Chief medical officer Brendan Murphy said tonight there were 'signs of hope' that the restrictions already in place were helping to ease new virus infections.

"We've got an outbreak of 3978 cases at the moment, much less than some people might have predicted some time ago without mitigation. So there is evidence that the public health measures that we are putting in place and the social distancing measures are likely to be having some early effect," Dr Murphy said.

He rejected comparisons between Australia and countries where the spread has been most virulent such as the US, Spain and Italy.

"We have one of the highest rates of testing per head of population in the world and one of the lowest positive test rates so we think, unlike countries unfortunately like Italy, Iran and even the US, that when they detected significant outbreaks they probably had much, much larger outbreaks in the community that were undetected.

"We feel reasonably confident that we are detecting a significant majority of the cases in Australia. That means that we can get on top of cases when they are detected.

"As the Prime Minister has said, we have had a somewhat slowing of the growth in the epidemiology curve, but it is not enough. We have to slow it further.

"We have to slow it further and we have to stop the thing that's worrying us most, which is community transmission. That is transmission without known links to a known case. That is of concern, particularly in Sydney and to a lesser extent in Melbourne and South East Queensland. "