The hunt for hundreds of passengers that flew with man infected with coronavirus

NSW health officials are in the process of tracking down passengers who were on the same Sydney-bound flight as a man with coronavirus.

Four cases of the virus have been confirmed across the country, with a 50-year-old Victorian man revealed to be the first on Saturday morning.

NSW Health confirmed three other cases of the deadly virus found in men aged 35, 43 and 53 on Saturday night.

They remain in isolation in Sydney’s Westmead Hospital.

A China Eastern flight from Wuhan arrives in Sydney. It was one of the last planes to leave from the Chinese city that is now in quarantine. Source: AAP

Two of the men had travelled to the Chinese city at the centre of the outbreak - Wuhan - while another man had travelled from the southern city of Shenzhen but had direct contact with a person from Wuhan who was diagnosed with the virus.

The ABC reports that one of the confirmed cases developed symptoms the night he arrived in Sydney from China on Eastern Flight MU749, which landed at 11:35am on January 20.

NSW Chief Medical Officer Kerry Chant told the ABC they are in the process of tracking down other passengers from that flight.

A medical worker writes their colleague's name on a protective suit to aid in identification as they work at Zhongnan Hospital of Wuhan University. Source: AP

"We have asked the National Incident Room to pull the records for those people that were on the flight and we are getting the seat details,” he said.

Two more cases under investigation

NSW Health on Sunday said two possible coronavirus cases are under investigation - revised from four on Saturday.

Symptoms include fever, cough and difficulty breathing.

NSW Health Minister Brad Hazzard urged anyone with symptoms to come forward.

"Please be aware that we do now have coronavirus here in Sydney. If you've got symptoms, ask yourself whether you've come in recent weeks from China, particularly from Wuhan," he said on Saturday night.

Three cases of coronavirus have been confirmed in Japan, passengers can be seen wearing masks at Narita airport near Tokyo. Source: AAP

Mr Hazzard said the state's health department had done everything possible to identify and contain the virus. 

Australians are being urged not to travel to Wuhan or China's Hubei province.

Coronavirus: What we know so far

China has confirmed 56 coronavirus deaths, while 1,975 people are now estimated to have the virus worldwide.

The illness has been confirmed other countries including five cases in Thailand, three cases in Singapore, France, Japan, Taiwan and Malaysia, two cases in Vietnam, South Korea and the United States and one in Nepal.

Tourists wear face masks in France, where three cases of the Wuhan coronavirus have been identified. Source: AAP

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

China says the virus is mutating and can be transmitted through human contact.

The World Health Organisation says while the outbreak was an emergency for China, it's not yet a global health emergency.

Three research teams have begun work on developing potential vaccines, the Coalition for Epidemic Preparedness Innovations said. Scientists hope to be testing the first possible vaccines in three months' time.

—With AAP

Do you have a story tip? Email: newsroomau@yahoonews.com.

You can also follow us on FacebookInstagram and Twitter and download the Yahoo News app from the App Store or Google Play.