After a period of relative calm in terms of the coronavirus鈥檚 evolution, further notable variants are now emerging. An offshoot of the delta variant, known as AY.4.2, appears to be slightly more infectious than the original delta, and could slowly replace it. Several other new variants are being monitored, including one that seems to have evolved undetected in Central Africa before spreading to Europe and beyond.
None of these emerging variants appear to be hugely more infectious or better at dodging immunity than delta, so aren鈥檛 expected to trigger major waves of cases around the world. But the bad news is that it may be only a matter of time before such a variant evolves.
鈥淪omething with delta-like transmissibility, but which escapes immunity better, is entirely possible, and in fact it may even be inevitable eventually,鈥� says Tom Peacock at Imperial College London.
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The SARS-CoV-2 coronavirus has been constantly mutating since jumping to people from animals, but most mutants die out. Only a few new variants have a significant advantage over competing variants. The alpha variant was around 50 per cent more transmissible than older variants, and caused a wave of new cases as it spread worldwide early this year. Then came delta, which was around 50 per cent more transmissible than alpha, and triggered yet another global surge in cases.
Delta has been outcompeting other variants in country after country, driving most of them to extinction. There are only a few 鈥渋slands鈥� of older variants left, says Peacock.
The dominance of delta temporarily slowed down the evolution of dangerous new variants by reducing the diversity of the virus 鈥� with less genetic diversity, the virus has less opportunity to evolve. But delta itself is now spawning new variants and diversifying.
One of the new variants is AY.4.2. It has been designated a 鈥渧ariant under investigation鈥� by the UK Health Security Agency (UKHSA), which is monitoring it, but hasn鈥檛 yet been named a 鈥渧ariant of interest鈥� by the World Health Organization, and so hasn鈥檛 been given a name from the Greek alphabet.
AY.4.2 has a couple of extra mutations in the outer spike protein of the virus. The effect of these mutations isn鈥檛 clear, but in the UK it has been slowly gaining ground and accounted for at the beginning of November. It appears to be slightly more infectious than delta.
Fortunately, AY.4.2 appears to be no better at dodging immunity than the original delta. 鈥淭he vaccines work against all the variants we have seen emerge so far,鈥� says Meaghan Kall at the UKHSA. 鈥淭here is always the potential for that to change, though.鈥�
AY.4.2 doesn鈥檛 appear to cause more severe disease, either. In fact, one study in the UK suggests . But more studies are needed to confirm this, say some virologists. 鈥淭his may likely turn out to have been a 鈥榝alse positive鈥� finding,鈥� at University College London.
The UK may be the first to notice an uptick in cases linked to AY.4.2 because its virus surveillance is more comprehensive than those of other countries, says Peacock. The variant is likely to be gaining ground in many other countries too, spawning yet more variants along the way, he says.
In fact, an offshoot called AY.4.2.1, with an extra spike mutation, in England, but it isn鈥檛 possible to be sure of this so early on. 鈥淚 wouldn鈥檛 say anything on the horizon right now is very concerning,鈥� says Kall. 鈥淭he reason that AY.4.2 is being very closely watched is that it may not take very much for one of these sublineages to gain mutations that do make it worse.鈥�
There is also concern about another new variant, called B.1.640, which Peacock helped identify in October. It might be the only non-delta variant capable of competing with delta. It was first detected in the Republic of the Congo.
鈥淭his is the first [non-delta variant] we鈥檝e seen growing in a country that has a background of delta,鈥� says Peacock.
What鈥檚 striking about B.1.640 is that it isn鈥檛 closely related to any other variants and already has a lot of genetic diversity, says Peacock. This suggests it has been circulating undetected for quite some time, probably in central Africa.
Its properties haven鈥檛 yet been studied, but it has a lot of the same mutations as , which is very good at dodging immunity, says Peacock. C.1.2 is still around but isn鈥檛 gaining ground versus delta.
B.1.640 has now been detected in several European countries and Canada, but this apparently rapid spread might be due to a super-spreader event at a school in France rather than any inherent advantage over other variants, says Peacock. It is too early still to tell if it can compete against the delta lineages.
鈥淧re-delta, this might have been a beast. Post-delta, I don鈥檛 really know鈥︹�� .
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