A post on the AY.4 sub-lineage of the Delta Sars-Cov-2 variant. Also known as B.1.617.2.4, this sub-lineage hasn’t received a lot of press attention yet, but it seems to have become the biggest sub-lineage of Delta across the globe so far.
In the USA, the Delta AY.4 sub-lineage is currently appearing in about 20% of sequences (light blue area) according to Outbreak.info:
In the UK, AY.4 currently appears in about 46% of samples (light blue area), and is now outcompeting B.1.617.2 (dark blue area).
AY.6 seems to be coming up on the rails though at 3%:
In Australia, AY.4 (dark blue area) clearly predominates over B.1.617.2 (light blue area) with 67% of sequences, B.1.617.2 is at 16% and AY.12 is at 10% :
In the USA, the estimated number of AY.4 cases was over 80,000 in early August 2021:
In the UK, the estimated number of AY.4 cases was about 13,000 in late August 2021
In Australia, the estimated number of cases was over 600 in late August 2021
In the USA, the demographics for AY.4 show it spreading across almost all age ranges,
But in the UK, AY.4 seems to be spreading amongst young children:
And in Australia, AY.4 seems to be spread across all age ranges:
The global reach of the AY.4 sub-lineage is really quite astounding considering it’s relatively recent appearance:
Further reading: New AY lineages and an update to AY.4-AY.12