Covid 19 coronavirus: Thousand of Sydney residents urged to get tested after traces found in sewage

Despite no new reported cases of Covid 19 in NSW, traces of the virus have been found in the wastewater. Photo / File

Nearly 20,000 Sydneysiders have been asked to urgently present for testing after traces of coronavirus were found in the wastewater.

Almost 20,000 residents living in Sydney's northwest have been urged to get tested after fragments of Covid-19 were found in sewage across two locations.

Health authorities sent out an alert on Wednesday night explaining virus fragments had been detected at two sewage pumping stations in Western Sydney, which serve several suburbs.

"The area served by one of the pumping stations includes a population of around 5860 residents of North Kellyville and Rouse Hill," NSW Health said in the statement.

"The second pumping station serves a population of around 12,650 people across the suburbs of Rouse Hill, Box Hill, The Ponds, Kellyville Ridge, Parklea, Quakers Hill and Acacia Gardens."

The fragments were detected through the state's ongoing sewage surveillance programme.

While findings could reflect older cases of the virus, NSW Health said it is "concerned" there could be other active cases out there in the community and residents could "incorrectly assume" their symptoms indicate a common cold.

A new pop-up clinic has been established in The Fiddler car park, on the corner of Windsor and Commercial Rds in Rouse Hill, in preparation for a testing blitz.

NSW has recorded four straight days of zero local cases.