The United States has banned travel from Europe to the US, excluding Britain. On Thursday, Health Minister Greg Hunt asked the national health advisory committee whether Australia should follow suit. It is understood the group recommended against the move for now.

On Wednesday, Australia announced that travellers from Italy would not be allowed to enter Australia, with bans also in place for Iran, South Korea and China.

Mr Hunt said the health advisory group continued to advise that mass gatherings did not need to be cancelled.

Education Minister Dan Tehan said an extension of the Easter school holidays was being considered, but had not been recommended by the medical group at this stage.

While anxiety is increasingly gripping the nation, numbers continue to rise slowly in Australia, with 126 cases reported nationally by Thursday morning, but more also diagnosed. Movie star Tom Hanks and his wife Rita Wilson tested positive to coronavirus on Thursday while he was in Brisbane for filming and the couple are now reportedly in a Gold Coast hospital. The ACT reported its first case on Thursday, but the ACT government has released no details other than saying the person was a man in his 30s.

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Another person who attended a Universities Australia conference at the end of February in Canberra has tested positive.

NSW Chief Medical Officer Kerry Chant predicted that 20 per cent of the NSW population would be infected.

Victoria's Health Minister, Jenny Mikakos, said "extreme social distancing measures" would be needed at some point but not yet. Eight Formula One Grand Prix team members were being tested on Thursday in Melbourne. Italian-based team Ferrari received an exemption from travel restrictions to attend.

In Italy, numbers rose from 155 cases two and a half weeks ago, on February 23, comparable with Australia's case numbers now. But since then numbers have skyrocketed to almost 12,500 with 827 deaths and hospitals overwhelmed. In the same period, reported cases in Japan have jumped from 170 to 639, with 15 deaths.

The Grattan Institute says Australia must act quickly to avoid following the path of Italy and other countries, which had shown the "terrifying maths of exponential growth". Singapore and Hong Kong had avoided the Italian outcome through closing schools, universities, childcare centres and public gatherings, and other aggressive efforts. It had "not been pretty" and had come at a real economic cost to households and businesses, but appeared to have worked, Australia could follow suit, the group said.

Associate professor at the Australian National University medical school Sanjaya Senanayake said predictions varied wildly on how many people would eventually be infected, and "the honest answer is we don't know".

In Italy numbers grew much faster than in recent days in Australia, and the older population in Italy could partly explain the seriousness of the virus there. It was also possible that people who were more sick might be more infectious.

"We have to prepare for a worst case scenario and be ready for that but it may not eventuate," he said. "Only in hindsight will there have been a right or a better way of doing things. We have got local transmission and we have to keep an eye on it, but I'm hoping our health departments are on to it."

One of the questions was how the virus behaved over winter, with coronaviruses a having a preference for winter, potentially making things worse.

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