NSW had reported no recent cases of locally transmitted COVID-19 through to 8pm on Tuesday night, for the 12th consecutive day.

However, overnight three reports of cases have been received, including two in South Western Sydney and one in Western Sydney.

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The cases were in the Campbelltown, Parramatta and Wollondilly local government areas.

Three cases in overseas travellers in hotel quarantine were diagnosed in the 24 hours to 8pm on Tuesday night, bringing the total number of cases in NSW to 4060.

"We did have a good run of 10 or 11 days, and my expectation is that will happen again," Ms Berejiklian said.

"My expectation is we'll be able to get on top of these three cases.

"This is a good reminder, a good wake-up call that we're living in a pandemic.

"We're managing it well, but we'll never be out of the woods until there's a vaccine."

The new cases were announced hours after Queensland Premier Annastacia Palaszczuk confirmed even a single case of community transmission in NSW would send it back to square one in its goal to have the border re-open.

She has said the border would re-open on November 1 only if NSW had 28 days with no community transmission of COVID-19.

"I would find it very surprising if we went for 28 days without community transmission... I would doubt that we would get to that number," Ms Berejiklian said.

Ms Berejiklian said on Wednesday that the three cases of community transmission received post-8pm last night are still under investigation.

"It's understood there isn't currently a link at all between the three cases, they're actually three separate cases," she said.

"All we know at this stage is there's no obvious link between the three cases, and there's no obvious link to existing clusters.

"We've said from the outset that the pandemic is evolving, and what we need to do in NSW is maintain that good balance of keeping the economy open, keeping all of us doing what we want to do, however with some restrictions in place to make sure that the virus doesn't get out of control.

"I believe in NSW to date we have struck the right balance, but that relies on all of us being vigilant, including maintaining social distancing and wearing masks if you're not maintaining social distancing.

"And also making sure that businesses do everything they can to comply."

According to NSW Health, there were 5970 tests reported in the 24-hour reporting period, compared with 5385 in the previous 24 hours.

NSW Health says testing numbers have dropped recently, which is a concern.

Therefore, NSW Health is appealing to the community to come forward for testing right away if they have even the mildest of symptoms like a runny nose or scratchy throat, cough, fever or other symptoms that could be COVID-19.

"This is particularly important due to the new cases reported overnight," they said in a statement.

"Testing is also important for people in the Hawkesbury and South Western Sydney areas, following yesterday's report that traces of virus were recently detected at two treatment plants: North Richmond in the Hawkesbury and West Camden in South Western Sydney."

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