Western Australia has recorded another three cases of coronavirus, bringing the total number in the state to 17.

Key points: Three people aged from their 30s to 50s have tested positive

Three people aged from their 30s to 50s have tested positive Authorities say there has been no known community-based transmission

Authorities say there has been no known community-based transmission WA has a shortage of the laboratory reagent used in COVID-19 testing

WA Health Minister Roger Cook said the new cases included two men and a woman, all of whom had travelled overseas and who were now self-isolating at home.

Mr Cook said one of the three was not infectious at the time they travelled.

The three people are aged from their 30s to 50s and had travelled to the US, Canada and Jakarta in Indonesia.

It means WA's coronavirus tally has almost doubled in the last two days, with five new cases revealed yesterday.

The number of COVID-19 cases across Australia hit 200 earlier today when three more were confirmed in South Australia.

Health authorities in WA say they are conducting between 800 and 1,000 tests for coronavirus a day, from GPs and from COVID-19 fever clinics which opened in Perth earlier this week.

Mr Cook said there had been no known community-based transmission of the virus to date in WA.

"That's an important aspect of what we're trying to achieve here," he told reporters at a media conference in Rockingham with Premier Mark McGowan.

"Making sure that we can continue to control the speed and the scope of the spread of this virus as much as possible.

"Every day we do that we flatten the curve. We push out the peak of this epidemic and we reduce the number of people who'll be impacted by the COVID virus.

"That will mean the number of people who will require intensive care in the future will be lower. That's the name of the game at the moment."

More social distancing measures likely

The Minister warned there would eventually be community spread of the virus in WA, and — according to modelling by the Melbourne-based Doherty Institute for Infection and Immunity — between 2 and 25 per cent of the population would become infected.

Health Minister Roger Cook says hospital intensive care units are being prepared for the spread of the virus. ( ABC News: James Carmody )

Mr Cook said, of those, 2 per cent would be particularly badly infected, and the state's ICU capacity was being prepared for that.

He said social distancing measures would inevitably be increased.

Yesterday's meeting between Prime Minister Scott Morrison and state premiers saw an agreement reached to share medical supplies across the country, along with a recommendation against organised mass gatherings of more than 500 people.

WA is currently experiencing a shortage of the laboratory reagent used in testing for COVID-19, which in part prompted more stringent guidelines to decide who can be tested in WA.

WA's deputy chief health officer Robyn Lawrence said the state was still trying to secure more of the chemical reagent needed for testing for the virus.

Dr Lawrence said there was an acute global supply and WA had enough for the next seven days.

"We've got adequate supply for the next week and we're continuing to work with our suppliers to source more. We've got a really cooperative relationship and it's going well but there is a global shortage," she said.

Mr Cook said he was confident WA has sufficient supply of the reagent going forward to continue testing following assurances from the Commonwealth.

Australian Medical Association WA president Andrew Miller said in a tweet the state's hospitals were now full.

He said if there were many COVID-19 patients using ventilators, it could mean people with head injuries or who had suffered a heart attack would have no ventilator available.

"This disease affects everyone unless we stop gatherings now," he said.

Dr Miller said not enough has been done to slow the rate of infections.

He said universities should be shut from this week and schools from March 23, in a staged manner.

"We've not acted fast enough," Dr Miller said.

"We still have cruise ships coming into Western Australia this week, we still have flights coming in from overseas, and we believe — because we're not ready yet on the front line — we need to get that breathing space into the system by bringing forward strong consideration of closing those things down."

No WA school closures yet: Minister

Asked if schools would be closing, Mr Cook said that was a measure which could be triggered under the state's pandemic plan, "but we're not at that point yet".

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 3 minutes 56 seconds 3 m 56 s Will the coronavirus push Australia into recession? Alan Kohler takes a look ( Alan Kohler )

On Monday, Mr McGowan will join a national teleconference with the Prime Minister and fellow premiers to discuss the virus.

He will then convene a meeting of the Office of State Security and Emergency Coordination, which includes WA Police Commissioner Chris Dawson.

Mr McGowan signalled there could be new announcements as a result of those meetings.

"I want to make sure there is collaborative decision making, that we make decisions on behalf of the nation," he said.

A meeting of all directors-general of State Government departments is also scheduled to be held on Monday to plan further coordination, ahead of the Government's regular cabinet meeting.