South Australia has confirmed its first two cases of coronavirus and Victoria its fourth, bringing the national total to 12.

Key points: The latest cases in Victoria and South Australia take the national total to 12

The latest cases in Victoria and South Australia take the national total to 12 There are no public exposure sites and no-one has been identified as having close contact with the woman

There are no public exposure sites and no-one has been identified as having close contact with the woman Monash University has announced it will delay classes on campus as some staff and students will not be back in time

Saturday's three new cases came as Prime Minister Scott Morrison announced DFAT had raised its travel advice for China to its highest level, urging Australians not to travel to the country.

Australia has also imposed strict restrictions on people coming from China, with exceptions given to Australian citizens, residents and their immediate family.

The couple in South Australia, a man and a woman both aged 60, were from Wuhan and visiting relatives in the state.

South Australia's chief public health officer Nicola Spurrier said they believed no one else in the state had been exposed to the pair.

"All of the right procedures were undertaken so we're not concerned about spread during that time and they have self-isolated in their home awaiting the results of the test," Dr Spurrier said.

"I can reassure people that we do not think there has been any contact with anybody else in the state," she said.

They have been placed in isolation in a public hospital.

Dr Spurrier said 25 people in SA had been tested for coronavirus and earlier on Saturday 15 of those tests returned negative results.

The case in Victoria, a woman in her 20s, is a resident of Melbourne and is recovering at home.

She returned from Wuhan, Hubei Provence, on January 25 and became unwell two days later.

She was seen by doctors in a Melbourne hospital on January 30 in accordance with infection control procedures and was assessed as well enough to stay at home.

Health authorities say she was not considered infectious on the flight and she has remained isolated since being tested.

There are no public exposure sites and no-one has been identified as having close contact with the woman.

NT investigates possible first case

Northern Territory health authorities are investigating a potential case of the virus.

Chief health officer Hugh Heggie said test results were expected back from Victorian laboratories on Saturday evening.

The potential case involved a person who arrived on a flight from southern China on Wednesday and was in isolation at home.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 49 seconds 1 m 49 s Scott Morrison announces a series of measures to clamp down on the spread of the novel coronavirus.

Dr Heggie said if the test returned a positive result, the NT had the capability to manage it and urged people to be vigilant.

"If people are unwell, they should contact the national coronavirus telephone line," he said.

"If their symptoms are increasing, they should contact the emergency department."

Dr Heggie reminded Territorians the case was yet to be confirmed, and as soon as test results returned, they would be released.

Northern Territory Minister for Health Natasha Fyles echoed the call for Territorians to be "alert, but not alarmed".

"So what we have here is we have people who have had connection, possibly to this virus, and they have presented with symptoms.

"We do not have confirmation of a coronavirus case."

Ms Fyles was not able to confirm if Australian patients en route from China to Christmas Island would stop in Darwin.

Government advises China travellers self-isolate

Foreign Affairs Minister Marise Payne said last week that more than 600 Australians had registered as being in Hubei province, of which Wuhan is the capital.

Millions of people in Hubei have been locked down as the Chinese Government fights to contain the spread of the virus.

Australians in Hubei will be flown to Christmas Island for quarantine.

The Centre for Disease Control and the WHO said there had been reports of the virus spreading from an infected patient with no symptoms to others in close contact, but more information was needed to confirm asymptomatic transmission.

Anyone who has travelled in China's Hubei province should self-isolate for 14 days after leaving, other than when seeking medical care.

Given the lower number of cases in China reported outside of Hubei province, the Victorian Government is recommending people who have recently travelled in other parts of China or other countries do not have to self-isolate at this time.

Queensland Premier wants all flights from China halted

Queensland Premier Annastacia Palaszczuk says she wants all flights to Australia from China to be halted until the coronavirus epidemic is contained.

A Melbourne woman infected with coronavirus has taken the national total to 10. ( AP: Mark Schiefelbein )

"I don't often agree with Donald Trump, but I do agree with the US authorities on this occasion that I think we should take every measure possible to combat this virus," Ms Palaszczuk said.

She said she wanted "further data" from the Federal Government about people flying into Queensland from China.

"We would like to know where they are so we can actually make sure they are getting the messages and they are self-isolating. I think that is really, really important and I think that's not just a state issue, I think that's a national issue," she said.

What to do if you are worried

The Victorian Department of Health and Human Services has established a coronavirus hotline on 1800 675 398.

Anyone who develops symptoms of fever and breathing difficulty or cough or who have had direct contact with a confirmed case should seek medical help immediately.

Before visiting a GP or emergency department, they are advised to call ahead to advise about recent travel and symptoms.