A raft of shutdowns and cancellations began, with sporting codes, schools, movie theatres, workplaces and more taking unprecedented steps to limit contact between people. States of emergency were declared in the ACT and Victoria, as a compulsory two-week quarantine began for anyone arriving from overseas, with hefty fines of up to $11,000 for anyone who doesn't comply in NSW.

More measures will be considered on Tuesday, including rules covering gatherings in enclosed spaces, such as pubs.

Prime Minister Scott Morrison returned to Canberra on Monday night from where he is preparing to announce measures to help industries hit hard by the coronavirus crisis, just days after announcing plans to pour $22.9 billion into the economy.

In NSW, cases jumped to 171 by Monday morning. Nationally, the number of cases passed 330.

"This is a war against a virus that knows no boundaries," NSW Health Minister Brad Hazzard said. "It is starting to look as if there will be a substantial, what some would understand to be an exponential, increase in numbers over the next few weeks."

Despite increasing community transmission - 44 of the NSW cases were from local transmission with another 60 of unknown source - testing is still being limited to people who have been overseas or in contact with a confirmed case.

Deputy Chief Medical Officer Paul Kelly says Australia has problems sourcing "consumables" for testing kits, and will continue limiting testing to overseas cases or contacts.

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Professor Kelly would not say how many tests were available in Australia, but he said the issue was not with the kits themselves, but with the consumables used in the kits. He cited a case where a fever clinic tested almost 1600 people with just one positive, and said the decision had been made to focus testing on where "you get best bang for your buck".

"We have to look at very carefully and how we're doing the testing where we're doing the testing. And yes, that has put some strain on some of these consumables in the laboratory. I won't go into details, but there are many things in a laboratory that are needed other than tests," he said.

"... This is not surprising, but we're looking at ways that we can deal with that."

Nor would Professor Kelly provide details on whether Australia had sufficient ventilators, with supply proving a problem overseas. He said health authorities were looking to "dampen demand" for ventilators and to source them across Australia and New Zealand.

He emphasised that 80 per cent of people who contracted coronavirus would not need to go to hospital, let alone end up in intensive care, let alone even then requiring a ventilator.

Last week, NSW Chief Health Officer Kerry Chant told estimates hearings that the state was working on an infection rate of 20 per cent of the population, with 5 per cent of infected people needing intensive care and 1 per cent dying. It appears Dr Chant was using national modelling, and ACT Health Minister Rachel Stephen-Smith has confirmed the same figures would apply in Canberra.

That would mean 84,000 Canberrans infected, with 4200 requiring intensive care, and 840 deaths.

The national modelling has not been released, beyond Dr Chant's figures.

On Monday, Professor Kelly was asked about German Chancellor Angela Merkel's figure of 60 per cent of the population infected, and Dr Chant's figure of 20 per cent.

"It's something in that range," he said. "I'm not going to speculate on the actual numbers. But this is an infectious disease, the more we can do to separate people and to stop that infection spread the better," he said.

Asked about the death rate, he said it was "around 1 per cent - you do the maths".

If 20 per cent of Australians are infected, that's about 5.1 million people, with 51,000 deaths.

As the Reserve Bank is preparing emergency financial measures to help an economy devastated by massive shutdowns, Mr Morrison is finalising a support package for industries in trouble, including airlines, hospitality and tourism.

Air travel is being drastically scaled back, international tourism is grinding to a halt, and concerts, sports events and other gatherings are cancelled, in measures that will see significant job losses and could bring many industries to their knees.

Mr Morrison met Treasurer Josh Frydenberg and Finance Minister Mathias Cormann on Monday and on Tuesday night will meet the state and territory chief ministers, who are gathering as a new national cabinet.

Former prime minister Kevin Rudd accused the government of complacency and acting too slowly.

On public health, the government's public information campaign on personal hygiene, social separation and community events ... has been several weeks too slow," he said, writing in the Guardian.

"Its messaging has also been contradictory on basic things like handshaking and public events."

Reports emerged on Monday that two people who shared a flight to Los Angeles with Home Affairs Minister Peter Dutton had tested positive to coronavirus. Professor Kelly said he was confident Mr Dutton was not infectious on the flight, but he might have contracted the virus on the flight.

"Whether he caught it on the plane or before that it's hard to know," Professor Kelly said. "We know that the incubation period for this particular virus is quite long - it can be up to 14 days, but mostly five to six days. He'd been back in Australia for six days by the time he became sick. So he was not infectious on that plane."

Mr Dutton flew to Los Angeles on the flight with the women who now have coronavirus on March 4. He returned on March 8; they arrived back on March 14.

Mr Dutton tested positive to coronavirus on Friday March 13. It is possible he contracted the virus on the March 4 flight, or while in the United States.

In the US, he met Donald Trump's daughter Ivanka Trump and other senior officials in the Trump circle, but health authorities in Australia insist he would not have been infectious before Wednesday March 11, so are focused only on the 24 hours before he started showing symptoms. Mr Dutton attended a cabinet meeting on Tuesday March 10 in Sydney, but his Cabinet colleagues are not considered at risk despite the cabinet room being scrubbed by people in hazmat suits on the weekend.

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