About 225,000 people have been put on alert in the NSW Hunter region after fragments of Covid-19 was detected in sewage.
A sample was taken on Wednesday at Burwood Beach Sewage Treatment plant, which takes in the Newcastle City area and surrounding suburbs.
This new warning from NSW Health follows another issued on Saturday for areas covered by sewage systems at Allambie Heights and Merimbula.
"These positive sewage results may indicate the presence of people who have recently recovered from Covid-19, as they can continue to shed fragments of the virus for several weeks after recovery," a statement from the department read.
"However, NSW Health is concerned that they could signal undetected cases in the community, and asks people in these areas to be alert for any 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."
NSW suburbs impacted by the alert
Newcastle City area
No new local cases were reported in the past 24 hours to 8pm on Saturday, but there was an overseas acquired case.
NSW Health has administered 591 vaccines on Saturday, bringing the total number of inoculations to 553,866 in the state.
Western Australia battles Covid outbreak
People arriving in Sydney from Western Australia since 12.01am on Saturday are required to fill out a declaration form to confirm they have not been to an exposure site as listed on the WA Health website.
An outbreak in WA grew by one case on Saturday after a man aged in his 40s tested positive to Covid-19.
The news of the latest case came just hours after Premier Mark McGowan revealed there had been no additional community cases following a woman's infection identified to reporters on Friday.
Though the woman's case was reported on Friday, her case was reflected in Saturday's numbers, along with a returned traveller.
That woman in her 40s was a close contact of a 54-year-old man who completed quarantine in Perth, but later tested positive for the virus in Melbourne after spending several days in the Perth community whilst infectious.
The emergence of this man's case sent Perth into a snap, three-day lockdown which began on Saturday.
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