Victoria was seemingly blindsided by an explosion of coronavirus cases ahead of Melbourne's stage 4 lockdown and new figures may reveal why.
Economist and modeller Professor Quentin Grafton of Australian National University told news.com.au that an estimated 30 to 60 per cent of the state's coronavirus cases in June and July were in fact cases of hidden community transmission.
"Our model shows that this was a significant generator of the outbreak in Victoria," he said.
"It shows the real problem – that if people don't want to get tested, authorities won't know what's going on. (In this scenario) contact tracing doesn't work."
The problem is a warning for NSW, which is facing calls to introduce paid pandemic leave as it struggles to contain its own outbreak.
The possibility of hidden community transmission means for every positive case there could be many more cases that aren't identified.
"Positive cases are always underestimated," Prof Grafton said.
On Wednesday, Victorian Premier Daniel Andrews warned that the state's lockdown was at risk of being extended because of the dwindling number of people being tested. Some testing centres are seeing as few as 20 people a day.
Andrews said authorities needed testing to go up so they could get a "complete picture" before easing stage 4 restrictions.
"What we're all trying to avoid here is that cases come down to a point where we start to think about opening up ... only to be unable to do that because the test numbers are too low for us to have clarity about just how much virus is out there," he said.
The Royal Australian College of General Practitioners has suggested some Victorians may not want to get tested because they want to avoid the stigma of being found positive.
"We are dealing with a disease that engenders a great deal of fear and anxiety," board member and Melbourne GP Lara Roeske told The Age.
Another Melbourne doctor told the newspaper one of her patients was kicked out of her share house and vilified by friends on social media after she returned a positive test.
Wednesday marked the day that Melbourne's original stage 3 lockdown was supposed to end, but daily new case numbers were higher now than when it began.
On July 8, the state recorded 191 new cases, six weeks later Victoria's new cases were higher – at 216 cases – despite the lockdown
'It's a very dangerous thing'
Grafton said Victoria's first cases in hotel quarantine were infected in late-May but it wasn't until mid-June that authorities identified an outbreak. It took more than three weeks for Victorian authorities to act, announcing a reversal of the relaxation of restrictions on June 20.
It's now believed the virus was spreading for quite some time without being noticed by authorities, partly because many people were not getting tested.
"By the time authorities got into gear, the outbreak was already underway and it was bigger than they thought," he said.
Grafton said there was a delay because authorities didn't understand the extent of the problem.
"Eventually we got to stage 4 but this was quite some time after the initial outbreak," he said.
"This is why hidden transmission is so deadly, it's just a very dangerous thing."
There may be many reasons why people were not getting tested but one factor was likely due to their employment.
"For those in casual work, if they don't work then they've got no earnings," Grafton said. "If you stand to lose four or five days pay you might not get tested if you've just got the sniffles. So the incentive was to not get tested."
This allowed the virus to circulate for quite some time before enough people got tested and authorities were alerted to an outbreak.
"This is something they should have planned for but they didn't," Grafton said.
NSW also at risk
Grafton said Victoria's example pointed to why NSW could not afford to be complacent, despite its apparent success in bringing down its case numbers without a lockdown or mandatory masks.
On Tuesday, NSW recorded just three cases after regularly recording around 20 cases a day once the Crossroads Hotel outbreak was discovered.
However, NSW Health warned of hidden cases. "Even though daily case numbers are low, there have been 16 cases in the last four weeks whose source is not identified or linked to clusters, mainly in western and south-western Sydney, indicating that Covid-19 is continuing to circulate in the community, undetected," a statement said.
Grafton said NSW also had a large casualised workforce in Sydney that posed the same risk as what was present in Victoria.
"Victoria was thought to have one of the best testing and tracing systems but it was not enough," he said.
"I think NSW has learnt from that, it's doing an effective job testing and tracing but I hope it's enough."
NSW may already be facing a challenge after a Sydney security guard at the Marriott hotel in Circular Quay tested positive this week. The guard also worked at Parramatta Court, Flemington market and Bankstown Central Shopping Centre.
Australian Council of Trade Unions secretary Sally McManus said labour-hire and insecure work had already spread the virus in Melbourne and the same thing was now happening in Sydney.
"People in high-risk workplaces such as hotel quarantine should not have so few hours and no sick leave," McManus told The New Daily.
"This leads them to working across multiple workplaces when sick out of economic necessity, spreading the virus far and wide."
NSW is now facing increasing calls to introduce paid pandemic leave.
The Victoria and Commonwealth governments introduced a $1500 disaster payment for those without sick leave who have to self isolate, to encourage people to get tested.
However, these payments are not available in NSW.
McManus said on Sunday the NSW government needed to ensure all workers had access to sick leave during the pandemic.
"NSW has to learn from the second wave in Victoria and provide paid pandemic leave now, so all workers can take time off to get tested or isolate, keep themselves safe and protect the community," she said.
"Workplace transmission caused by insecure work forcing people to work while sick has led to hundreds of cases in Victoria; now is the time to act to prevent this in NSW."
News.com.au has contacted the NSW government for comment but has not received a response.
The argument for zero cases
The presence of hidden transmission is why Prof Grafton believes it is better to get to zero cases before relaxing restrictions in Victoria.
"If we get to no community transmission then less social distancing will be required over the next 12 months than if there was still some level of community transmission," he said.
"We are actually better off taking that extra couple of weeks to get to no community transmission."