Victorian daily case numbers are continuing to fall, and in NSW there were four new cases to 8pm yesterday.

NSW Chief Health Officer Kerry Chant said a number of factors would go into her decision to allow free movement into the state.

"The sorts of things we'll be looking at are the testing levels in Victoria, the level of locally acquired [cases] - where the person was not in isolation," she said.

"As the numbers come down, the information we're getting from Victoria is much-improved, and I'd like to also extend my appreciation.

"When we've had some cases more recently in the border communities, where we've had to work together, we've worked together excellently.

"We want to see the effect of easing restrictions as well.

"At the moment, the number of contacts they would have for every case, given the lockdown, is very low.

Dr Chant was asked if she would like to see the effect of increased movement post-lockdown in Melbourne before providing advice about lifting the border closure.

"It's one of those factors we consider ... as you ease restrictions, what do you see?" she said.

"We're obviously very watchful about regional Victoria; clearly there's been a number of controls put in place to prevent people moving from Melbourne to rural Victoria.

"As we know, no border or controls are ever fool-proof."

Premier Gladys Berejiklian said the high testing rates in NSW and contact tracing teams had kept the virus suppressed so far, but movement around the state would heighten the risk.

"We just want people to make sure ... if you feel the onset of the mildest symptom, please get tested," she said.

"We know that during the school holidays, families, understandably, will be moving all across NSW.

"This is happening at the same time we're easing border restrictions .. there's more people coming across.

"We're going into a bit of a high-risk period."

IN OTHER NEWS:

Ms Berejiklian said keeping the border shut to Melburnians and opening the border up to everyone else was among the alternatives being considered.

"It's not so much a number, it's really about how many unknown cases there are and what the trends are," she said.

"We don't want to leave the borders up any more than we need to.

"Our health experts ... have been sharing data more and more and that helps us with our assessments.

"Apart from the Victorian situation ... the rest of Australia has absolutely no reason to have any borders between us."

Of the new cases in NSW, three were returned travellers in hotel quarantine, and one new case was a person already recognised as a close contact and who was already in isolation.