A health alert has been issued for almost 100,000 people in Sydney and the NSW South Coast after Covid-19 was detected in sewage systems.
NSW Health said on Saturday morning it had been notified fragments of coronavirus had been found in sewage networks that serve Allambie Heights in Sydney's north, and Merimbula on the South Coast.
The Allambie Heights network covers 83,400 people in the Northern Head catchment across 17 suburbs and the Merimbula sewage treatment plant takes in 15,000 people.
"NSW Health is concerned that they could signal undetected cases in the community," NSW Health said in a statement.
It did note however the detection could be viral shedding from previous cases in the area.
The department added it was "concerned that they could signal undetected cases in the community, and asks people in these areas to be alert for any cold-like symptoms that could signal COVID‑19, including sore throat, runny nose, cough, fever or headache".
"If symptoms appear, please isolate and get tested immediately, and remain isolated until a negative result is received," it said in a statement.
Sydney suburbs included in health alert
North Curl Curl
Covid fears as Perth goes into lockdown
No new local cases were recorded in the past 24 hours from 8pm on Friday in NSW.
One new case was acquired overseas, bringing the total number of infections in the state since the beginning of the pandemic to 5230.
Australia's states and territories are bracing to find out how far local transmission has spread after a man who arrived in Perth from Shanghai on April 3 spent 14 days in quarantine, but was then active in the community for five days before leaving for Melbourne, where he tested positive for Covid-19.
As a result, residents in Perth and Peel regions in Western Australia went into a snap three-day lockdown overnight.
Meanwhile, people who arrive in NSW from Western Australia from Saturday will be obliged to comply with the same lockdown provisions.
NSW authorities encouraged anyone who has been in WA since April 17 to check the WA list of sites of concern and self-isolate if required.
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