NSW Premier Gladys Berejiklian has warned more local cases are likely as the man, in his 50s, was very active in the community and had a high viral load.
Health authorities are scrambling to find out how the man contracted the coronavirus as he did not recently travel overseas and does not work in hotel quarantine or in a border or health role.
He also has not recently travelled interstate.
It is believed the man had been infectious since last Friday and Ms Berejiklian said they had to "assume there's other cases".
"Everybody in the state needs to be on high alert," she said.
On Thursday morning it was revealed NSW Treasurer Dominic Perrottet was self-isolating after he was identified as a close contact.
A Covid test has since returned a negative result, but in accordance with NSW Health instructions, the treasurer will continue to self-isolate for 14 days from last Friday.
Mr Perrottet was identified as a close contact after he visited the District Brasserie restaurant in Sydney's CBD on Friday April 30 between 11am and 12pm.
List of venues grows
The list of venues where the positive case visited continues to grow.
People who attended the following venues at the specified times are told to get tested and isolate immediately until NSW Health provides more advice.
Areas of concern on May 4:
Smith Made in Balgowlah - between 2.30pm and 2.45pm
Rug Cleaning Repairs Hand Rug Wash Sydney in Balgowlah - between 12.30pm and 1pm
Alfresco Emporium in Collaroy - between 1pm and 1.30pm
Woolworths in Double Bay - between 4.05pm and 4.15pm
Chemist Warehouse in Double Bay - between 3.45pm and 4pm
Areas of concern on May 3:
Azure Cafe in Moore Park - between 12.30pm to 1pm
The Stadium Club in Moore Park - between 11.30am and 12.30pm
The Royal Sydney Golf Club in Rose Bay - between 5.30pm and 9pm
Areas of concern on May 2:
The Meat Store in Bondi - between 3pm to 4pm
Areas of concern on May 1:
Barbeques Galore in Annandale - between 2pm to 3pm
Barbeques Galore in Casula - between 4pm and 5pm
BP Runway in Mascot - between 4.30pm and 5pm
Joe's Barbeques and Heating in Silverwater - between 1.30pm and 2.30pm
Tucker Barbecues in Silverwater - between 1.30pm to 2.30pm
Areas of concern on April 30:
Screening of The Courier at Event Cinemas in Bondi Junction - between 6pm and 8pm
Barbetta in Paddington - between 1.30pm and 2.30pm
Figo Restaurant in Rushcutters Bay - between 8.45pm and 11pm
District Brasserie in Sydney - between 11am and 12pm
HineSight Optometrist at Sofitel Sydney Wentworth - between 12pm and 1pm
NSW Health also reported on Wednesday evening fragments of the virus had been detected in the Marrickville sewage network.
The catchment includes about 42,000 people and takes sewage from Dulwich Hill, Marrickville, Summer Hill, Lewisham, Ashfield, Haberfield, Petersham, Lilyfield and Leichhardt.
"NSW Health is asking everyone in these areas to be especially vigilant in monitoring for symptoms, and if they appear get tested and isolate immediately until a negative result is received," NSW Health said in a statement.
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