Scientists have found sewage testing for COVID-19 can detect the genetic fingerprint of the virus up to three weeks before cases are reported through clinical testing of infected people.

Key points:The study confirmed wastewater tests detect the virus before infected people feel sickThe research was conducted using archival samples from February this yearWastewater testing has gained international recognition as an important tool in the pandemic response

The Australian-first study by national science agency CSIRO and the University of Queensland is hoped to enable health authorities to avoid full lockdowns in the future and instead safely contain small areas where outbreaks have occurred.

The early detection means the potentially deadly virus can be dealt with quickly, ahead of time, without health authorities having to test every individual.

CSIRO lead author Warish Ahmed said the analysis involved tracking genetic fragments of the COVID-19 virus that were flushed into the wastewater system through infected people’s faeces.

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The study showed the virus was detected in a Brisbane South wastewater treatment plant in late February 2020, up to three weeks before the first clinical case was reported and Australia’s international borders were shut.

‘We can outmanoeuvre this insidious virus’

CSIRO chief executive Larry Marshall said wastewater testing was one of the critical science-driven tools that would support opening borders to drive Australia’s recovery and reduce future disruption.

“Australians want to do the right thing, but this solution from science detects the disease before people feel the symptoms, so we can out-think and outmanoeuvre this insidious virus,” Dr Marshall said.

“It’s a true team Australia approach when states can stay open by targeting their response to contain the disease, saving whole regions from having to shut down.”

The tool provides an early warning of the disease spread through the faeces flushed into wastewater systems.

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It can be used in municipal wastewater treatment plants, or facilities such as aged care homes, student dorms, quarantine facilities, and passenger groups on international flights and cruise ships.

Published in Science of the Total Environment, the study confirmed the testing of wastewater detected the virus before people felt sick, as their bodies started shedding fragments of the virus into the wastewater system through their faeces before they knew they were infected.

The research was conducted using archival samples from February this year.

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Director of CSIRO’s Australian Centre for Disease Preparedness, Trevor Drew, confirmed people could become infected and spread or “shed” SARS-CoV-2 — the virus that causes COVID-19 — before they showed any clinical signs.

“Evidence has shown that this virus can infect people and replicate itself for some time before they start showing any symptoms, and some people are entirely asymptomatic but still shed the virus,” Professor Drew said.

“Like many other coronaviruses, SARS-CoV-2 replicates in our digestive system, as well as in our lungs, so it can be detected in effluent water a few days before enough people are clinically affected for us to detect the virus in people who are ill.”

Testing is conducted at a wastewater treatment plant.(Supplied: CSIRO)Study backs sewage testing’s use as ‘early warning system’

CSIRO’s Land and Water Science director Paul Bertsch said the research had reiterated the benefits of wastewater testing.

“The big opportunity is that it’s an early warning detection system for the virus in our community,” Mr Bertsch said.

“As we begin to open up our borders — both here in Australia and of course later on when we welcome international tourists and students back — having these early warning detection systems really provide the health professionals advance notice of where the virus is.

“That allows you to understand where you have to aggressively set up testing and tracking procedures and also if you do have to shut down. Instead of shutting down the whole area, you can just shut down where you see the hotspot emerging.”

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Wastewater testing has gained international recognition as an important tool in the pandemic response and has been used by Queensland Health since the outbreak began.

During the pandemic, it helped with positive detection in regions such as Ipswich, west of Brisbane, and Cairns in Queensland’s far north.

Just last month, the virus was detected at the Cairns North wastewater plant for a second week in a row.

The CSIRO said only two other studies had been published globally confirming the virus could be detected between one and four weeks before people showed clinical symptoms.

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