Australia potentially faces widespread Covid-19 infections doctors say, warning that chronically overstretched public health systems could be overwhelmed in the event of a severe pandemic.

Up to 70% of Australians could be infected in the event of a severe pandemic, though governments and health professionals have stressed that most healthy people will only experience the illness as a mild to moderate cold.

Globally, there have been more than 83,000 confirmed cases of coronavirus, leading to more than 2,800 deaths. The vast majority of infections and deaths have been in mainland China, though fast-spreading outbreaks have emerged in Iran, South Korea, and northern Italy.

Government plans contemplate successive waves of pandemic reaching Australia and spreading throughout the community. Quarantine, self-isolation and social distancing measures could be encouraged or enforced in order to slow the spread of the virus through the community.

Prof Raina MacIntyre, head of the biosecurity program at the Kirby Institute at the University of New South Wales, said sustained transmission may result in anywhere from a quarter to 70% of the Australian population being infected.

Covid-19 – the disease caused by the Sars-CoV-2 virus – has a case fatality rate of between 2-3%.

“To put it in context, the case fatality rate of the 1918 flu pandemic was 5%, and the 2009 pandemic, 0.01%,” said MacIntyre.

“So, a case fatality rate of 2-3% is high. In China, we know that in addition to the people who died, 5% needed to be in ICU and 14% needed a hospital bed.”

MacIntyre said Australia had done an excellent job, so far, of preventing sustained transmission in the country, but that the country was now moving to the next phase of response: managing a pandemic outbreak.

“If 50% of Australians – 13 million people – became infected that is up to 400,000 people dying, almost 2 million people needing a hospital bed and 650,000 people needing an ICU bed.

“These are total numbers over the whole epidemic, which may last one year.”

Australia’s chief medical officer, Dr Brendan Murphy, said Australia was well-prepared for the potential outbreak of Covid-19 in the wider community.

“We have accepted the very strong likelihood we will get further cases and some further transmission of this virus in Australia,” he said.

“We are still contained in Australia. We do not have any evidence whatsoever of community transmission in this country. Whilst we are preparing and we are realistic about what might come in future weeks. We are not in a situation where anyone needs to be concerned.”

Murphy said more than 80% of Covid-19 patients had a “very mild illness” and in Australia, now “nobody should go around wearing and wasting face masks”.

Australia has stockpiled 20m face masks in the event of widespread a outbreak.

“We are not wanting the community to panic, but we are obviously being transparent in that we think the situation does mean it is very likely we will get some more cases in Australia in coming weeks,” Murphy said.

Raina said in Sydney, there were an estimated 16,000 public hospital beds, and 6,000 private beds.

“We have previously modelled the number of daily beds required in an epidemic scenario for a different infection, which shows that capacity for beds could be rapidly exhausted in a severe epidemic.”

Part of the pandemic plan “activated” by the Morrison government on Thursday – of which some elements were already in operation – involved preparing “surge capacity” in hospitals, including dedicated fever clinics, for the possibility of a high number of cases presenting.

This was met by warnings from doctors that hospitals – and medical staff within them – were already operating at capacity, and there was no room for any additional surge.

“Part of the pandemic plan is ‘hospitals opening their surge capacity’. Now, I don’t want to alarm anyone, but there is no surge capacity. It’s all open ... we are full everyday. We’ve been saying this for years,” past president of the Australasian College for Emergency Medicine, Dr Simon Judkins said.

“That capacity will be created through other means [cancelled surgery/outpatients] But, there are no excess beds or staff. If there were, our EDs wouldn’t be bursting, our ambulances ramping, and our staff burning out.

“Australia’s health system will manage this well, due to the hard work of healthcare workers. My point is that we operate our system at or over capacity and to pretend there is ‘surge capacity’ is wrong.”

The Australian government’s plan – the health sector emergency response plan for Covid-19 – involves an escalating series of responses, from self-isolation of suspected cases, enforced quarantining of known infectious patients, up to the closure of schools, cessation of public transport and advice – even orders – for people to work from home.

Under complementary state government pandemic plans: sports stadia may be sequestered as quarantine sites, police could be ordered to guard critical medical supplies, and governments may order entire suburbs, cities or groups of people to undergo mass vaccinations (once a vaccine is developed).

Prof Nigel McMillan, director in infectious diseases and immunology at Menzies Health Institute Queensland, Griffith University said many pandemic models of the disease’s spread were inaccurate because “we don’t know two important things: how many people get infected [infection attack rate], and how many get sick [clinical attack rate]”.

“That is, we suspect there are a large number of people who aren’t identified as having Covid-19 because they have a mild cold. We can make guesses, but it will take time to get this information.”

McMillan said a vaccine was likely 18 months away and would be useful only after the virus had gone pandemic.

“It will eventually become just another cold/flu type virus we have to deal with and that mostly kills old and very young people.”

He said media reports sensationalising the impacts of the virus would become problematic if a pandemic occurred, which now appeared likely as the disease spread in several countries.

“We don’t wish to induce panic food or petrol stockpiling etc when for 95% of the population, this will be a mild cold.

“Travel bans will no longer be useful or make sense and so health authorities need to prepare for the next phase. This includes preparing our hospitals for a large influx of patients, stockpiling any antivirals [some appear to work to slow the virus], and advising the public that when the time comes they will need to think about things like staying at home if ill, social distancing, and avoiding large gatherings.”

Virologist Ian Mackay, associate professor at the University of Queensland, said it was unrealistic to expec­t that the virus could be containe­d to certain regions, and all countries should prepare for managing an influx of cases.

“If the virus can’t be put back in its box worldwide, then it has the tools to become an endemic human coronavirus [we already live with four of those – HCoV-229E, -OC43, -NL63, and -HKU1]. Not today. Not tomorrow. Sometime in the future.”

“So it’s really important that we find, test and isolate the ill to slow the spread and give hospitals plenty of time to prepare and manage cases without being overwhelmed. Many countries probably can’t trace, test and isolate as well as China, Singapore, Hong Kong have.”