It’s likely several new sub lineages of the COVID-19 virus are already circulating in Australia.
That warning comes as health authorities prepare for a potential spike in cases towards the end of the year.
Any wave of new infections won’t be helped by the scrapping of most remaining public health orders to restrict transmission of COVID-19, as agreed by state and federal governments in October’s national cabinet meeting.
While restrictions for certain settings (such as hospitals, health care, disability and aged care facilities) are still in place, self-isolation requirements – previously set at a compulsory five days for positive cases – have been abolished.
Now with the emergence of new sublineages of the Omicron variant around the world, health authorities are preparing for more cases.
Although some of these newly evolving versions of the virus are receiving little media attention in Australia, Dr Ash Porter from the Doherty Institute tells Cosmos they have arrived in the country already.
“Pretty much all of them are [likely to be in Australia], and they’re going to be circulating,” Porter says.
“And if they’re not here yet, they will be very soon.”
Porter researches the evolution of zoonotic viruses, such as coronaviruses, and has been involved in work to sequence COVID-19 genomes in Australia. The reduction in public resources allocated to monitoring viral genomes has made it challenging for Porter and their colleagues to precisely say which other Omicron subvariants have arrived, but they say it’s only a matter of time before all appear.
The grandchildren of Omicron
Dubbed the ‘scrabble’ variants by parts of the US media for their nomenclature using the board game’s high value letters B, Q and Z, these variants have been circulating in several nations and are starting to increase their share among hospitalisations overseas.
Omicron BA.5 accounted for 70% of cases in the US in the week ending 15 October. A fortnight later, and its estimated share is below 50%, with BQ.1 and BQ.1.1 experiencing almost exponential growth in case numbers to account for almost 3 in 10 infections.
These BQ sublineages were recently labelled by the director of the US National Institute of Allergy and Infectious Diseases, Dr Anthony Fauci, as being “troublesome” for their ability to evade immunity from vaccination or previous infection.
“When you get variants like [BQ], you look at what their rate of increase is as a relative proportion of the variants,” Fauci told CBS News.
“This has a pretty troublesome doubling time.”
XBB and BQ variants have both been detected in the eastern states. The former is of particular interest to Porter due to its recombinant nature. This occurs when a person is infected with two different strains of a virus. Inside a host cell, these viruses exchange and recombine their genetic information to effectively create a new genome.
This doesn’t necessarily mean the virus is more powerful, or likely to bestow more serious illness on a host. In the case of XBB, however, it might mean it’s better able to infect a person.
“They just chuck all their DNA in there,” Porter says of what happens when a virus infects a cell.
“If you’ve got two different lineages infecting you, and doing that to the same cell, it’s a way for them to switch around their DNA and combine it.
“If you have a lineage that’s really transmissible and a lineage that’s really virulent, and they both co-infect one cell, they can give each other the most advantageous bits of the DNA.
“There’s been a lot of preprint [research] that have suggested XBB is the most immune-evasive lineage to date.”
Public health preparing for spike in cases
With authorities previously projecting another wave of COVID-19 infections to take place in November, it would seem the emergence of these new sub lineages has come at an inopportune time for Australia.
But while there are suggestions XBB and BQ might be better at dodging vaccine immunity, these don’t necessarily consider hybrid immunity where people have been both vaccinated and infected with a previous variant.
And while a future wave seems probable, behavioural scientist and vaccination expert at the University of Sydney Professor Julie Leask says the barriers to its impact have waned.
They include a glacial uptake of existing boosters, which now include bivalent vaccines based on the original Omicron strain, and a legislated requirement to isolate if infected.
Leask emphasises that the absence of compulsory isolation requirement does not mean it isn’t necessary. Rather, she points to governments continuing to recommend people stay home when infected.
“I think it’s fair to say we’re very likely to get another wave before Christmas, the magnitude of that wave is the burning question, in the face of a higher level of population hybrid immunity from both infection and vaccine,” Leask says.
“We do have to find that sweet spot where people continue to engage in those appropriate preventative behaviours, and staying home when you’ve got respiratory symptoms – particularly at the beginning of the illness – is very helpful for protecting other people.
“[Governments] have taken away the requirement [to isolate], but they haven’t taken away a strong recommendation. That’s the same thing we have in vaccination of adults and with most other vaccines – it’s a strong recommendation.”
At present, more than 95% of eligible Australians have received their first two vaccine doses, however current advice suggests that the effectiveness of those vaccines wanes over time and requires a third dose – or ‘booster’ – to top-up immunity.
More than 70% of eligible people have received a third dose, but only 41% have received a fourth dose.
Matthew Agius is a science writer for Cosmos Magazine.
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