The rate of COVID-19 infection in Australia could be five times higher than reported, new research has found.
Research from the Australian National University and University of Melbourne show infection rates between March and August across 15 countries was on average 6.2 times more than reported cases, and up to 17 times higher in Italy at the height of the pandemic.
The study estimated the true number of infections across 800 million people in the United States, United Kingdom, Canada, South Korea, Australian and 10 European countries.
ANU co-author professor Quentin Grafton said the modelling found the infection rate in Australia was significantly higher than the confirmed proportion of 0.10 per cent of the population. More than 27,700 cases have been reported in Australia in total.
"Our modelling shows the actual rate of infected and recovered people at the end of August may have been five times higher than reported, with 0.48 per cent of the population, or up to 130,000 people possibly infected," he said.
"These findings raise serious questions about how we deal with all facets of the coronavirus pandemic, including ongoing morbidity and life-long health impacts for people who have been infected, how we implement and manage lockdowns, and how we make sure we are on top of this pandemic more broadly."
The true infection rate was determined by analysing the number of COVID-19 deaths in each country.
Researchers took the number of deaths in each country and worked backwards to calculate how many people would have been infected to arrive at that many deaths.
Professor Grafton said Australia had the best detection rate of the 15 countries in April of 50 per cent, but that dropped back to 20 per cent due to the Victorian outbreak.
"The key is people need to be encouraged to get tested and don't have disincentives to do the right thing," he said.
"We encountered that problem in Melbourne in June and July in terms of detection."
Professor Grafton said short wait times and financial assistance for COVID-19 patients or those waiting on results was critical to boosting Australia's detection rate back up.
As the Parafield cluster in Adelaide's north continues to grow, the state is being sent into lockdown for six days.
It's the "go hard and go early" response Professor Grafton said should be adopted given the new findings,and what was learnt from Victoria.
He said every day a community remained out of lockdown, as cases kept growing, could almost double the length of time strict rules would need to be in place to curb the spread of the virus.
"If you're getting 20 confirmed cases in Adelaide at the moment, the implication would be that you've got more than 20 cases, quite substantially more than 20 cases," Professor Grafton said.
"You might want to think maybe we've got 40 plus cases, or 50 cases potentially.
"Then you are in a different mode of thinking. It could be substantially more than we think so therefore we need to do something different."
Professor Grafton said it was unlikely Australia's detection rate could meet the true infection rate given the number of asymptomatic cases of coronavirus, but improvements could be made to return to 50 per cent.