Commissioner Mick Fuller says he understands the concerns given other states and countries have been let down by the hotel quarantine system.

"It's not lost on me how important it is," he told reporters on Wednesday.

"The current system is working but if it doesn't work I am accountable for it."

Mr Fuller noted NSW had taken on the "lion's share" of returned travellers - about 50,000 people - and audits of the system and the hotels were undertaken regularly.

If any security guards were found to not be up to scratch, they're removed from the program, he said.

"If we thought the cleaning or security or any other aspect needs to be enhanced, then we will do that," Mr Fuller said.

A Travelodge Hotel in Sydney was dumped from the quarantine program on Tuesday after an escalation in complaints about its cleanliness.

All 366 people quarantined at the hotel have been relocated.

Mr Fuller said two security guards who contracted COVID-19 didn't break any rules in their roles, but one - a 22-year-old Campsie man - was fined for not self-isolating while awaiting his test result.

Premier Gladys Berejiklian noted no system was foolproof.

"I wish other states would lift more of the burden because at the moment NSW is doing more than double all the other states combined," she said.

"I'm surprised the incidences we have seen in recent days have not emerged earlier because the job is massive."

NSW reported six new COVID-19 cases from 25,874 tests in the 24 hours to 8pm on Tuesday.

This includes one returned traveller in hotel quarantine and five which are locally acquired with the source not yet identified.

Chief Health Officer Kerry Chant said one of the new cases was a trainee bus driver who had limited contact with passengers and therefore posed little risk.

NSW Health said two of the new cases attended City Tattersalls Fitness Centre on Pitt Street on August 19, 21 or 23.

Anyone who attended the gym between 8am and 2pm on any of those days is considered a 'close case' and should be tested for COVID-19 and self isolate for 14 days.

One of the confirmed gym cases also visited Randwick's Royal Hospital for Women on August 25, including the Windscreens Cafe, which has since been closed for cleaning.

NSW Health advised that the hospital is working to contact all close associates of the case and that there is no ongoing risk to patients, staff or visitors.

One of the Tattersalls cases also worked at 300 George Street in the CBD on August 19, 20, 21 or 24 while infectious, and the Apple store in Broadway shopping centre was also exposed to the virus on August 22 between 3.40pm and 4.40pm.

NSW Health has asked participants of the 7.40pm Active Dance class at Virgin Gym Zetland on August 24 to get tested and self-isolate.

Meanwhile, three Sydney schools were closed on Wednesday due to possible COVID-19 cases among students at Riverstone High School, Wyndham College, and Schofields Public School.

A year 12 student had returned a positive result and three others will be re-tested for certainty.

There are 72 COVID-19 cases being treated by NSW Health with seven patients in intensive care and four ventilated.

Australian Associated Press