The NSW premier has warned that COVID-19 case numbers may "go up considerably" after the state recorded 18 new local infections.
Some 130 people have now picked up the virus locally since June 16, when the case of an unvaccinated limousine driver was reported at Bondi in Sydney's east.
While the tally was significantly lower than the 30 cases in the previous 24-hour period, Gladys Berejiklian said the NSW public needs to brace itself.
"We have to be prepared for the numbers to bounce around and we have to be prepared for the numbers to go up considerably," Ms Berejiklian told reporters on Monday.
The numbers won't decline for at least another five days, according to Chief Health Officer Kerry Chant.
A city-wide lockdown was called on Saturday afternoon after cases started seeping out of Sydney's east into other areas.
Dr Chant said relief would only arrive when all new cases were linked and already in isolation.
Of the 18 cases recorded in the 24 hours to 8pm on Sunday, six were in isolation for their entire infectious period and three were isolated for part of their infectious period.
But half of them were not in self-isolation at all and were moving around in the community.
Westfield Bondi Junction remains one of the venues singled out by NSW Health as of particular concern.
Anyone who was there, including in the car park, between June 12 and 18 must get tested for the virus.
Four other venues - Lyfe Cafe at Bondi, the Joh Bailey hairdresser at Double Bay, Great Ocean Foods in Marrickville and The Royal Bondi - are also key venues.
Any visitors to those venues at various times in the last two weeks are dubbed close contacts.
Those venues, plus scores more listed by NSW Health as exposure sites, have sent thousands into isolation.
Additional alerts were added on Monday afternoon for Domino's Pizza Merrylands, Glenquarie Hotel in Macquarie Fields and Black and Gold Espresso in Rosebery.
Dr Chant on Monday reminded people in isolation they should be cocooned away from others even in their home, wearing a mask while around others and using a separate bathroom if possible.
"If you are a close contact, don't think 'I am vaccinated' or 'I was really only there for a few minutes'. Please follow the health advice and stay in for the 14 days," she said.
More than 500 school students from South Coogee Public School are also isolating after four of their classmates acquired the virus.
Another student, at Emanuel School in Sydney's east, attended school whilst infectious, Dr Chant said.
Meanwhile, the NSW government is urging eligible residents to get vaccinated amid evidence it was providing good protection against the Delta variant.
Health Minister Brad Hazzard said that just over 30 people attended a West Hoxton "super-spreader" birthday party.
Of the attendees, 24 unvaccinated people acquired the virus while six fully vaccinated healthcare workers escaped infection, as did a partially vaccinated aged care worker.
Monday marks the second full day of a two-week hard lockdown for the Greater Sydney, Central Coast, Blue Mountains, Wollongong and Shellharbour regions.
Millions of people in the lockdown zone can only leave home for work that can't be done at home, to shop for essentials, for exercise, to seek medical care and for care-giving, or compassionate reasons.
Anyone in regional NSW who has been to Greater Sydney since June 21 is also required to stay home for the lockdown period.
The Australian Retailers Association earlier this week estimated the loss in retail trade during the lockdown would reach $2 billion.
Woolworths and Coles, meanwhile, have established purchase limits in NSW for toilet paper amid panic buying of the product.