The casual nurse worked a single evening shift on Wednesday while infectious, NSW Health said.

"The nurse provided specialised care to a single patient, and had limited contact with a very small number of colleagues," it said in a statement on Saturday after issuing a public alert about the case overnight.

NSW Health's Dr Michael Douglas said the nurse is believed to have acquired coronavirus outside hospital and the second local case was linked to the nurse.

In the reporting period to 8pm on Friday, there was also one overseas-acquired case - a crew member who arrived in the Port of Newcastle from Brisbane on a ship with international mariners aboard.

"This case is receiving medical care at John Hunter Hospital," Dr Douglas said.

"All other crew members are considered close contacts and remain on board for quarantine and monitoring.

"It is important to note this case presents no COVID-19 risk to the people of Newcastle."

Meanwhile, the verbal joust between state governments over the NSW-Queensland border closure continues.

NSW Premier Gladys Berejiklian and Health Minister Brad Hazzard have criticised Queensland's 28-day "border clock" to trigger free passage between the states.

On Saturday, Queensland Health Minister Steven Miles defended his government's policy.

"I note that yesterday the premier of NSW expressed disappointment in my remarks, that they had given up on the effort of achieving 28 days of unlinked community transmission," he told reporters.

"Frankly, when she said she thought that was unattainable, when she said she thought that was impossible, I took that to mean that they were not aiming for it."

Although the number of tests undertaken in NSW increased to 15,439 in the latest 24-hour reporting period, from 12,868 in the previous 24 hours, NSW Health is concerned about the recent drop in testing.

It repeated its call for people to be tested if they have mildest of symptoms like a runny nose or scratchy throat, cough, fever or other symptoms that could be COVID-19.

NSW Health put out a new alert on Saturday afternoon about confirmed cases of COVID-19 who attended venues in Sydney's west and southwest during the week.

It says anyone who attended Squeeze & Grind in Camden from 11.45am to 1.15pm on Wednesday or Narellan Town Centre from 12.30pm-2pm on Thursday must monitor for coronavirus symptoms and get tested immediately if they develop them.

NSW Health issued the same warning for passengers on two trains between Eastwood and Parramatta on Wednesday, and five trains departing from or arriving at those two stations on Thursday.

NSW Health is treating 56 cases, including one in intensive care who does not require ventilation.

Eighty-four per cent of cases being treated by NSW Health are in non-acute, out-of-hospital care.

The latest cases take NSW's total to 4084 and the death toll remains at 55.

Australian Associated Press