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In late October, the UK Well being Safety Company assigned variant designations to 2 new omicron “grandchildren”: BQ.1 and XBB. This implies they are going to be monitored by well being authorities, however aren’t at this stage considered variants of concern.
If we consider the omicron variant as a household tree, BA.2 (the dominant pressure within the UK in spring of 2022) is the mum or dad of BA.5 (the variant at the moment dominant within the UK) and the grandparent of BQ.1. In different phrases, BQ.1 is a sub-lineage of BA.5.
XBB is a hybrid of two omicron BA.2 lineages, BA.2.10.1 and BA.2.75. This makes XBB one other grandchild of BA.2. XBB and BQ.1 are subsequently cousins.
A hybrid variant is created when two totally different sub-variants mix and swap elements of their genetic materials. We’ve seen this occur with the coronavirus earlier than, indicated by a variant identify starting with an “X” (like XD, XE and XF).
However what can we make of those variants? Are they trigger for concern? Let’s have a look first at how they’re spreading.
Within the UK, Europe and North America, the prevalence of BQ.1 is rising rapidly. Current information from the UK’s Workplace for Nationwide Statistics (ONS) estimated BQ.1 sub-lineages (together with BQ.1 and the same BQ.1.1) made up 16.7% of infections. Within the US, BQ.1 and BQ.1.1 collectively make up round 35% of infections.
XBB appears to be extra prevalent in Asia. Whereas the ONS information suggests it makes up solely 0.7% of infections within the UK, in Singapore some 58% of lately sequenced circumstances are XBB. However whereas sequences of XBB are growing globally, XBB circumstances in Singapore now seem like beginning to fall.
Scientists are intently watching a number of areas the place each variants are circulating to see which has the aggressive edge.
Learn extra:
Omicron XE is spreading within the UK – a virologist explains what we learn about this hybrid variant
What are the variations between BQ.1 and XBB?
Omicron variants are profitable due partially to a number of shared mutations within the receptor-binding area of the spike protein (a protein on the floor of the virus which permits it to connect to our cells).
A key distinction between BQ.1 and XBB is the quantity and placement of mutations within the receptor-binding area. This a part of the protein is required for the virus to contaminate our cells, and can also be the goal of antibodies that are an necessary a part of the immune response.
A latest preprint (a examine but to be peer-reviewed) means that mutations throughout the receptor-binding area can assist XBB escape neutralising antibodies generated by COVID vaccines or an infection with earlier omicron offshoots, together with the mum or dad strains BA.2 and BA.5. This preprint regards XBB as probably the most antibody-evasive coronavirus strains we’ve seen.
New COVID variants are popping up on a regular basis.
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Cornelius Roemer, a computational biologist in Switzerland, has urged that numerous these particular modifications within the receptor-binding area can enhance the virus’s development effectivity, or “health”. The thought is that extra modifications enable it to connect to human cells extra strongly, giving it a greater probability of infecting that cell.
In response to Roemer’s mannequin, BQ.1 is a level-5 variant, with 5 mutations from an inventory of 21 key mutations which enhance SARS-CoV-2’s means to strongly connect to human cells. XBB is at the moment the one variant at degree 7, with seven of the 21 key mutations.
In the mean time that is simply an remark and hasn’t been formally printed or peer reviewed. Nonetheless, different scientists have additionally famous XBB’s obvious development benefit over different variants.
Learn extra:
What are the signs of omicron?
Nevertheless it’s not simply mutations within the receptor-binding area that might give XBB an edge. XBB has mutations in one other a part of the spike protein referred to as the N-terminal area as properly.
The immune system additionally targets the N-terminal area with antibodies, and individuals who have recovered from BA.2 and BA.5 infections mount particularly robust immune responses to this a part of the spike protein. Preliminary proof suggests XBB may be very efficient at evading these antibodies too. Because of this earlier an infection with BA.2 or BA.5 won’t defend you from XBB.
Ought to we be anxious about XBB?
By these metrics, XBB is probably extra immune evasive than BQ.1 and its mum or dad BA.5, and might need a development benefit which may enhance virus unfold.
The excellent news is that primarily based on Singaporean information, XBB has been estimated to have a 30% decrease danger of hospitalisation in contrast with BA.5. However we don’t but have information to assist this from different international locations, so this would possibly change as XBB turns into extra widespread.
It’s doable that we may face a double wave of infections within the UK – a wave of BQ.1 infections from Europe and the US, earlier than a second wave of XBB from Asia. And we don’t know if BQ.1 will supply any safety in opposition to XBB. Solely time will inform whether or not XBB will outperform BA.5 or BQ.1, or if one other variant is ready within the wings.
Vikki Easton has beforehand acquired funding from the BBSRC, MRC, Wellcome Belief, Most cancers Analysis UK and GCRF. She is affiliated with the College of Leeds and is a member of the Microbiology Society.
