University of South Australia epidemiologist and biostatician Professor Adrian Esterman told parliament’s first COVID-19 Direction Accountability and Oversight committee hearing this morning that he was “completely convinced” that the state hit the peak of the current COVID-19 wave last week – likely on Thursday.

He said his calculations showed the state would hit the hospitalisation peak “in about a week’s time”.

However, chief public health officer Professor Nicola Spurrier said a short time ago that it “may be a little bit early to say that we’ve reached and we’re over the top of our peak”.

Esterman’s prediction is based on an “effective reproduction number”, which he said was determined by calculating the average number of cases over a series of days.

“If that number is getting bigger than one, the epidemic’s going up. If that’s equal to one, you’ve got that plateauing out – that trough. If it’s less than one, the epidemic dies out,” he said.

“What you see now is it’s gone below one.

“That tells me quite clearly that the peak has been reached and we’ve gone past the peak.”

Esterman said there would likely be a two-week time lag between South Australia reaching its caseload peak and for the hospital system to start admitting more COVID-positive patients.

“If we reached our peak of cases at about the 21st of July, then we should be hitting our peak hospitalisations in about a week’s time,” he said.

“There has been quite a steep increase in deaths over the last month, however, I do expect or hope it will go down when we see hospitalisations go down, so that will be in the next week or two.”

Spurrier, who recently left isolation after testing COVID-positive, said that while the number of active cases had dropped over recent days, it was too early to confirm whether the state had hit its caseload peak.

“We’ve got school going back this week and of course children will be mixing and we might see those infections then that transmission pick up,” she said.

“But, certainly we haven’t seen increasing numbers this week.”

It comes as South Australia today reported 3148 new COVID cases today – down from 3957 yesterday.

There are currently 341 COVID-positive patients in hospital, an increase from yesterday’s figure of 339.

SA Health today reported eight COVID-related deaths, including a woman in her 80s, two women in their 90s, four men in their 80s and one man in his 90s.

Those deaths occurred between February 23 and July 27.

Esterman said it was likely South Australia had “two or three times” more COVID cases which were going undetected in the community, but he said there was no way of determining the actual number.

“Wastewater analysis is showing high levels of fragments of the virus, especially in Bolivar, but in all these other areas as well,” he said.

“Importantly, if you look at the… PCR test positivity rate – which is basically if you’ve got 100 tests, how many of them turn out positive – at the moment it’s around 20 per cent.

“That’s a very high level.

“WHO (World Health Organisation) says if it’s five per cent or lower, things are under control, so clearly they’re not under control.”

Esterman said cases were likely going undetected in the community because about 40 per cent of infectious people have no COVID symptoms.

He said given it is the middle of winter, some people might dismiss COVID symptoms thinking they are “just a sore throat”.

“Then you get people who do test themselves because they’ve got some symptoms that comes out negative and unfortunately, the rapid antigen tests aren’t all that accurate,” he said.

“Quite often they’ll miss 40 per cent of positive people.”

Spurrier told the committee that the current COVID wave, spurred by the BA.4 and BA.5 Omicron subvariants, “was not going to be the last one”.

She said the BA.4 and BA.5 subvariants now account for about 80 per cent of cases in South Australia.

“Nobody has that crystal ball unfortunately to know what the pandemic is going to throw us next,” she said.

“But, I guess having had that experience already, the expectation is that we will have subsequent waves.”

Spurrier rules out mask mandate

Meanwhile, Esterman once again urged the government to impose a face mask mandate.

“How can we take the pressure off our hospitals? Well, if it was me in charge, I’d be introducing a face mask mandate for a start, but unfortunately it’s not me in charge,” he said.

“What we can do is much better messaging and I would be doing strong messages on television, radio and in the media.

“I’d be getting messaging about booster shots and why it’s so important, about face masks and about long COVID.”

Spurrier said SA Health had “sent out a lot of messaging” encouraging people to wear masks, including radio and digital advertising.

She said she also sent letters to businesses and universities urging them to recommend mask-wearing.

But, Spurrier said she did not recommend that the government impose a mask mandate.

“Masks are only one part of our risk mitigation strategy and to be successful in the pandemic, you have to have the community on board.” she said.

“That is the most important thing, really, is that confidence that the community has (to) understand that things that are being applied to them are proportionate to the situation.

“We all know that mask can help and it reduces the transmission potential by about 10 per cent, so it doesn’t do everything.

“But, the higher the rate of mask wearing the better for everybody.”

The COVID-19 Direction Accountability and Oversight Committee is chaired by Greens MLC Robert Simms and is tasked with inquiring into COVID directions and the state’s handling of the pandemic.