NSW has 48 hours to determine the source of three new locally transmitted coronavirus infections if there's any hope of Queensland's border reopening on November 1.
After 12 consecutive COVID-free days NSW Premier Gladys Berejiklian delivered the disappointing news that Thursday's numbers would include the new infections, detected overnight after the official tally ended at 8pm.
"It's not a surprise ... and my expectation is that will happen again," the premier told reporters on Wednesday.
"We're always going to have cases pop up because we're in a pandemic, but we're also in an economy that is open, where people are undertaking their business, where we don't have [closed] borders but for Victoria.
"We're managing it well, but we will never be out of the woods until there's a vaccine."
None of the three cases - a Camden woman, a Parramatta woman and a Wollondilly man - are linked to each other.
NSW Health are racing to trace contacts and have issued a number of public health alerts.
Anyone who attended an 8.15am pilates class at Fitness First in Carlingford on October 3 is considered a close contact and must immediately get tested and isolate for 14 days, even if the test result is negative.
Anyone who wasn't in the class but visited the gym between 8am and 9.15am is considered a casual contact and must monitor for symtpoms.
People who attended the following venues are also considered casual contacts:
* Narellan Kmart on October 2, between 6pm and 7pm
* Penrith Homemaker Centre on October 4 between 11am and 1pm
* Penrith Guzman y Gomez on October 4 between 1.30pm and 2pm
* Penrith Home Co on October 4 between 2 pm and 2.30pm
* Westfield Parramatta on October 5 between 9.30am and 11am
* Castle Towers Shopping Centre on October 5 between 12pm and 1pm
Queensland Premier Annastacia Palaszczuk says even a single case of untraced community transmission in NSW would reset the border clock countdown.
She has said the border would reopen on November 1 only if NSW had 28 days with no locally transmitted "mystery" cases.
Queensland Health Minister Stephen Miles told reporters it was too early to say if the 28-day countdown for border reopening would have to be reset.
"We will monitor very closely whether NSW can link those cases to existing clusters," he told reporters.
"We hope they can ... the public health units will provide the contact tracers with 48 hours to identify that link."
Earlier Ms Berejikilian again implored her Queensland counterparts to reconsider their "unrealistic" stance.
"I say to the Queensland government, I appreciate you will probably come out today and say the 28 days is ticking from the start. Until the end of the pandemic, it is unlikely that NSW will get to 28 days with no community transmission."
NSW Health said that in the 24 hours to 8pm on Tuesday three returned travellers in hotel quarantine were diagnosed with COVID-19.
It remains concerned about low testing rates, with the past two days coming in at under 6000 when at least 8000 people should be tested every day.