Highly infectious COVID-19 variant XBB.1.5 is a reminder to maintain safety measures

Relaxed rules around face masks, air filtration and infection reporting will leave Australians vulnerable to the new variant, University of Adelaide Associate Professor Emma Miller told ACM.

"This sub-variant goes to show what can happen anywhere basic principles of public health management have essentially been abandoned," she said.

In a desire to return to normal, Associate Professor Miller said we had unravelled the infrastructure needed "to have an effective response to this virus".

"We're all over it and don't want to go back to restrictions," she said.

But abandoning previous strict surveillance and reporting measures from 2020-2021 would "make it really difficult to negotiate the public health aspects of this virus".

The World Health Organisation's senior epidemiologist Maria Van Kerkhove said XBB.1.5 was the most transmissible Omicron sub-variant detected so far. It spreads rapidly because of the mutations it contains, allowing it to adhere to cells and replicate easily.

XBB and XBB.1.5 were estimated to account for 44.1 per cent of COVID-19 cases in the US in the week of December 31, up from 25.9 per cent in the previous week, according to data from the US Centers for Disease Control and Prevention.

It has also been detected in 28 other countries worldwide, including Australia.

XBB.1.5 is yet another descendant of Omicron, the most contagious variant of the virus causing COVID-19 that is now globally dominant. It is an offshoot of XBB, first detected in October, which is itself a recombinant of two other Omicron sub-variants.

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The WHO said it does not have any data on severity yet, or a clinical picture of its impact. It said that it saw no indication that its severity had changed but that increased transmissibility was always a concern.

"We do expect further waves of infection around the world but that doesn't have to translate into further waves of death because our countermeasures continue to work," Van Kerkhove said, referring to vaccines and treatments.

She said the WHO was unable to attribute the increase in hospitalisations in the northeastern US to the variant, given that many other respiratory viruses were also in circulation.

Virologists agree the emergence of the new subvariant does not mean there is a new crisis in the pandemic. New variants are to be expected as the virus continues to spread.

XBB.1.5 is likely to spread globally, but it remains unclear if it will cause its own wave of infections around the world. Current vaccines continue to protect against severe symptoms, hospitalisation and death, the experts say.

"There is no reason to think that XBB.1.5 is of any more concern than other variants that come and go in the ever-changing landscape of COVID-19 mutants," Oxford Vaccine Group director Professor Andrew Pollard said.

The problem lies in public health policy Associate Professor Miller said, with Australia not surveilling cases of infection adequately.

"Our canary in the coalmine is gone when we don't surveil or require notifications of COVID-19," she said.

Current public health policy no longer requires mandatory isolation and infection reporting, leaving COVID-19 to move untraced through the community.

The first sign things are going pear-shaped will be when our hospitals become "jam-packed and our morgues start filling," Associate Professor Miller said.

"That should send shudders," she said.

Vaccination rates are high in Australia, around 94 per cent of the eligible population have had at least two boosters, Associate Professor Miller said.

The vaccines have proved effective for limiting the severity of new variants like Omicron, but are less effective at slowing transmission, she said.

With a virus as infectious as XBB.1.5, Associate Professor Miller said "even if only a small proportion become ill or die, it's still a substantial number of people that will have really serious outcomes".

Associate Professor Miller said the public's appetite for another lockdown was low but that a return to mask mandates could prove effective.

"I think wearing masks is the best we can hope for," she said.

University of the Sunshine Coast nursing lecturer Matthew Mason said "people shouldn't be scared, we know what works".

"Stay at home if you're sick, put on a mask when you go into crowded areas," he said.

"One public health measure, we never achieved, was ensuring we had adequate ventilation," Associate Professor Miller said.

Research shows air filtration systems are highly effective at lessening infection risks and hospitals, GP clinics, schools, offices and shopping centres should provide filtered or fresh air to reduce virus transmission, Mr Mason said.

"If we do that we'll reduce, not only COVID-19, but a whole range of other respiratory viral illnesses," he said.

Mr Mason said most Australians care about drinking clean water and "we need to start thinking about air in the same way".

- with Australian Associated Press