A new Covid sub-variant is making headlines around the world right now.
Dubbed XBB, it has been already been found in 17 countries.
So far, it has successfully evaded drug therapies and vaccines by working around the body’s immune system – potentially making it a more potent strain than its predecessors.
But, the most damaging elements of this sub-variant is that scientists expect it be just one of many which could emerge at the same time this winter.
Here’s what you need to know.
What do we know about XBB?
XBB is causing concern among scientists after being detected in Europe, Asia and Australia.
It is believed to come from BA.2, a sub-variant of Omicron. It can evade protective antibodies generated by a breakthrough BA.5 infection, meaning booster jabs could be rendered ineffective.
XBB is spreading rapidly in Singapore in particular, having pushed Covid cases from 4,719 on October 9, to 11,732 on October 10, according to data from Johns Hopkins’ Coronavirus Resource Centre.
Cases have remained above the 9,000 threshold since October 11, and Channel News Asia has reported that 54% of local cases are now XBB.
However, the country expects this wave to be “short and sharp”, averaging at around 15,000 daily cases by mid-November – although it could peak at around 20,000 on some days.
Singapore also claims it was allegedly found in India in August and cases were reported in Hong Kong during the first week of October.
How concerned should we be?
Judging from the data emerging in Singapore, this could be the country’s second biggest Covid wave after the Omicron sub-variant BA.2.
However, the health ministry has also pointed out that “there is no evidence that XBB causes more severe illness” – and the country has a high vaccine uptake rate.
While early signs suggest it is more resistant to antibody treatments, the world is starting to create more boosters which broader protection, by producing vaccines with half the original vaccine and half protection against the dominant strains BA.4 and BA.5.
Lead respiratory virus immunology specialist Natalie Thornburg, the US organisation, Centres for Disease Control and Prevention, also said in a webinar this week: “XBB is a chimera. I think there have been a couple of sequences identified in the US. But it’s way, way, way, way below that 1% threshold. I mean, it’s really like a handful of sequences.”
Is this the only sub-variant people are talking about?
Unfortunately, no – and that’s the problem.
BQ.1, a close cousin is spreading in North America, Europe and Africa, Europe and parts of the US, and also a descendant of Omicron BA.2.
Then there’s its sibling BQ.1.1, which is taking off in Europe and North America.
Together, the two sub-variants account around 11% of viruses sampled in the US according to last week’s data from the US Centers for Disease Control and Prevention (CDC).
Despite this, Anthony Fauci, the US director of the National Institute of Allergy and Infectious Diseases, pointed out that the US is “still in a downward trend”.
BA.2.75, BA.2.75.2, BF.7 and BA.4.6. too – although they all account for very small proportion of total cases.
BA.2.75 is said to be “at least as contagious as our current BA.4 and BA.5”, according to Dr William Schaffner, professor of preventive medicine in the department of health policy at Vanderbilt University Medical Centre – but it’s too early to know.
It may also be able to evade some of the protection from current vaccines, meaning those who have been booster can get infected, but only mildly. It’s taking off in South Asia, while BA.4.6 and BF.7 are in the US.
And, like all Covid sub-variants, any of these infections could cause long Covid.
How are scientists approaching these new variants?
Well, it’s definitely a concern for so many variants to be circulating at once.
But, as Dr Schaffner also told HuffPost: “The World Health Organisation has a worldwide surveillance mechanism underway that keeps looking for new strains of [Covid] and new strains of influenza.”
This means WHO can monitor emerging variants and sub-variants.
And, changes are to be expected – viruses generally mutate so they can stay contagious and spread to more people.
However, Schaffner claimed that the new variants are “quite similar to their virus parents but they may have slightly altered characteristics.”
Instead, scientists now watch hot spots in the actual virus molecule which are changing rapidly, to try to predict how the variants overall are evolving, rather than focusing on individual strains.
For instance, a lot of these mutations are in the receptor binding domain (in the spike protein where antibodies dock). if they can’t land on the virus, they can’t block it.
Jesse Bloom, expert on viral evolution at the Fred Hutchinson Cancer Centre in Seattle, told The Washington Post: “It’s important for people to understand that the fact there’s not a Greek letter name that has come out does not mean the virus stopped evolving.”
Are scientists worried?
Speaking to HuffPost, Dr Catherine Blish, a professor of infectious diseases at Stanford Medicine, also pointed out that previous Covid variants often flare up – and then disappear.
“Nobody thinks about lambda and mu, and those were other variants that [came] up, but they didn’t have enough of a survival advantage to persist,” she said.
This isn’t a universal approach though.
Dr Eric Topol, professor of molecular medicine at Scripps Research, told Fortune “this is different”.
He warned: “Now we have variants with extreme levels of immune evasion and in any given country, potentially a few that could be in play at the same time.”