There have been four new confirmed cases of coronavirus in New South Wales, while a doctor working at Sydney's Ryde Hospital has been revealed as one of two people diagnosed on Monday.

Key points: Four new cases have been announced for NSW, bringing the total to 13

Four new cases have been announced for NSW, bringing the total to 13 It includes the first case to have involved a traveller from Singapore

It includes the first case to have involved a traveller from Singapore One of the cases is a 39-year-old man who travelled from Iran

Staff who had worked with the 53-year-old doctor, who was the one of the first person-to-person transmission of coronavirus in Australia, have been put on leave and patients were being contacted.

NSW Chief Medical Officer Dr Kerry Chant said he had been working with the "usual sort of patients we have, which is a diverse range of patients on our system".

The doctor is being treated at Westmead Hospital.

The new cases announced on Tuesday include a 53-year-old man who recently travelled to Singapore, as well as a 39-year-old man who travelled from Iran who came via Kuala Lumpur and Singapore.

The 53-year-old man is the first case in NSW that appears to have come directly from Singapore.

NSW Health Minister Brad Hazzard, speaking at a press conference on Tuesday. ( ABC News )

Two other cases have also been confirmed on Tuesday afternoon, NSW Health Minister Brad Hazzard said.

Two women, both in their 60s who returned to Sydney from South Korea and Japan, have tested positive.

Mr Hazzard said there was no information as yet on any flight details concerning the women.

There have been 13 cases in NSW to date

"We are seeing quite an escalation of diagnoses of the virus," he said.

"Having said that, the people who have been diagnosed in the last little while today in the latest pathology runs have all had a fairly positive position in that they were diagnosed in the early stages."

No further information was given about the doctor due to privacy issues and to avoid any "disincentive" for people needing to seek healthcare, Dr Chant said.

He had not been working with any known coronavirus cases, she said.

She said staff working in "close contact" were on leave and in "precautionary isolation".

Extra staff had been brought in to cover those in quarantine, she said.

Patients seen by the doctor were also being informed by telephone, she said, with advice on a case-by-case basis depending on when they saw him.

"The message has to be tailored for each individual patient when they were exposed [to the doctor], what the health advice is," Dr Chant said.

Information is being gathered around the travel details surrounding the latest cases.

NSW Health was also looking into new year celebrations which will take place within the Iranian and Azerbaijani communities on March 20 and may involve large-scale events.

'Practise social distancing'

Federal Government chief medical officer Brendan Murphy has said the two cases of transmission on Australian soil were "very isolated" and there is no evidence of widespread community transmission.

"If you have come back from South Korea or Italy or Iran, then we would certainly want you to practise some social distancing, not go to mass gatherings," he said.

On Monday, Mr Hazzard had recommended that people cease handshaking in Australia.

Dr Chant said there is no widespread transmission of the virus in NSW.

"We have to remain vigilant but, even if occasional cases are missed, if people practise good hygiene, do common sense things, then the likelihood of transmitting it, even if someone is unaware they had it, is reduced," she said.