Scientists are keeping a 'close eye' on a mutation of the Delta variant that has been seen in a growing number of coronavirus cases.
The AY4.2 variant is being monitored by government officials but has not yet been classified as a variant of concern (VOC) or a variant under investigation (VUI).
According to data from the UK Health Security Agency (UKHSA), the sublineage of the Delta variant is 'currently increasing in frequency', and an estimated six per cent of Covid-19 cases genetically sequenced during the last week of September were of a new type.
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The AY4.2 variant, first identified in July, contains the mutations A222V and Y145H, both of which have been found in various other coronavirus lineages since the beginning of the pandemic, the UKHSA said.
Downing Street has insisted there is no evidence the variant spreads more easily than others, but said it was "something we’re keeping a very close eye on".
“There’s no evidence to suggest that this variant … the AY4.2 one … is more easily spread," a spokesperson for No 10 said.
“There’s no evidence for that, but as you would expect we’re monitoring it closely and won’t hesitate to take action if necessary.”
The first strains carrying both the A222V and Y145H mutations were sequenced as early as April 2020.
Francois Balloux, professor of computational systems biology at University College London and director of the UCL Genetics Institute, explained: “The A222V was found in the B.1.177 lineage that swept Europe in the summer of 2020, but careful follow-up analyses pointed to the lineage likely having no inherent transmissibility advantage and that its spread was most likely caused by demographic processes.”
He added that neither mutation was an obvious candidate for increased transmissibility, but that mutations can have different, sometimes unexpected, effects in different strains.
“As AY.4.2 is still at fairly low frequency, a 10 per cent increase in its transmissibility could have caused only a small number of additional cases," Prof Balloux said.
“As such it hasn’t been driving the recent increase in case numbers in the UK.”
He said the emergence of another more transmissible strain would be “suboptimal”, adding: “This is not a situation comparable to the emergence of Alpha and Delta that were far more transmissible (50 per cent or more) than any strain in circulation at the time.
“Here we are dealing with a potential small increase in transmissibility that would not have a comparable impact on the pandemic.”
Tests are currently underway to determine how much of a threat the variant may pose, and whether it has an advantage over the vaccines.
