Until most public health restrictions were dropped in favour of reliance on vaccines for protection, Australia had one of the lowest death rates in the world, with only 2387 deaths across the pandemic up to the end of 2021.
Virologists are increasingly of the view that new, more transmissible omicron sub-variants, such as BA.4 and BA.5, will continue to evade infection immunity, meaning Australia enters winter in a vulnerable position with one of the highest per capita caseloads in the world.
BA.4 and BA.5 have led to a sharp rise in cases in South Africa, where lab tests suggest they are even more contagious than the highly infectious BA.2 and BA.1 variants.
The boost in transmissibility was “quite an advantage”, Belgium evolutionary biologist Professor Tom Wenseleers told Nature journal.
“Taking everything together and looking at all the data, it seems a sizeable new infection wave is certain to come.”
However, virologists are optimistic that the continued evolution of omicron could be another sign the pandemic is changing character, with waves coming from current strains rather than whole new variants seemingly unrelated to each other.
“These are the first signs that the virus is evolving differently,” South African bioinformatician Tulio de Oliveira told Nature, compared with the first two years of the pandemic when variants seemed to appear out of nowhere,
Virologists are hoping this means the evolution is beginning to resemble influenza, with omicron exploiting falls in population immunity and driving a roller coaster of periodic waves, rather than sharp spikes.
“It is probably what we should expect to see more and more of in the future,” South African virologist Penny Moore said.
The first strains of BA.4 were reported in Australia in late April as the country battled an already large omicron caseload.
According to data from Johns Hopkins University in the US, Australia’s current seven-day average case rate per million is 1632. This compares with 646 cases per million in Singapore and 227 cases per million in Japan. Australia’s per capita caseload is 10 times that of the UK and more than seven times the US.
With all major public health restrictions now relaxed, Australia is heavily reliant on waning vaccine immunity to defend against widespread acute sickness and death.
There are variations across the country, but at a national level all the major indicators of cases, hospitalisations, ICU admissions and deaths are slowly but steadily increasing, according to data analyst Mike Honey.
“All the indicators for Australia are trending up,” Mr Honey said.
These are being fuelled by the BA.2 autumn wave, which, while not reaching the peaks of the BA.1 summer wave, is remaining particularly stubborn.
As temperatures began to fall, Victoria recorded 12,722 cases on Tuesday, its highest number of cases in over three months. Western Australia recorded its highest level of cases in the pandemic, with 12,390 cases.
Nationally, one in five PCR tests is testing positive, suggesting high undetected prevalence rates as case numbers edge back up to levels similar to late January.
The seven-day average now sits at around 42,000 cases a day, with more than 2.6 million people, or 10 per cent of the population, having reported getting COVID-19 in the autumn period alone.
The lift in cases is beginning to again be seen in deaths, with the seven-day average for deaths back up at 35.6 this week, compared with 20.6 in mid-March.
