The announcement comes as Byron Bay was placed on high alert after five out of eight of Queensland's new COVID-19 cases recorded today attended a party at the popular holiday spot at the weekend.
She said of the hens party which involved the two positive cases who visited Byron Bay, one is a NSW resident but is now staying in Queensland and is being tested there.
Premier Gladys Berejiklian said she "would not be surprised" if infections were detected in NSW.
"Until the end of Easter, four local government areas will be subject to some restrictions".
"Continue to monitor for symptoms and if they appear, get tested again", NSW Health said.
Queensland's second-largest hospital started turning away all but the most critical patients on Wednesday morning. She had received the first of two vaccine jabs.
"This additional lockdown will enable PA Hospital to put in place processes to manage impacts associated with these linked cases", an official said.
Chief Health Officer Dr Kerry Chant said the man who became infected was at the pub with three of his friends.
"She was tested as part of the asymptomatic screening testing process for that ward and was found to be positive", she said.
"So we just need to work out how she got it".
There are now 2.5 million people in a three-day lockdown in Greater Brisbane, however it is still uncertain whether the lockdown will be lifted or extended over Easter and also be expanded to the Gold Coast.
Today's update follows speculation over whether millions of Brisbane residents will remain in lockdown through the Easter long weekend, with one infectious disease expert, associate professor Paul Griffin of the University of Queensland, expecting an extended lockdown to be announced tonight.
Queensland Premier Annastacia Palaszczuk and the state's health authorities are due to decide on a possible extension of the lockdown this evening, but previously warned a further escalation of cases could see the directive pushed back.
"That is a massive, massive number".
"At this point, all I can say to those people who might be intending to attend and to the organisers themselves, which I have expressed to them personally, but to those who might be intending to come, just be alert to the messages that will come from the New South Wales Government in the next 12-24 hours as we look at the unfolding situation on the north coast". "Probably. Probably, we will see more".
"[But it's] absolutely critical that we rule out any unlinked community transmission of COVID in our community".