At the time, many were sceptical that A222V conferred an advantage. A222V was previously seen last year in the B.1.177 lineage that probably emerged in Spain and was then spread across northern Europe, most likely by holidaymakers. It has also been observed in a few European nations: Denmark, Germany and Ireland, to name a few.īut whether its two mutations offer the virus a selective advantage is unclear as well. The spike protein is a key part of the virus’s outer surface, and is the part of its structure that it uses to get inside cells.ĪY.4.2 has grown steadily in volume to the point where it now accounts for about 9% of UK cases in the last 28 days. It’s defined by two additional genetic mutations, Y145H and A222V, that affect the spike protein. This brings us to AY.4.2 – a sub-lineage of AY.4 – which was first noted at the end of September, though it appears it surfaced in the UK around June. However, the impact of this mutation is unknown.
The defining change in AY.4 is the mutation A1711V, which affects the virus’s Nsp3 protein, which plays a number of roles in viral replication. Sometimes, for a certain form of a virus to dominate, it doesn’t have to be better than others – it simply needs to be in the right place at the right time.īut, given its rise to dominance in the UK, AY.4 might well have a selective advantage. If it infected a sizeable number of people, who later infected others, this may have quickly built up a large amount of virus all from the same origin. This lone virus would have been the “founder”, the only virus spreading at the event. With COVID, this might have happened by there being a single case at a large event. In the area where the separated viruses are, all subsequent viruses will therefore be descendants of this subset. This is when a subset of viruses get separated from the overall viral population, and then reproduce in isolation. One of these – AY.4 – has been steadily growing in proportion in the UK over the last few months, accounting for 63% of new UK cases in the last 28 days.ĭoes AY.4 have an advantage? We’re still not sure if AY.4’s mutations confer a genuine advantage or if the increasing frequency of the lineage is simply down to what’s called a “founder effect”. There are now 75 AY lineages identified, each with different additional defining mutations in their genome. So the AY forms of the virus aren’t vastly different from what’s come before, even though their labelling is different. Once a lineage’s labelling gets five levels deep, a new letter combination is started to avoid the name getting too long. What we were reporting to colleagues in Cog-UK was classified the following week as B.1.617.2, one of three main sub-lineages of B.1.617, and which was later named delta by the World Health Organization.ĪY is a further evolutionary step forward from here. Variants are distinguished by the different mutations they have in their genetic material and, looking at the mutations in our samples, it appeared our cases were missing some of the commonly accepted mutations of B.1.617 but also had some additional ones. Our team in Northumbria, working as part of Cog-UK – the British consortium that sequences the genomes of COVID samples to see how the virus is changing – had just sequenced two samples connected via travel history to India.Īt the time we knew the lineage circulating in India was B.1.617, but the cases we had sampled didn’t match this.
If we go back to April of this year, we can trace the origins of AY.4.2. They are overseen by the diligent Pango network, a joint team of researchers from the universities of Edinburgh and Oxford, who act as the custodians of lineages and handle the assignment of new ones. These are labels given to branches of the COVID evolutionary tree to illustrate their relatedness. But what is it, where did it come from, and should we be concerned? AY.4.2 is what’s termed a “lineage”. By Matthew Bashton and Darren Smith, Northumbria University, Newcastle Newcastle, Oct 26 (The Conversation) No sooner than you thought all the talk of new COVID variants was over, there’s news of yet another one: AY.4.2.