Four cases of the deadly coronavirus have been confirmed in Australia, as authorities scramble to contact passengers who shared flights from China with the patients.
Three men tested positive to the respiratory condition in NSW on Saturday, state health authorities confirmed.
It comes after another man, aged in his 50s, tested positive in a Melbourne hospital after arriving from the Chinese city of Guangzhou last week.
A total of 18 people have been tested for the virus in NSW, with 12 of those given the all-clear.
Nine people in Queensland have returned negative results for coronavirus, with authorities on Saturday still waiting on results from another possible case.
Four people in South Australia were also being tested but authorities said it was unlikely they actually had the virus, with a man also being checked in a Hobart hospital.
The first confirmed Australian case involved a man who had been in Wuhan, the city of 11 million people at the epicentre of the outbreak.
He flew from Guangzhou to Melbourne on China Southern Airlines flight CZ321 on January 19.
The man has pneumonia and is in a stable condition in isolation at the Monash Medical Centre.
Passengers from the same flight are being contacted as a precaution, while all arrivals from China are being stopped at airports and given information about symptoms and what to do if they feel unwell.
"He did not show any symptoms whilst he was on the flight so it's possible he wasn't contagious but there's a lot we don't know about this virus at this point," Victoria's Health Minister Jenny Mikakos told reporters.
The man had taken precautions by phoning ahead and wearing a mask to his GP and then the hospital, where he was admitted on Friday.
In NSW, two of the men travelled to Sydney from Wuhan and the third from China's southeastern Shenzhen.
NSW Chief Health Officer Kerry Chant said it was a matter of when, not if, the virus would arrive in Sydney. She confirmed one man arrived in Australia on January 6, another arrived 13 days later and she was yet to confirm travel details for the third man.
Forty-one people have died from the coronavirus in China out of more than 1300 cases.
The illness has been confirmed other countries including Thailand, Japan, South Korea, Hong Kong, Singapore, France and the United States.
Australians are being urged not to travel to Wuhan or China's Hubei province.
The Department of Foreign Affairs and Trade has listed the virus as having "pandemic potential". This allows for enhanced border protection measures.
Experts are still learning about the virus and Australia's Chief Medical Officer Brendan Murphy says it's important people arriving from Wuhan, as well as those in close contact with them, look out for symptoms of fever, cough, sore throat, vomiting and difficulty breathing.
"We don't know exactly how long symptoms take to show after a person has been infected but there is an incubation period and some patients will have very mild symptoms," Prof Murphy said.
Prime Minister Scott Morrison says the confirmation of cases in Australia had been expected and procedures were in place to manage the situation.