With COVID-19 outbreaks on either side of the Murray River, key surveillance of wastewater has ramped up.
NEW does testing at Wangaratta, Benalla, Yarrawonga and Wodonga - a passive sampler is dropped into the inlet infrastructure before wastewater progresses to treatment.
The sample, after collecting particles, is couriered to Melbourne where it is analysed for viral fragments.
It is after this point that data reaches the desk of Albury Wodonga Health's public health unit.
"As you would imagine, it goes from the water to testing labs to data systems, to people checking," physician Rod McClure said.
"It's highly technical, but at the end of the day it's highly personal; there's nothing we can do to solve this problem without the people of Victoria coming with us."
Dr McClure said with the emergence of the NSW outbreak, samples on the border were increased to twice-weekly and then thrice-weekly.
"It can be increased or decreased, and in areas along the Hume Highway, we want to make sure we've got some background surveillance," he said.
"We do depend upon the people coming forward to be tested, and when we get detection in the wastewater of some viral particles, that allows us to indicate to that local community they should be a little bit more vigilant.
"Our unit is part of a networked response across Victoria - we can decide where we need to swing our efforts, and obviously with the situation that we're facing both within and outside of the state ... hence the the numbers of wastewater tests have been increased."
More than 13,000 wastewater samples have been tested in Victoria since August, 2020.
An unexpected detection may be due to someone who has had COVID-19 but is no longer infectious continuing to 'shed' the virus, or it may be due to an active but undiagnosed infectious case.
People who have had COVID-19 may shed the virus or virus fragments on used tissues, off their hands and skin when washing, and in their stool.
Over time the virus breaks down and small pieces of the virus (called 'viral fragments') can enter wastewater through toilets, bowls, sinks and drains, and then travel through the sewer network.
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People can shed the virus for several weeks after their infectious period.
"Victorians are encouraged to get tested if they have mild symptoms to help our efforts to detect and contain outbreaks at the earliest possible stage and keep Victorians safe," A Department of Health spokesman said.