Australians can expect to be cooped up in isolation until summer, based on yet-to-be-released modelling that reveals the number of hospitalised coronavirus cases won't peak until the end of October, news.com.au reports.
The modelling, presented to intensive care consultants and seen by news.com.au, shows strict social distancing measures will halve the number of infections in NSW compared with what would have happened without the shutdown.
If not for the restrictions, the rate of transmission would have been much more aggressive and hospitalisations would have peaked in July.
The modelling shows that, with fewer government directives, there would have been a peak of 450 hospitalised cases for every 100,000 people in NSW, with the virus spreading in the community at a rate of 2.4.
With social distancing, the data shows the peak will now be late October, with 180 hospitalised cases per 100,000 people at a reproduction rate of 1.6.
The modelling shows social distancing measures are effective at flattening the curve and far fewer people will get infected, but also suggests Australia will be fighting the virus longer than expected.
Considering NSW has the highest case numbers, medical experts believe this projection will likely translate into the extension of nationwide restrictions until summer.
It has also created concern within the medical industry that intensive care units will be overwhelmed by seriously ill coronavirus patients.
Australian National University infectious diseases physician and microbiologist Professor Peter Collignon said he was sceptical of the validity of models that forecast infection rates.
But he told news.com.au the country would need to remain locked down, to some degree, well past Christmas despite the growth rate of new infections halving in recent weeks.
"You know what the bad news is? We're going to have to do a lot of this social distancing for another 18 months to two years," he said.
"This virus ain't going to go anywhere soon. We'll have a reprieve next spring because there's less transmission of viruses in summer.
"But until we get a vaccine that is safe and works or until we find the evidence is wrong or unless something radical changes with the data, there's no way, in my view, we're going to get rid of all the virus from Australia."
Collignon believes the tight lockdown in NSW and Victoria is unnecessary because there hasn't been evidence of widespread uncontrolled transmission.
Social distancing practices, which included closing pubs, clubs and other public gatherings, were enough to control the spread of the disease, he said.
This means measures that include keeping 2m and ending indoor gatherings will likely need to be enforced for up to two years.
"Most of the things we've done — that have put a million people out of work in Australia — we are going to have to continue to do," Collignon said.
Extended lockdown will cost $500b
The initial expectation was the coronavirus would stall trading for a short period, resulting in a major hit to Australia's gross domestic product in the second quarter, and then bounce back in the three months after.
But the extended lockdown expected by Collignon and the delayed peak of hospitalised patients will likely affect the nation's economy for two quarters.
Leading independent economist Saul Eslake told news.com.au this would lead to the already eye-watering cost of the pandemic blowing out exponentially.
He said the federal government had so far committed more than $200b in stimulus packages, state governments have coughed up close to $50b, and all have missed out on at least $100b in taxes because of the crippling disruption to business and trade.
Given almost all of the relief measures have a shelf life of six months, extending the support beyond two quarters would cost federal and state governments at least $500b, Eslake said.
"There could be pent-up demand [for some industries]," he said.
"But the holidays that aren't taken, the meals that aren't eaten, the visits to the cinema or the theatre that aren't done can't be replaced.
"So there are permanent losses."
AMP Capital chief economist Shane Oliver doubted the peak of the virus in Australia would be as late as November and expected the government to relax its shutdown in the coming months.
Such an elongation, he said, would result in "real damage" to the broader economy.
"The bottom line will feed into construction and manufacturing, whereas at the moment it's mainly service industries that are being heavily affected," he told news.com.au.
Oliver said a longer period for industries being crippled by the virus could lead to a loss to GDP of 20-25 per cent, which would be greater than the loss inflicted during the Great Depression.
"As you get further and further out, all the contractions that will occur will just start flatlining," he said.
•An exclusive by news.com.au