The first cases of person-to-person transmission of coronavirus have been confirmed in Australia.

Key points: Three new cases have been confirmed in NSW, two of which are human-to-human transmissions

Three new cases have been confirmed in NSW, two of which are human-to-human transmissions A 53-year-old frontline health worker in Sydney has contracted the disease

A 53-year-old frontline health worker in Sydney has contracted the disease A 41-year-old woman has contracted the virus from her brother, who recently returned from Iran

A 53-year-old health worker in western Sydney and a 41-year-old woman also in Sydney have contracted the virus without leaving the country.

NSW Health Minister Brad Hazzard said it was "particularly concerning" to have these two cases on NSW soil.

One other new case, a male in his thirties who returned from Iran on Saturday, was also confirmed this afternoon.

This brings the the total number of cases in NSW to nine.

The 41-year-old woman is the sister of a 43-year-old Iranian man who returned positive test results on Sunday. She has not travelled to Iran but was in close contact with her brother, who returned on February 22.

It was not known how the health worker contracted coronavirus but NSW Health said he had been working in direct contact with patients.

He has not travelled overseas for three months.

NSW Health has commenced investigations to determine which patients seen by the health worker need to be contacted and possibly isolated.

"There are no indications anyone else has contracted it from the doctor but NSW Health is taking every precaution," Mr Hazzard said.

"I stress that the Government here in NSW and the health authorities are being extremely transparent with the community as this unfolds."

All new cases are being treated at Westmead Hospital in Sydney's west, with the health worker being cared for in the intensive care unit.

'No handshaking'

Mr Hazzard said while there was no need for alarm and he would not be changing his daily routine, some discretion was still needed.

He has recommended people cease all handshaking.

"It's time Aussies give each other a pat on the back. No handshaking, it's not necessary."

"[And] I'm not going to say don't kiss, but you could be exercising a degree of care and caution with who you kiss."

NSW chief medical officer Dr Kerry Chant said the new case involving the health worker raises the question of whether a case has been missed in NSW.

She said while this is always a possibility, the public should be reassured there is no widespread transmission in NSW.

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

Health Minister Brad Hazzard (left) and NSW chief health officer Dr Kerry Chant. ( AAP: Joel Carrett )

She said any patients in intensive care units or who are suffering from pneumonia are being tested for COVID-19.

Dr Chant said people should seek immediate health assessment if symptoms develop after returning from at-risk countries including mainland China, Iran, Italy, South Korea, Japan, Singapore, Indonesia, Thailand, Hong Kong and Cambodia.

Australia has recorded 33 other cases of the virus, and one death on Sunday, but all other patients contracted the virus while overseas.

Peter Collignon, an infectious diseases physician at Canberra Hospital, said the person-to-person transmission was to be expected given the nature of the virus or any illness.

"I think it shows what you expect," Professor Collignon told ABC News.

"People who are in close proximity to those that are unwell may transmit this infection to others."

However, he said data shows even if one has close contact with an infected individual, this did not mean they would become infected as this type of transmission was low.

"If you look at the data coming from China, this is less infectious than I would have expected," Professor Collignon said.

"It appears that about 2 per cent of people that have had close contact [with an infected individual] may acquire the virus."