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In late October, the UK Health Security Agency assigned variant designations to 2 new omicron “grandchildren”: BQ.1 and XBB. This means they are going to be monitored by well being authorities, however should not 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 dad or mum of BA.5 (the variant presently 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 title starting with an “X” (like XD, XE and XF).
But what can we make of those variants? Are they trigger for concern? Let’s have a look first at how they’re spreading.
In the UK, Europe and North America, the prevalence of BQ.1 is rising shortly. Recent knowledge from the UK’s Office for National Statistics (ONS) estimated BQ.1 sub-lineages (together with BQ.1 and the same BQ.1.1) made up 16.7% of infections. In the US, BQ.1 and BQ.1.1 collectively make up round 35% of infections.
XBB appears to be extra prevalent in Asia. While the ONS knowledge suggests it makes up solely 0.7% of infections within the UK, in Singapore some 58% of just lately sequenced instances are XBB. But whereas sequences of XBB are rising globally, XBB instances 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.
Read extra:
Omicron XE is spreading within the UK – a virologist explains what we find out about this hybrid variant
What are the variations between BQ.1 and XBB?
Omicron variants are profitable due partly 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 be the goal of antibodies that are an vital a part of the immune response.
A latest preprint (a research but to be peer-reviewed) means that mutations inside the receptor-binding area may also help XBB escape neutralising antibodies generated by COVID vaccines or an infection with earlier omicron offshoots, together with the dad or mum strains BA.2 and BA.5. This preprint regards XBB as one of the vital 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 instructed that a lot of these particular adjustments within the receptor-binding area can enhance the virus’s development effectivity, or “health”. The concept is that extra adjustments enable it to connect to human cells extra strongly, giving it a greater probability of infecting that cell.
According 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 capability to strongly connect to human cells. XBB is presently the one variant at degree 7, with seven of the 21 key mutations.
At the second that is simply an commentary and hasn’t been formally revealed or peer reviewed. However, different scientists have additionally famous XBB’s obvious development benefit over different variants.
Read extra:
What are the signs of omicron?
But 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 known as the N-terminal area as effectively.
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 sturdy immune responses to this a part of the spike protein. Preliminary proof suggests XBB may be very efficient at evading these antibodies too. This signifies that earlier an infection with BA.2 or BA.5 may not shield you from XBB.
Should we be fearful about XBB?
By these metrics, XBB is doubtlessly extra immune evasive than BQ.1 and its dad or mum BA.5, and may need a development benefit which might enhance virus unfold.
The excellent news is that based mostly on Singaporean knowledge, XBB has been estimated to have a 30% decrease threat of hospitalisation in contrast with BA.5. But we don’t but have knowledge to assist this from different international locations, so this would possibly change as XBB turns into extra widespread.
It is feasible that we might 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 towards XBB. Only 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 Trust, Cancer Research UK and GCRF. She is affiliated with the University of Leeds and is a member of the Microbiology Society.
