The shift in focus comes amid mounting concerns that an outbreak could be disastrous for Pacific island nations, especially Australia's closest neighbour, PNG.

PNG has so far confirmed just one coronavirus infection (an expatriate later evacuated to Australia and later found to be negative) but public health specialists and development workers caution that PNG's high rates of poverty, poor nutrition, threadbare health services and pre-existing health problems such as tuberculosis mean the country of eight million is highly vulnerable to the disease.

Lowy Institute's Pacific Islands Program director Jonathan Pryke said there were only about a dozen ventilators in Port Moresby and only a couple in other parts of the country.

Mr Pryke said the country's health system was already stretched to the limit dealing with serious endemic health problems including malaria, tuberculosis and diabetes.

Ann Clarke, project manager for the non-government organisation Businesses for Health: TB and HIV, said an outbreak of Covid-19 in PNG, particularly in Port Moresby and other large centres, would be "an absolute catastrophe".

Dr Clarke said respiratory problems and diseases such as tuberculosis, pneumonia and asthma were prevalent, accounting for a third of the country's total health burden.

The most recent available data show that in 2018 there were 37,000 active cases of tuberculosis alone, resulting in 4700 deaths.

Dr Clarke warned that if there was community transmission of Covid-19 in the country, the health system would quickly become overwhelmed.

She said there were only about 100 intensive care unit beds across the entire country, and Port Moresby General Hospital was "already full of TB patients".

The PNG Government has declared a 30-day state of emergency, and for the next two weeks all incoming international and domestic passenger flights have been grounded, schools have been closed and non-essential workers are required to stay home.

In the National Capital District, which includes Port Moresby, shops remain open but public transport has been shut down.

Health workers warn many have little capacity to abide the social distancing and hygiene measures considered essential to slow the disease's spread.

Water Aid PNG country director Rachel Payne said in settlements in major urban centres like Port Moresby and Lae it was not uncommon for up to 15 people to live in a house, and access to water was very limited.

Ms Payne said 60% of people lack access to safe water and just 2 per cent have somewhere in or near their home where they can wash their hands.

Dr Clarke warned of the risk of "bodies in the streets" if PNG failed in its attempts to stop the community spread of Covid-19.

Mr Pryke said the move by Mr Morrison to raise the plight of Pacific island nations at the G20 was a "positive sign", but cautioned that PNG alone would need much more than $22 million.

He said a large portion of Australia's $1 billion of aid to the region would need to be re-purposed to the Covid-19 response.

Aid to the Pacific has been attacked by critics who argue that the Australian government should focus its efforts on the country's needs first.

But Mr Pryke said it was in Australia's own interests to be part of politically stable and healthy neighbourhood.

China has also increased the pressure on the Australian government to increase its efforts in the region.

In what Mr Pryke described as "a remarkable pivot", the Chinese are offering to provide medical materials and expertise to countries preparing for or grappling with Covid-19, opening a new front in the contest for influence in the region.

"Australia has really planted a flag here with its [Pacific] Step-Up initiative and that should resonate in good times and bad," he said. "This is where you show your resolve. We should be true to our word on this stuff."