Through routine scanning of variation in Delta, a small number of sequences were detected which had acquired the spike protein mutation K417N. Information suggests that there are at least 2 separate clades of Delta with K417N. One clade is large and internationally distributed with PANGO lineage designation AY.1. A second clade found in sequences uploaded to GISAID from the USA, now designated AY.2.
As of 16 June 2021, 161 genomes of Delta-AY.1 have been identified on GISAID. from Canada (1), India (8), Japan (15), Nepal (3), Poland (9), Portugal (22), Russia (1), Switzerland (18), Turkey (1), USA (83).
There are currently 38 cases of Delta-AY.1 in England (36 confirmed sequencing and 2 probable genotyping). Cases have been detected in 6 different regions in England. Delta-AY.2 has not been detected in England.
UK Variants of Concern Technical Briefing 15 (PDF download)
According to Bani Jolly of the Institute of Genomics and Integrative Biology, the phylogeny of Delta has two separate clades. While AY.1 is found in a few countries including the UK, India and Nepal, the other clade (AY.2), is largely from the sequences from California (USA).
“The split between the two clades seems to be based on two spike mutations — A222V and T95I. While all sequences in the California cluster share spike A222V, all sequences in the larger international cluster share spike T95I,” Jolly tweeted.
Stating that AY.1 has arisen independently a number of times and could be more prevalent than observed in countries with limited genomic surveillance, she tweeted that given that Delta is a variant of concern, it is important to take note of any sub-lineages that may emerge.