An expanded lockdown now covers 5m people in Greater Sydney, as well as the Blue Mountains, Central Coast and Wollongong.
Cases of the highly infectious Delta variant now stand at 110.
NSW Premier Gladys Berejiklian said on Sunday that she expected that figure to rise.
"Given how contagious this strain of the virus is, we do anticipate that in the next few days, case numbers are likely to increase even beyond what we have seen today because we are seeing that people in isolation, unfortunately, would have already transmitted to all their house contacts," she said.