Fragments of the virus that causes COVID-19 have been detected in a sewage network in Sydney's Inner West.
NSW Health tweeted on Friday it was located at a site in Homebush which services a catchment area that includes 40,500 people.
The Homebush site takes sewage from the suburbs of Homebush West, Strathfield, Rookwood, Concord West, Sydney Olympic Park, Wentworth Point, Newington, Lidcombe, Homebush, Silverwater, Petersham, Liberty Grove, Rhodes, North Strathfield and Concord.
"NSW Health is aware of recent COVID-19 cases, several returned overseas travellers, who live in this catchment," a tweet said.
"People who are recently recovered from COVID-19 can continue to shed virus fragments into the sewerage system for several weeks even after they are no longer infectious.
"Nonetheless, NSW Health is asking everyone in the area to be vigilant in monitoring for symptoms, and if they appear, get tested and isolate immediately until they receive a negative result."
No new cases in NSW
On Friday, NSW recorded no new cases of the coronavirus in the state.
That includes no new locally acquired cases in the 24 hours to 8pm last night as well as no new cases acquired overseas.
The total cases in NSW since the beginning of the pandemic remains at 5,378.
NSW Health tweeted the last time there were no new cases in the state in a 24-hour period was on April 1.
There were also 14,691 tests reported to 8pm Thursday night, just shy of Wednesday's total of 16,178.
"NSW Health is treating 51 COVID-19 cases, one of whom is in intensive care and being ventilated," it tweeted.
"Most cases (96 per cent) are being treated in non-acute, out-of-hospital care, including returned travellers in the Special Health Accommodation."
Fragments detected in sewage last month
In April, coronavirus fragments were found in sewage systems at Allambie Heights in Sydney’s north.
It was the second time Covid-19 fragments were detected in this system after they were also found earlier last month.
More than 80,000 people use the system which services suburbs including Manly, Collaroy and Narrabeen.
NSW Health said it could signal undetected cases in the community and added people should be on alert for any cold-like symptoms including sore throat, runny nose, cough, fever, loss of taste or sense of smell, or headache.
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