The remarks confirm the long timeframe for business closures and curbs on social activity amid fears of a mounting economic cost, as Mr Morrison urged Australians to keep to the strict controls this Easter weekend.
While the modellers chose not to estimate the deaths that might have occurred without intervention such as travel bans and business closures, they found only 30 per cent of patients would have gained a hospital bed in an uncontrolled pandemic.
The government said its current approach lifted that ratio to 100 per cent.
Doherty Institute epidemiologist and University of Melbourne professor Jodie McVernon, one of the government’s top expert advisers, cautioned against claims any single measure – such as school closures – could slow the spread of infection.
“We need to keep watching, we need to keep looking, we need to keep learning,” she said.
Mr Morrison outlined the long-awaited modelling with an emphasis on the need for a six-month timeframe for the health and economic measures, compared to the three-month plans in place in other countries.
“We have bought valuable time but we cannot be complacent,” he said. “We must keep the tension in the cord.”
Chief Medical Officer Brendan Murphy said the country would have faced a “horrendous scenario” without the travel bans and other measures because the pandemic would have required daily demand from more than 35,000 patients for new intensive care beds.
In a teleconference to outline their findings, Professor McVernon and Professor McCaw said more work would be done over the next two weeks to calculate the impact of measures taken so far to keep infections down.
“We agree that given the control measures we have in place at the moment, we can see in the data that it looks like the curve is flattening and flattening strongly,” said Professor McCaw, a professor of mathematical biology.
“If we can maintain the level of the interventions that we have today ongoing, you would expect to see a further decline in cases.
“There’s fewer importations from returning travellers or returning Australians and it looks like community transmission is continuing to be well-suppressed.
“So in that sense you would say that it looks from a case infection point of view that a peak might have almost passed, or is passing, and then we will see a surge in hospitalisations in the coming week and then that would die away.
“But then of course we know that our population is still largely susceptible, so if we relaxed and went back to normal we would see a rapid, explosive resurgence in epidemic activity.”
The warning highlights the tension within and between governments over the timetable to ease the restrictions on economic activity, as Parliament meets on Wednesday to vote on the $130 billion JobKeeper package to support six million jobs for six months.
The new scientific papers were published by the Peter Doherty Institute for Infection and Immunity on Tuesday and supported the government modelling, but the document released by the government did not contain forecasts based on Australian data.
The government acknowledged more work would be done over the next two weeks on the Australian figures to decide whether further restrictions would be required or whether existing measures were adequate.
Professor McCaw said Australia had reached a “critically important state” where the community was suppressing the infection and keeping our hospital system under control but could not maintain its strict controls forever.
That meant the risk would remain because the epidemic would spread around the world even if Australia brought it under control.
“It’s almost implausible to imagine this virus going extinct globally, which means that it will be here to stay,” he said.
“It will become a part of our everyday life and the transition to it not being a huge driver of complete societal change is a very difficult thing to work through.”
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David Crowe is chief political correspondent for The Sydney Morning Herald and The Age.
Eryk Bagshaw is an economics correspondent for The Sydney Morning Herald and The Age, based at Parliament House in Canberra