Two people in New South Wales have become the first in Australia to be infected with coronavirus through human-to-human contact.

A 53-year-old male doctor contracted COVID-19 after treating a female patient for the respiratory illness. He had not travelled in the last three months.

The second, unrelated case of human-to-human transmission is a woman whose brother had recently returned from Iran with the disease.

Disinfection professionals, wearing protective gear, spray antiseptic solution to guard against the coronavirus (COVID-19) at a department store on March 02, 2020 in Seoul, South Korea. (Getty)

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NSW Health Minister Brad Hazzard said while now is not time to panic, it may be a good idea "to cease handshaking".

"It may be a case of Aussies giving each other a pat on the back instead of a handshake," said Mr Hazzard.

The first case of COVID-19 has also been confirmed in Tasmania, bringing the total number to 31 in Australia.

This comes after airline passengers on a number of flights were warned to monitor themselves for symptoms after four Australians tested positive for coronavirus after returning from Iran.

In the latest NSW case, a Sydney-based woman aged in her 50s was hospitalised with the illness on Saturday almost a week after returning from Iran, NSW Health has confirmed.

The woman is believed to have been infectious during her flight, and those who travelled on the Qatar Airways flight QR908 from Qatar to Sydney scheduled to arrive at 6.45pm on February 23 are being urged to be on alert for symptoms of COVID-19.

There are 29 confirmed coronavirus cases in Australia as of 2nd March 2020. Graphic (Graphic: Tara Blancato)

She returned from Iran last Sunday before developing symptoms the following day.

However, she wasn't isolated until she attended an emergency department on Saturday.

Today Tasmania recorded its first coronavirus infection, also a traveller from Iran.

Earlier, health officials have updated their travel advice for Italy, South Korea, Japan and Mongolia, warning Australians to exercise a high level of caution.

Travel advice for Indonesia - which includes Aussie holiday favourite, Bali - has also been upgraded to the same level.

Meanwhile, the highest warning level of "do not travel" has now been rolled out to Iran, as well as centre of the outbreak, China.

This illustration provided by the Centers for Disease Control and Prevention (CDC) in January 2020 shows the 2019 Novel Coronavirus (2019-nCoV). (CDC via AP)

What is COVID-19?

COVID-19 is a specific type of coronavirus that causes severe lung disease and originated in China on December 31, 2019.

Coronaviruses are a large group of viruses that are common among animals and cause illness ranging from the common cold to more severe diseases such as Severe Acute Respiratory Syndrome (SARS).

The name comes from the Latin word "corona," meaning a halo or crown, which the viruses resemble when viewed under a microscope.

The current outbreak is most likely to have started from people who picked it up from a fresh food market, also known as a 'wet market', in Wuhan, China.