Australians returning from Italy or South Korea, who are employed in the medical and aged care sectors, are being told not to return to work for a fortnight.

Key points: Outbreaks of coronavirus in Italy and South Korea prompted the Federal Government to expand quarantine advice

Outbreaks of coronavirus in Italy and South Korea prompted the Federal Government to expand quarantine advice Australians in both countries are being told to exercise "a high degree of caution"

Australians in both countries are being told to exercise "a high degree of caution" However, the Government has opted against extending its travel ban to both countries

The Health Minister Greg Hunt says the country's chief medical officers have recommended the extra precaution for certain professions.

Australians are being told to "exercise a high degree of caution" in Italy and South Korea.

"We do believe that there are some people whose symptoms are so mild that they may be almost unaware that they are infected, particularly just as they become infectious," chief medical officer Brendan Murphy said.

"That is one of the reasons why quarantine is still being practised for very, very high-risk situations.

"But, all of the evidence suggests people are most infectious when they are symptomatic. That is still the most important piece of advice, to isolate when you are symptomatic."

The number of coronavirus cases in Italy rose 50 per cent in just 24 hours, local authorities have announced overnight.

Meanwhile, the leader of a religious sect in South Korea is facing charges of gross negligence over some of the country's coronavirus deaths.

The Federal Government has had a ban on foreign nationals travelling from China to Australia for the past month.

Mr Hunt extended that ban to include Iran on Saturday.

So far, Australia has recorded 29 cases of the coronavirus, of which four travelled from Iran.

"We had a very high suspicion that the caseload in Iran was much greater than being reported because of the death rate," he said.

"So even though we have a relatively low travel volume from Iran, we have had these four cases so that's why Iran has been a particularly special case."

A foreign national travelling from China or Iran must spend 14 days in a third country before being allowed into Australia under the ban.

But the Government has opted against extending that to people travelling from South Korea and Italy.

"At the moment, the medical advice was that the situation in Italy and South Korea, where they have large outbreaks but they are confined and been localised, the proportionality of putting in a travel ban wasn't justified in terms of its benefits of health protection of the Australian community," Dr Murphy said.