A 90-year-old woman died on Saturday with testing confirming she had COVID-19, NSW Health said in a statement on Sunday night.

She was a resident of the Dorothy Henderson Lodge aged care home where two other residents have died after becoming infected with the virus.

A 77-year-old woman has also died from coronavirus, the department said on Sunday.

The woman flew from Brisbane to Sydney on Friday, a Queensland Health spokesman told AAP.

She developed symptoms on the plane, was taken to hospital and died the same day.

NSW Health discovered the woman had contracted coronavirus and informed Queensland Health on Sunday, the spokesman said.

In a statement on Sunday NSW Health said it is "working with state health authorities to trace close contacts of the deceased woman".

"Our condolences are with the family and friends of both women at this time."

It comes as the number of coronavirus cases in NSW jumped by 22 over the 24 hours to 11am on Sunday, taking the total number of infected people in the state to 134.

The University of Sydney and the University of NSW confirmed separately on Sunday that a student from each of their institutions had been diagnosed with the virus.

Schools in NSW from Monday will adopt social distancing measures, including cancelling assemblies, excursions, and travel, as well as some events and conferences, NSW Department of Education Secretary Mark Scott announced on Sunday.

The provisions will also see all major sporting, arts and initiative events and activities temporarily stopped until further notice, including whole-of-school sporting events and inter-school events which involve three or more schools.

"The community expects schools to be as safe as possible. We are implementing these measures to provide peace of mind for students, parents and staff," Mr Scott said in a statement.

"Local inter-school sport and other activities, can proceed but we ask organisers to ensure that as far as possible, reasonable precautions are taken," he said.

"I trust our principals and staff to show leadership during this time."

The department is preparing for more closures if required through scaling up of technology, further staff training and preparation of off-site lessons.

It comes as all new jury trials in the NSW Supreme and District court will be suspended indefinitely from Monday.

Jury trials which have already begun will continue.

Prime Minister Scott Morrison announced on Sunday that from midnight all people coming to Australia will have to self-isolate for 14 days.

Under the NSW Public Health Act both state Health Minister Brad Hazzard and Emergency Services Minister David Elliott have the power to enforce these self-isolation provisions, premier Gladys Berejiklian told reporters in Sydney on Sunday.

"At this stage we believe that the provisions in the Public Health Act satisfy what we need to do," she said.

Mr Hazzard is currently "gazetting" provisions in the act to develop wording which could apply to self-isolation and a ban on mass gatherings of more than 500 people, which will both come into force on Monday.

"We do have enforcement provisions in relation to that self-isolation, but as you can appreciate that will be very difficult to monitor every single situation," Ms Berejiklian said.

"So there is a degree of having the public really support us in that as well, for people to do the right thing by the community, by their own family, and by their circle."

Police have already been called in to enforce one case of self-isolation, Ms Berejiklian said.

Australian Associated Press