The predicted summer Covid wave has hit Australia’s eastern states, with Queensland recommending the return of mask-wearing in some settings and new data showing a spike in cases and hospitalisations across New South Wales.
On Thursday, Queensland moved its Covid traffic light system to “amber”, recommending the return of masks among vulnerable people and in high-risk settings as the state entered its fourth wave.
It came as NSW recorded a 39.3% increase in Covid cases this week, alongside a spike in hospital and emergency presentations.
There were 14,089 recorded diagnoses of the virus in NSW in the week ending 5 November, as the PCR positivity rate jumped to 14%. Case numbers are likely higher than official figures suggest, however, as there is no longer any requirement to report positive rapid antigen test results.
NSW Health said the “substantial increase” in transmission was driven by a mix of new and emerging variants including BR.2, a sub-lineage of BA.2.75, XBB and BQ.1.
Hospital admissions had also begun to increase, jumping to 310, while emergency department presentations rose by 37 to 160 compared with the previous week.
Dr Norelle Sherry, a medical microbiologist at the Doherty Institute, was conducting genomic surveillance of Covid to gauge the level of case numbers in the community. She said it had become “a lot more unknown” with the easing of PCR testing.
“The waves coming through have changed compared to what happened with Omicron replacing Delta and BA.1 replacing BA.2,” she said.
“We’re now seeing lots of multiple lineages come out at similar times that have lots of the most successful mutations for immune evasion and transmission … contributing to an upswing.
“The Omicron sublineages are increasing like a Covid soup.”
Sherry said the good news was emerging variants appeared to have a lower disease severity compared to Delta, as was consistent with Omicron strains. But the bad news was they were highly transmissible, and better at evading immune systems – including for people who had previously been infected or vaccinated.
The chair in epidemiology at Deakin University, Catherine Bennett, said it was unlikely Australia would return to a period when just one variant of Covid-19 was circulating in the community.
“It’s a fundamental shift in epidemiology and it is a challenge,” she said.
“Rolling waves are going to push the infection risk up from time to time … but what’s reassuring is hospital rates and death rates didn’t show the same spike with transmission [of new subvariants] overseas.”
Bennett said moving forward she was hopeful the winter flu and Covid booster may be rolled into one vaccine, which could be distributed during challenging waves.
The University of Melbourne professor of epidemiology, Tony Blakely, said it was difficult to predict what the coming months would hold, however, it may be appropriate to take greater personal precautions as the wave peaked.
“We may be looking at a Christmas and New Year period, again, with high numbers of infection in the community, and some pressure on hospitals,” he said.
“This may appropriately see some reinstatement of mask rules to just take the edge off things and protect health services, and a push for people to get a booster shot.”
Blakely said as Covid continued to circulate in the community it was likely Australia would change their vaccination policy to become more “nuanced”, especially if a “new and concerning wave” was approaching.
Just over half of eligible Australians have had a third Covid vaccine dose, and just over 41% have had a fourth, according to the latest data.
Blakely predicted instead of recommending certain age groups have their “fourth” or “fifth” vaccine, the health department would instead pivot to making the public eligible for boosters based upon the time since a last dose or infection – such as four to six months for elderly people and vulnerable.
“Depending how serious the next ‘soup of variants’ wave will be, it would be astute for the elderly, immunocompromised and those with co-morbidities (at least) to keep up to date with vaccine doses,” he said.
A spokesperson for the Department of Health and Aged Care said Atagi had not made any recommendations for additional Covid doses beyond the severely immunocompromised and met frequently to assess the latest evidence.
The chief medical officer, Prof Paul Kelly, said evidence was still emerging but the experience overseas suggested new variants did “not appear to pose a greater risk” of severe illness and death.
“All indications are that this is the start of a new Covid-19 wave in Australia,” he said. “This was to be expected and will be part of living with Covid-19 into the future.”
Results from two complementary national serosurveys released this week found at least two-thirds of Australians, including children, have been infected with Covid-19.
The surveys, which test blood samples for antibodies to Covid-19, have been used during the pandemic to track Sars-CoV-2 infection across Australia to the end of August.