No new COVID-19 cases have been detected in NSW but Gladys Berejiklian is bracing for some to emerge after two infected people visited the northern tourist haven of Byron Bay.

"We hope that we do not have any cases arise in NSW but I would not be surprised if we did, so we must brace ourselves," the premier told reporters on Tuesday.

NSW is on high alert for new cases after a number of venues in Byron Bay were visited by two women from Queensland last weekend who were infected with the highly-contagious UK
strain of the virus.

From Thursday the popular beach resort town is due to host the five-day Bluesfest over the Easter long weekend with up to 16,000 participants every day.

Greater Brisbane has begun a three-day lockdown after a coronavirus cluster that's now grown to 15 cases, sparking fears of significant community transmission.

"We are expecting more cases [linked to] Queensland and hopefully most of those cases will be people in isolation or although we have to assume this is an evolving situation," Ms Berejiklian said.

Anyone who had been to Queensland since March 20 needed to comply with the lockdown rules there.

The state's borders are still open but "if cases are identified in NSW, we will have to respond. I'm hoping it doesn't come to that", she said.

Meanwhile, the premier is urging people in NSW to "please change your plans" if they intended to travel to anywhere in Queensland for the Easter break, warning there was a chance they could end up trapped in a lockdown.

"There's no better place to holiday than NSW," she said.

Ms Berejiklian is also urging everyone in NSW to check in at every venue, socially distance and sanitise hands.

"I cannot stress enough the importance of being COVID-safe," Ms Berejiklian said.

"And most importantly, if you've attended any of the venues NSW Health has identified, get tested, stay home and isolate for the full 14 days," the premier said.

Chief Health Officer Kerry Chant said NSW Health had contacted 1321 people who attended the Byron Beach Hotel last Friday asking them to isolate and get tested.

And 166 people who visited The Farm last Sunday have also been contacted and asked to test and isolate.

Anyone who has returned from Brisbane from March 11 should be on high alert for symptoms, she said.

Anyone who has even mild symptoms should get tested and stay home and isolate until further advice.

NSW Health is advising people who had travelled to Queensland or Byron Bay to check each state's websites for information about venues they have visited.