NSW Premier Gladys Berejiklian said five of the six cases were household contacts of yesterday’s positive case, a man in Western Sydney. The sixth was a close contact of yesterday's case.

She said the cases were close to the Western Sydney suburb of Berala, where a cluster has been linked to the BWS bottle shop.

However genomic testing was underway to determine whether the cases were linked.

NSW chief health officer Kerry Chant said one of the cases worked at Concord Repatriation Hospital on January 12, 13 and 14 in the cardiology and radiology wards.

However, the worker wore a face mask during each of their shifts, their close workplace contacts had tested negative and the affected wards had been cleaned.

"I just want to reassure people that, please continue to access care from Concord. There is no ongoing risk to patients or staff there," Dr Chant said.

Ms Berejiklian urged the public to get tested after only 12,764 tests were conducted in the latest reporting period.

She warned testing numbers needed to increase for the government to have confidence to ease restrictions.

"New South Wales Government won't impose a restriction a day longer than we need to but our ability to ease restrictions does rely on the science and the health advice and we need to make sure we do it at the right time," she said.

"We're still confident that if testing rates stay high, that the health advice will give us that confidence to make those changes. But it does rely on more people coming forward to get tested.

"All of us want to be confident we can go back to what we had before Christmas and that will only be possible if we get those high rates of testing to give our … health experts confidence that we are on top of any unknown strains of the virus."

Ms Berejiklian said average rates of testing had been "outstanding" over the past few weeks.

"But we really need to up the ante."

Dr Chant urged people particularly in the suburbs of Bankstown, Lidcombe, Auburn, Berala and Wentworthville to get tested in order to "mop up any last chains of transmission".

She said traces of COVID-19 had also been detected in sewage in Glenfield, which covers some areas where cases had occurred.

However, she urged people in Ambervale, Appin, Campbelltown, Casula, Ingleburn and Minto to also get tested.

A health alert has been issued for the Wentworthville Medical and Dental Clinic in Station Street, Wentworthville.

Anyone who was in the dental, physio and imaging waiting room on Friday, January 15 between 11:30am and 1:15pm is considered a close contact and must immediately get tested and self-isolate for 14 days, regardless of the result.

People in other areas of the clinic at that time should monitor for symptoms and immediately isolate and get tested if they appear.

An alert was also issued for Auburn Centrelink, which was visited by a COVID-19 case on January 14, between 3:00pm and 4:14pm.

Anyone who visited at the time is advised to monitor for symptoms and, if they occur, get tested and self-isolate until receiving a negative result.

Alerts were also issued for several train services between Warwick Farm and Auburn on January 14 and 15.

Story By | Bellinda Kontominas