantine and had already returned negative tests during that period.
"We have had 189 primary contacts from Axedale and Bendigo (in quarantine) for (almost) two weeks," he said.
"Most contacts have passed their day 13 retest which were negative and are being released. There are a small number of people still to go and we are working with through those people Bendigo Health."
Traces of the virus were found in Bendigo's wastewater Wednesday night.
Mr Weimar said virus fragments appeared in wastewater from time to time across a vast majority the state
He said there were two explanations why fragments would be detected in wastewater.
"One is we have got someone newly incubating a COVID-19 case," he said. "The last flare up, we retested all the Axedale contacts. We will retest the remaining Axedale contacts through their day 13 tests and keep sampling waster.
"If there is no sustained pattern (of the virus) in the wastewater, it will mean someone who previously had an infection is shedding the virus or someone with the virus was passing through."
Mr Weimar said wastewater testing couldn't completely determine if the fragments came from a new case or recovered case.
"Wastewater testing is a sensitive tool. It is a bit of a canary in a coal mine. It doesn't 100 per cent tells is if it is a newly incubated case or if someone who had COVID is still shedding the virus," he said.
"But we use it as a way to drive testing activity and to remind people to get tested if they show symptoms."
Health minister Martin Foley said the detection of viral fragments in Bendigo's wastewater wouldn't necessarily mean restrictions would stop easing.
"We have been down the path with viral fragments before but not in Bendigo with so many personal close contacts," he said. "If we re-target those personal close contacts and get repeat of negatives, that will be reassuring.
"The message to the wider Bendigo area and people who have been through there is to check your symptoms and, with the slightest one, please come forward for testing.
"There are no plans to (stop easing restrictions) at the moment. If we can put this call out and do lots of testing and it comes back negative, it gives the public health teams assurance the virus is not out out there in the community and that it is someone shedding."
Mr Foley said the wastewater testing result in Bendigo concerned the north and north-western suburbs.
"Testing has detected pings of COVID where there are currently no confirmed cases," he said. "While it is not completely uncommon to have people who have previously had COVID to shed the virus for months, the other explanation is an undiagnosed infectious case.
"In that that regard, have we missed a strain of transmission somewhere. We hope that is not the case. Or is this a historical shedding from many weeks or months ago? Or was it from someone who was passing through (the area)?"
Mr Foley said people who were in areas including California Gully, Eaglehawk, Epsom, Huntly, Jackass Flat, Madien Gully, Marong, North Bendigo and Sailors Gully between the dates of June 3 and 7 to monitor their symptoms.
"We are really keen that people in that part of Bendigo monitor their symptoms and get tested if they get any slight symptoms," he said. "This helps shape the public health advice in the careful and cautious easing of restrictions. Clearly, we are still currently running down these outbreaks and it isn't over yet."
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