Of the 65 new cases in the 24 hours to 8pm on Wednesday, at least 35 people were out in the community for part or all of their infectious period.
For this reason, Premier Gladys Berejiklian warned on Thursday that the number of daily infections was likely to again rise in the coming days.
"Whilst the case numbers are bouncing around, we are seeing a stabilisation ... they are not growing exponentially," Ms Berejiklian told reporters.
"That tells us that the settings that we have in place are having an impact. My strongest message to everybody is keep doing what you are doing."
There are 19 people in intensive care in NSW, with five ventilated.
Five million NSW residents will ensure at least another fortnight of lockdown after a run of high daily coronavirus numbers forced the state government on Wednesday to extend stay-at-home measures to at least July 30.
Meanwhile, Prime Minister Scott Morrison says relief is on its way for parents in locked down Greater Sydney, who will no longer have to pay for childcare they're not using.
The measure could benefit around 216,000 families across 3600 centres.
Infection numbers continue to rise in southwest Sydney and a new 24-hour Covid testing clinic has opened at Fairfield after people were forced to wait up to six hours in long queues at another venue.
There are now three testing sites in the area operating around the clock.
The clinics were inundated on Wednesday after new health orders were introduced requiring essential workers to get tested every three days if they work outside the area.
Two of Sydney's major hospitals are also on high alert after a nurse and a patient were both diagnosed with Covid-19.
A pregnant patient at Liverpool Hospital, in Sydney's southwest, was diagnosed on Wednesday after undergoing a procedure.
The hospital cancelled elective surgery to deep clean the operating theatre and contact tracing is underway with close contacts - including staff - being tested and isolating for 14 days, NSW Health said.
A nurse who worked at Westmead Hospital in the Covid-19 ward has also tested positive for the virus but there were no cases linked to the health worker so far, the ABC reports.
Queensland extends mask mandate
Queensland authorities are racing to avoid another lockdown after three locally acquired cases of Covid-19 emerged in Brisbane.
Premier Annastacia Palaszczuk says the three cases include a 12-year-old boy who flew into the state from Sydney on July 9 and his father.
A fully vaccinated Brisbane Airport worker has also tested positive, which is a major concern for authorities.
Ms Palaszczuk says a face mask mandate due to end on Friday for 11 local government areas will be extended for another seven days in a bid to avoid a lockdown.
"I am sure everyone is sick and tired of wearing masks, they are uncomfortable, but they are extremely important and if everyone continues doing it, coming forward and getting tested, then hopefully we won't be required to go into a lockdown," she told reporters
"That is the thing that we all absolutely want to avoid."
The mask mandate will be in place until July 23 in Brisbane City, Logan, Moreton Bay, Ipswich, Redlands, Sunshine Coast, Gold Coast, Noosa, Somerset, Lockyer Valley and Scenic Rim.
Chief Health Officer Jeannette Young said the boy had travelled to the US and arrived back in Australia via Sydney Airport on June 21 with his mother.
He quarantined for 14 days there before flying with his mother to Brisbane on Qantas flight 544 on Friday.
The boy is believed to have given his father the virus after arriving home at Newport on Brisbane's Bayside. The mother has tested negative so far but is now in hospital with her son.
Dr Young said it's uncertain whether the boy picked up the virus in hotel quarantine in Sydney or elsewhere.
The father worked at an office on the Sunshine Coast on Wednesday, but Dr Young believes the family have not visited many other venues in the southeast.
Dr Young said the third case in a female airport worker is more concerning because she is fully vaccinated with Pfizer, and worked three night shifts on Monday, Tuesday and Wednesday while infectious.
"I don't know exactly where they work at the airport, we will have to go through all of that and work out where she's been," she said.
The woman, who lives at Tarragindi in Brisbane's south, visited Woolworths Annerley from 10.36am till 11.36am on Monday and Chemist Warehouse in the same suburb from 8.39am to 8.49am on Wednesday.
The chief health officer is waiting for genomic testing to find out what strains of COVID-19 the three cases have contracted, and where they picked up the virus.
"I'll get confirmation later today, but I suspect they are unrelated to all of our other cases, these are new outbreaks," Dr Young said.
