Traces of COVID-19 have been detected in raw sewage across Sydney as part of new research that could provide another tool in the fight against the pandemic, NSW Chief Health Officer Kerry Chant says.
She said the sewage testing program by NSW Health and Sydney Water could show where the virus had been and provide early warning in places without known or recent cases.
The research tests for molecular markers of SARS-CoV-2, the virus that causes COVID-19.
"This is early days for this research, and we have a lot of work to do analysing our findings, but it's one more way we can strengthen our fight against COVID-19," Dr Chant said in a statement.
"This is a program that will show us where COVID-19 has been. For instance, we would expect to see viral fragments in Sydney sewage where we have consistently had cases in the community or in hotel quarantine
"However, if we continue to have very few active cases, there is scope for this testing to provide early warning in places without known or recent cases."
The first round of samples found positive results at Bondi, Malabar and Winmalee. Further analysis is needed to assess the significance of these results.
Sydney Water's General Manager Customer, Strategy and Engagement, Maryanne Graham, said treatment processes effectively deactivated the virus and there was no risk to testing staff.
She said Sydney Water was also supporting NSW Health by analysing samples from regional areas including the Hunter, the North Coast, Southern and Western NSW.
NSW health officials have again urged people to get tested urgently when COVID-19 symptoms appear, with residents increasingly moving about the state during school holidays.
NSW recorded no locally acquired cases on Saturday after a mystery infection on Friday ended a three-day run without community transmission.
Just a single case was identified in the latest reporting period - a returned traveller in hotel quarantine - from more than 12,000 tests.
Even so NSW Health stressed that getting tested "right away at the earliest symptoms" remained vital, especially in Sydney's southwest.
Friday's local case was a man in his 50s from that area but who had not had contact with a previously confirmed case.
There are concerns his infection could reset NSW's "border clock" with Queensland if authorities can't determine how he got sick.
Queensland chief health officer Jeannette Young says she will await the result of an investigation.
NSW must record 28 days with no community transmissions before its border with Queensland is reopened - a feat Premier Gladys Berejiklian says is a "pretty tall order".
That target was on track to be reached on October 6 but the case has put it in doubt.
People in Australia must stay at least 1.5 metres away from others. Check your state’s restrictions on gathering limits. If you are experiencing cold or flu symptoms, stay home and arrange a test by calling your doctor or contact the Coronavirus Health Information Hotline on 1800 020 080. News and information is available in 63 languages at .
