While the tests worried health authorities, they say there have been no recent cases in the area.
According to the working definition, a state or territory has achieved elimination of community transmission of coronavirus if it goes 28 days with no mystery cases, a period which represents two long incubation cycles for the virus.
University of Melbourne epidemiologist Tony Blakely said new cases will almost certainly leach back into the community as a result of international arrivals and hotel quarantine breaches. But he said the state’s contract tracing program has been improved so dramatically they pose less of a threat than at the outset of the pandemic.
“It was a bit of a longshot to actually get all the way to elimination,” he said, “I’m pleasantly surprised that we’ve been able to bring it back from that high point.”
Professor Blakely said the milestone was a “huge tribute” to Victoria’s Chief Health Officer, Professor Brett Sutton, and his deputy Professor Allen Cheng. “They are the masterminds of this,” he said.
“When we got down to 10 [cases] per day, it was stubbornly there, I thought this might be our new reality.”
He said the key to reaching elimination was fixing Victoria’s contract tracing efforts in Melbourne’s northern suburbs so that small outbreaks could be quickly shut down.
“I used to say that quarantine wasn’t rocket science, I’ve had to modify my view – this virus is so sneaky,” he said.
Melbourne will start to receive international arrivals again on December 7, with Mr Andrews confirming the state will stick with a modified version of its original hotel quarantine program.
The Premier ruled out a home-based isolation scheme for low-risk travellers, as was recommended by the state’s hotel quarantine inquiry, but said Australians returning to Melbourne will be required to be tested for coronavirus before they board a flight.
The last patient in Victoria infected with the virus, a man aged in his 90s, was discharged from hospital on Monday night, after being admitted last month. The man was treated at the Monash Medical Centre for more than 40 days alongside his wife who also contracted the virus.
Victoria achieved its first “triple doughnut day” on Tuesday, with no new coronavirus cases, no deaths and no active cases, for the first time since February 29.
There have been 20,345 cases of COVID-19 in Victoria and 819 deaths, most of them among the elderly in aged care.
Deputy Chief Health Officer Allen Cheng said on Thursday that the results from the Corio treatment plant were unexpected as there have been no recent COVID-19 infections in the area where the viral fragments were found.
The positive result could be from a person who has recovered from the virus and is living in the area or visited and is still “shedding” the virus.
“We have had few of these positive wastewater results recently and, while we haven’t discovered any undiagnosed case of coronavirus, it is possible that there may be an infectious person in this catchment,” Professor Cheng said.
“We encourage people in this area who are symptomatic to be tested and will update the community once more testing results become available. It is also a timely reminder for local businesses to re-check their COVID Safe plans to keep themselves, their colleagues and customers safe.”
Last week, viral fragments were found in wastewater samples from Altona, Benalla and Portland. No cases have been detected in those areas following the findings.
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David Estcourt is a court and general news reporter at The Age.