Updated April 07, 2020 23:31:57

Photo: All the modelled scenarios result either bad health outcomes or "extensive long-term lockdowns", one epidemiologist says. (ABC News: Brendan Esposito)

The experts behind some of the modelling used to determine Australia's coronavirus response say Australia is in a "lucky" position — but the fight against COVID-19 will continue as the virus is "here to stay".

Melbourne's Doherty Institute, which has been critical in the Government's coronavirus decision-making process, on Tuesday released its early-stage modelling which helped inform the Morrison Government's early measures in the fight against the disease.

Doherty Institute and University of Melbourne infectious diseases epidemiologist James McCaw — who was involved in the modelling — said as the Government had acted early, it could now make considered decisions.

He said they put some "very scary numbers" to the Government early on, and they were not dismissed.

"[Now] we're in a very lucky position where we can think about the next steps and the very challenging questions ahead from a position of relative calm as opposed to crisis," he said.

"We don't have an overwhelmed hospital system yet and we may well never have one if we continue to base our responses on the best available data."

Photo: Experts say physical-distancing measures have helped Australia 'flatten the curve' (ABC News: Brendan Esposito)

The Doherty Institute report released on Tuesday modelled a "worst-case scenario" of the impact of COVID-19 in Australia to inform transmission-reducing measures and health system preparedness. It also released a separate report which assessed the impact of returned travellers.

One scenario looked at what would happen if 23 million Australians became infected with COVID-19. It found that would have resulted in more than 35,000 intensive care beds being needed each day.

The other scenarios looked at the impact of quarantine, isolating people with the virus and social distancing.

If all the measures were introduced, researchers found, there would be a 33 per cent reduction in transmission, with only 12 per cent of the population infected.

That would mean only 5 per cent of people would require medical care, so "everyone who needs an ICU bed could get one".

Those measures have been put in place.

Breaking down the latest news and research to understand how the world is living through an epidemic, this is the ABC's Coronacast podcast.

Prime Minister Scott Morrison and Chief Medical Officer Brendan Murphy held a joint press conference on Tuesday on the issue.

They said the modelling using data from Australia's almost 6,000 people infected with the disease — and the next steps in fighting it — would not yet be released.

Professor Murphy said the current data — and Australia's next response — was "still confounded by returned travellers" and would not be clear for "weeks".

"It's currently in the hands of our modellers," Professor Murphy said. "Once we have something valid and useful [it will] be released."

However Professor Murphy said Australia was "on a life raft and we have the opportunity to decide our course".

"The data we have so far suggests [what we're doing] is working," he said. "We are flattening the curve. But complacency is our biggest risk."

Modelling explained

Modelling assesses both macro and micro responses to the pandemic.

A macro-level assessment is where the entire population is modelled at once to estimate the average rate of spread of the virus. The second is on a more detailed, micro level, where every person in Australia is represented and accounted for.

The micro-simulation modelling is the type the Government's team is currently doing, with a range of parameters and scenarios explored.

Professor McCaw used the analogy of a weather forecast. He said the macro analysis was like a long-term climate change forecast, whereas the micro analysis was a day-to-day short-term forecast.

Photo: Epidemiologist James McCaw says it appears the peak is either passing or has passed. (University of Melbourne)

He said Australia would see an increase in hospitalisations, admission to ICU and deaths from Tuesday's levels, with that wave driven by the past cases from the last few weeks.

He said the curve in the rate of new infections was flattening, but the next few weeks were "absolutely critical".

"It looks like the peak might have almost passed or is passing," he said.

Doherty Institute professor and director of epidemiology Jodie McVernon said "we're in a very stable position".

"We've been able to see the experience of other countries and adapt," she said.

However some experts were more circumspect.

James Trauer, an epidemiologist at Monash University, said all the scenarios were "pretty depressing", resulting in either bad health outcomes or "extensive long-term lockdowns".

"We need to make some decisions soon and be clear on what they are and base our public health decisions around that," he said.

Virus 'here to stay'

Professor McCaw said how to move forward in the long term was an issue the world needed to grapple with.

"Even if we eradicate the disease in any given country such as Australia, we know that there is an epidemic spreading around the world," he said.

"It's almost implausible to imagine this virus going extinct globally, which means that it will be here to stay.

"The real question is how do we transition to a world where the virus is part of everyday life."

Topics: health, epidemics-and-pandemics, diseases-and-disorders, health-policy, health-administration, environmental-health, lifestyle-and-leisure, australia

First posted April 07, 2020 19:34:27