There have been no new locally-acquired cases of COVID-19 in NSW for the 11th straight day but the virus has been detected in two sewage plants.
Health officials say 11 cases were recorded in overseas travellers in hotel quarantine in the 24 hours to 8pm on Monday, bringing the total number of cases in NSW to 4057.
NSW Health's Christine Selvey on Tuesday urged people with symptoms, particularly in the Hawkesbury and southwestern Sydney, to get tested after sewage surveillance detected the virus at the North Richmond and West Camden treatment plants.
The most recent cases in the West Camden catchment were reported last month but no one living in the North Richmond catchment had recently tested positive.
"Virus fragments in sewage can mean active cases but people can continue to 'shed' virus genetic material for some weeks after recovery," Dr Selvey said Tuesday.
Meanwhile Premier Gladys Berejiklian is doubtful that NSW will go 28 days without community transmission - the benchmark Queensland Premier Annastacia Palaszczuk has set for the border to fully re-open on November 1.
She went on Sydney radio to say the requirement was unrealistic and there was no contingency plan if NSW recorded a case after that.
"If you apply that criteria: what's the next step?" Ms Berejiklian asked while speaking on Sydney radio WSFM's on Tuesday.
"Does that mean that they'll open the borders and we'll get a case and they'll close again? You can't live like that."
Ms Palaszczuk, who goes to the polls on October 31, told reporters she would take advice from her Chief Health Officer Jeannette Young on the matter.
""I think there'd have to be widespread community transmission ... but I think if we were starting to see what happened in Victoria, initially, then that would be a cause for concern."
"Dr Young .... takes into account testing rates, she takes into account sewage testing, but also too, the rates of community transmission. If there was widespread community transmission that would be problematic, but we're not seeing that at the moment in NSW so that's good news."
There were 5385 tests conducted in NSW in the 24-hour reporting period, compared with 4789 the previous 24 hours.
NSW Health remains concerned about the recent drop in testing, saying at least 8000 people should be tested in NSW each day.
NSW Health is treating 50 COVID-19 cases, including three in intensive care, none of whom are being ventilated. Eighty per cent of cases being treated are in non-acute, out-of-hospital care.