South Australia has recorded another three cases of coronavirus, taking Australia to 200 confirmed cases.

Key points: SA's Premier announced the latest three coronavirus cases this morning

SA's Premier announced the latest three coronavirus cases this morning The latest to test positive are two women, aged in their 30s and 80s, and a man in his 50s

The latest to test positive are two women, aged in their 30s and 80s, and a man in his 50s All three had recently been overseas to countries including the US and the UK

SA Premier Steven Marshall made the announcement this morning following an emergency SA Cabinet meeting.

The latest cases include a woman in her 30s who had travelled from the UK and a man in his 50s who had been in the US.

The third new case was a woman in her 80s who had both been overseas and in contact with another confirmed case.

South Australia has recorded a total of 19 cases, including a student at Sacred Heart College who tested positive yesterday.

"Six of the people who have been affected have already passed through this illness and have been discharged from hospital," Mr Marshall said.

"We have 13 people who are currently isolated, most of those within our major hospitals."

Mr Marshall attended yesterday's COAG meeting, along with his interstate counterparts and Prime Minister Scott Morrison, during which it was decided mass gatherings of more than 500 people would be cancelled.

A national cabinet comprising state and federal leaders has also been established to coordinate responses to the spread of COVID-19.

"We're asking people who are unwell not to come to work. We're asking people to adopt and abide by this norm in terms of social distancing," Mr Marshall said.

"We don't want to be using finite resources to test the 'worried well'."

Mr Marshall said Home Affairs Minister Peter Dutton — who was later diagnosed with coronavirus — was not at Friday's COAG meeting.

"We certainly haven't received any advice that we are in a cohort that should be tested," Mr Marshall said.

Isolation debate breaks out after Dutton diagnosis

Mr Dutton attended a Federal Cabinet meeting alongside colleagues on Tuesday, and Labor has criticised the Government's response to Mr Dutton's diagnosis.

"The Government has advised that they don't need to be tested or self-isolated because there was no immediate contact in the 24 hours prior to symptoms emerging," Opposition health spokesman Chris Bowen said.

"The public advice and guidance to people who have close contacts with a confirmed case says nothing about any 24-hour period, it simply says that anybody who has been in close contact should be self-isolated."

But the nation's chief medical officer Brendan Murphy — who also attended Tuesday's Cabinet meeting attended by Mr Dutton — said there was no need to place himself in quarantine.

"No member of Cabinet was in contact with Minister Dutton within 24 hours of him becoming symptomatic, nor was I in fact in contact with him," he said.

"If there had been a requirement for quarantine, [the Prime Minister] was insistent that Government and Cabinet follow those rules."

The number of cases globally has reached 140,000, and the World Health Organisation this week declared a pandemic.

"We have early evidence of community transmission, mostly in New South Wales but a little bit in other states. We have moved quite early to institute social distancing measures," Professor Murphy said.

"We have made the decision early enough so that we can give people a few days' notice to start on Monday, so we can have an orderly transition."

Health authorities seek better access to flight manifests

South Australia's chief public health officer Nicola Spurrier said one "difficulty" had been in speedily accessing flight manifests to notify passengers who had been near those infected.

"We've been working with the other states to try and improve the speed with which we can get the manifests," she said.

"The people we are really wanting to be able to contact very quickly are the people who are sitting two rows ahead and two rows behind and to the side."

Dr Nicola Spurrier said accessing flight manifests was taking too long. ( ABC News: Simon Christie )

A-League side Adelaide United today postponed matches involving its National Premier League (NPL) and NPL reserves teams.

The club said a player had been placed in isolation "as a result of attending Sacred Heart College".

The Adelaide Symphony Orchestra has also cancelled its weekend Gustav Mahler concerts, because a member may have been in close contact with someone who has coronavirus.

The Australian Medical Association (AMA) has questioned the decision to delay the cancellation of major public gatherings until Monday.

"I would advise all my vulnerable patients in the community to make a decision and consider whether they should attend and whether they, rather than waiting for Monday, make that necessary step now," president Tony Bartone said.

Dr Spurrier said while she intended to go to an event this weekend, she urged those who felt unwell to exercise caution.

"We haven't closed any of the Fringe events or other events this weekend, but if anybody is sick — if anybody has a cough, a fever, a runny nose, starting to feel unwell, a bit of a sore throat — please do not go to any of these public events," she said.