There are concerns about a growing COVID-19 cluster at a Sydney nursing home with five residents infected, amid reports a third staff member has the virus.

NSW Health Minister Brad Hazzard says the state is on "high alert" after the state recorded 35 new infections but insists there's no particular benchmark in the number of new COVID-19 infections that has to be reached before Sydney can emerge from lockdown.

There are concerns about a growing cluster at a Sydney nursing home where five residents have already tested positive, amid reports a third staff member has been diagnosed with the virus at the SummitCare home at Baulkham Hills in Sydney's northwest.

Greater Sydney is in the second week of lockdown with authorities refusing to rule out an extension of stay-at-home orders due to expire at midnight on Friday.

"Today will be very telling but I think hopefully we will be able to make some changes anyway," Mr Hazzard told ABC Radio National on Tuesday.

"We are certainly on high alert but we're also hopeful that we might be able to bring back some normalcy but we'll see how we go over the next couple of days," Mr Hazzard said.

The key to ending the lockdown was not just about the raw number of infections but whether cases were linked and whether or not there's unknown chains of transmission, he said.

"If we think there are cases out there that are still running loose so we don't know where they're coming from, that's very problematic," he said."

The two-week lockdown in NSW is expected to cost the economy around $750 million a week or more, according to St George Bank economists.

Brett Holmes, General Secretary of the NSW Nurses & Midwives' Association, says at least 500 nurses are in isolation after potentially being exposed to COVID-19 while working at Sydney's Royal North Shore Hospital.

Five wards have been identified as areas of exposure. Patients are being diverted to other hospitals, only urgent and emergency surgeries are going ahead at the hospital, and other nurses are being asked to work extra hours, he said.

"They were already working large amounts of overtime and often working short, so no doubt they're being asked to go further," Mr Holmes said.

"I'm not sure how they're going to sustain that."

At Fairfield Hospital, 120 health staff have been told to isolate, leaving others to work 12-hour shifts over the weekend.

Mr Hazzard said the crisis had put the system and staff under "enormous pressure" but with a total staff of 140,000, RNS was large enough to cope.

"That's pressure but it's not compromising patient safety," he said.

Meanwhile, 13 NRL St George players have been fined for attending a party at the home of Paul Vaughan on Saturday night.

NSW Police Deputy Commissioner Gary Worboys said he was dismayed by the behaviour of the footballers as well as people who attended a party in Waterloo in inner Sydney where three partygoers became infected.

"These sorts of things are the sort of events that will put everyone backwards so they're quite selfish and I think there's quite a bit of anger," he told ABC TV.

Elsewhere, NSW Health has issued fresh alerts for seven new venues, including a pharmacy at Belfield in Sydney's southwest and the Adventist Hospital at Wahroonga in Sydney's north.

And a stay-at-home order for people in NSW who had been in Brisbane and Moreton Bay, or who wish to enter NSW from those Queensland locations, has been lifted.

However, people who have been in Greater Sydney since June 21 must continue to follow the stay-at-home orders for 14 days.

Declarations are still required when people enter NSW after being in Queensland, Western Australia, the Northern Territory and Victoria.

People living and working in Queensland border areas who frequently enter NSW must now complete a declaration every 72 hours, instead of every 24 hours. The declaration confirms they have not attended a venue of concern as specified by Queensland Health.