Evacuees will be flown out of China on a Qantas passenger plane and could leave Wuhan in the early hours of Monday morning.

A scheduled Qantas plane leaving Sydney for Hong Kong on Friday night will stay there waiting for the green light from Chinese officials to enter Wuhan.

Evacuees will be flown back to Darwin first before being transported on to Christmas Island in smaller aircraft.

Medical specialists will spend the weekend preparing a quarantine facility on Christmas Island for the Australian evacuees.

Experts from Australia's disaster response team were dispatched to the island on Friday.

The nation's top health bureaucrats have not yet recommended suspending all flights from China but the Transport Workers Union is calling on the government to do so.

"The federal government must take urgent action to protect its own citizens and to help prevent a potentially devastating global pandemic," the union said.

The World Health Organisation has declared the disease, which has killed more than 200 people in China and infected thousands, a public health emergency.

The declaration means there will be a greater focus on a global response, with WHO fearful of what could happen if the virus reaches countries ill-prepared to cope with high infection rates.

"Australia has been acting in advance of this decision," Prime Minister Scott Morrison said.

"All of the issues - isolation, case management, contract tracing, prevention of onward spread, active surveillance, early detection - Australia has been doing."

Human coronavirus with pandemic potential is a listed human disease under Australian laws, which enables the government to use "enhanced border measures" to contain outbreaks.

Australia's chief medical officer, Brendan Murphy, said the world would soon know if containment was realistic.

"It is not yet contained in China but they are making Herculean efforts to do so. It is contained very well in all the countries where it has been exported to, including Australia," he said.

The government's national security committee met on Friday to go over pre-planning and precautionary measures to battle the virus.

The virus has spread to 18 countries including Australia, which has had nine confirmed cases with more expected.

Hong Kong has closed its borders to mainland China.

"They are in a very different situation than an island nation like ours," Home Affairs Minister Peter Dutton told the Nine Network.

"We are not taking flights from Wuhan. And if we need to take further steps beyond that we will."

Mr Dutton again defended the government's plans to charge evacuees for part of the cost of their repatriation to Australia, and the decision to force them into quarantine on Christmas Island for up to two weeks.

He said costs had been applied to evacuees in the past, noting that not all the 600 or so Australians who had registered for the airlift would be evacuated.

Australian Associated Press