As the number of people dying from coronavirus rockets well ahead of those killed by SARS, experts say the disease's spread is now at a critical stage.

Key points: Coronavirus experts said there were still many unknowns, with China "swamped" with coronavirus cases

Coronavirus experts said there were still many unknowns, with China "swamped" with coronavirus cases The virus is understood to be more contagious than SARS, with about 20-25 per cent of cases considered "severe"

The virus is understood to be more contagious than SARS, with about 20-25 per cent of cases considered "severe" Experts believe the true test of the virus's spread will come when the travel bans out of China are lifted

Nine weeks after the novel coronavirus was first discovered, Australian infectious disease experts are only beginning to understand its severity, how it is spread and how to contain it.

In Australia, there are only 15 confirmed cases. Health Minister Greg Hunt says five people have recovered from the illness, while the remaining 10 are stable and in a "recovery process".

So the question remains: with thousands of Australians dying every year from influenza, and no coronavirus deaths reported in Australia, why are we still so worried about it?

According to leading virologist Ian Mackay, from the University of Queensland, the fact China has been "swamped" with cases means there are still many unknowns about the disease.

"[At the moment] the Chinese authorities can't even rely on the numbers being calculated in China," Dr Mackay said. "Their hospitals have been inundated.

"And without really good numbers and data we can't be sure [of anything]."

A worker sets up beds at a stadium to convert it into a makeshift hospital in Wuhan, China. ( Reuters: China Daily )

Dr Mackay said his concerns — and the reasons he believed the world was heading towards a pandemic — centred on the lack of immunity in the community, the spread of the virus, and the eventual lifting of the China travel bans, which the Federal Government says will be "reviewed" at the end of the week.

"Things like stopping flights out of China, these are things that I never thought I'd see in my lifetime," he said.

"And the travel ban has worked. But it can't go on forever.

"We all have very little immunity with coronavirus, which means it will run through a population. The virus has all the tools to spread wildly."

Dr Mackay's concerns are shared by Australian National University infectious diseases physician Sanjaya Senanayake.

He said although there were still many unknowns, the novel coronavirus appeared to be more infectious than SARS — in just nine weeks, coronavirus has eclipsed the number of SARS cases that took eight months to develop.

"When it comes to how fast coronavirus can spread between people, it looks like coronavirus can take about six to seven days," Dr Senanyake said.

"That's slightly longer than the flu, which can spread between people in four days."

However, chief medical officer Brendan Murphy has moved to reassure Australians that there has been "no community transmission" of the virus locally.

"There is no reason for people to be wearing masks," he said.

"There's no reason for people to avoid anybody of any particular background or appearance."

How is it different to the flu?

Dr Senanayake said many people diagnosed with the coronavirus would feel like they had influenza.

"Some people are getting a mild illness and it really varies, the symptoms will vary," he said.

"Nearly everyone gets a fever. Lots of people but not all get a cough, runny nose, muscle aches and pains.

"Interestingly, a variable number of people get diarrhoea, which is of interest to me because it looks like this coronavirus has some of the same receptors as SARS, which target cells not only in the lungs but the gastrointestinal tract.

"SARS spread through faecal matter. We don't know if coronavirus can spread this way as well.

"But in the US, they did isolate it [coronavirus] in poo. Odds on it is most likely it could [spread this way]."

In Australia, patients would be isolated in a single room and with their own toilet, which would not be the case in China where hospitals and medical professionals had been swamped.

Dr Mackay said his understanding was about 20-25 per cent of coronavirus cases in China were considered severe.

He said in the hundreds of cases outside China, the severity was "mild to very mild", and there were more resources put into treating the affected patients.

Immunity and our ability to fight off infection is considered another major difference between the flu and coronavirus.

Most people have developed some sort of immunity to the flu. But so far, that is not the case with coronavirus.

Professor Tania Sorrell, from the University of Sydney's Marie Bashir Institute for Infectious Diseases and Biosecurity, said coronavirus appeared to be a winter virus.

"It is still too early to predict what will happen with this illness [after the Chinese winter]," she said.

"But we may find that as it goes on, and if it goes on for a long period, some immunity will develop in the community."

What's next?

Dr Senanayake said health experts needed to know more about the cases in China to make any confident predictions.

"We need that data to know what's going on," he said.

"Because it is so new and none of us have immunity to it, if it did go around the world it would cause a lot of mild infections in people, which means people miss work and kids get sick.

"Even if only a small percentage get sick and need to go to hospital, that will put a strain on the health system.

"We are always worried that any new virus could be the next pandemic, the next 1918 — the flu that killed 40 to 50 million people."

Dr Mackay said the disease was set to stay in China "for a long time".

"My prediction is it will stay in China, and continue to seed the world until probably it becomes a standard virus like one of the many ones we see today."