Two people in NSW were cleared on Friday, while a further two in the state and another pair in Queensland are being assessed for the virus which originated in the Chinese city of Wuhan.

Australia's chief medical officer Brendan Murphy said testing processes for the virus have matured.

"The laboratories now believe that they can get an answer which is good enough to act on within the same day now," he told reporters in Canberra on Friday.

There are no confirmed cases of the virus in Australia.

NSW chief health officer Dr Kerry Chant said the state's patients had been isolated and did not pose a risk of transmitting the virus that has so far killed 26 people in China.

"We're encouraging people who have come back from Wuhan, or who have been in contact with confirmed cases in China or in other countries, to please seek care if you develop any symptoms of fever, sore throat, pneumonia, a cough or respiratory symptoms of any sort," Dr Chant said.

Two of the suspected cases in NSW were cleared on Friday afternoon.

Queensland's Chief Health Officer Dr Jeannette Young said four tests in the state have come back negative.

"'We've got another two suspects at the moment that we're assessing who may need testing," she said.

Of the 844 cases reported worldwide, 830 are in China and Prof Murphy expects more to occur around the world, but stressed it's "very hard to predict".

"We suspect that we'll see increasing numbers of cases for some time," he said.

Biosecurity experts met the first plane from Wuhan to Sydney on Thursday and found no ill passengers but warned symptoms could take a week to emerge.

Airports worldwide are screening passengers arriving from China, while Taiwan has banned anyone from Wuhan from going to the island.

Crossbench senator Rex Patrick has called for all direct flights from China to Australia to be screened by biosecurity staff.

China has put millions of people in lockdown in an attempt to curb the virus from spreading while the 11 million residents of Wuhan have been told not to leave.

Health officials fear the transmission rate could accelerate as hundreds of millions of Chinese travel at home and abroad for the Lunar New Year, which begins on Saturday.

Scientists are beginning work on a vaccination for the virus, with a team of Queensland researchers one of three teams around the world hoping to find a medication within six months.

The previously unknown virus strain is believed to have emerged late last year from illegally traded wildlife at an animal market.

Australian Associated Press