Three new Wheatbelt COVID-19 virus cases, modelling says Australian health system will cope

They are among 22 new cases in WA, bringing the state total to 422 confirmed cases.

But Prime Minister Scott Morrison says the coronavirus infection rate is tracking in a way that will not overrun the country's health system.

Mr Morrison said authorities had been working on the modelling of expected infections in Australia, and would release the work on Tuesday.

It had shown that without the measures put in place 12 days ago, when venues were closed and social distancing rules imposed, infections would be double the current numbers, he said.

On Friday, Australia had 5274 cases. Mr Morrison said that would have been 10,500 without the partial shutdown.

"You're saving lives, you're saving livelihoods. And if you want to know how much, you only have to look overseas and see what is happening in other developed countries around the world," he said.

Mr Morrison said if measures stayed in place and intensive care capacity was boosted as planned, with extra ventilators, the health system would hold up.

"The trajectory is promising, it's encouraging," he said. "But there are no guarantees. This virus will write its own rules."