AY.4 Delta sub-lineage now predominant in UK and Australia, rising in the US

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:

AY.4 Delta Sub-lineage at 19 percent of sequences in the USA


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%:

AY.4 Delta Sub-lineage at 46 percent of all UK sequences


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% :

AY.4 Delta Sub-lineage at 67 percent of sequences in Australia


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


Many thanks, as always, to the teams at Outbreak.info and covSpectrum.org for their hard work in compiling this data.




Image by Free-Photos from Pixabay

Delta attempting to brute-force its way past the human immune system

The Delta variant of Sars-CoV-2 seems to have taken a leaf from a computer hacker’s manual by attempting to brute-force its way past human and vaccine immunity systems by spitting out slightly mutated versions of itself almost on a daily basis.

Similar to cracking a password, brute-forcing means that the virus is trying every possible combination of variations to find the most effective one, and it’s doing it incredibly quickly. The most successful new mutations then become dominant through selection pressure.

Many of these new Delta plus variants are distinguishable only by a single mutation, but the brute-force technique the virus is now using represents the biggest threat to humanity so far, as we have no obvious means to prevent it.

For example, two weeks ago, we took a snapshot of Outbtreak.info that showed a big rise in the AY.3 Delta plus variant in the USA.


Now, just two weeks later, the AY.3 variant has already been supplanted by the AY.4 variant:




The number of Delta plus variants seems to be rising ever more quickly, each variant with its own individual key combination to try to pick the immunity lock. With no lockout mechanism for failed attempts, the virus can just keep trying until it succeeds.

Here’s a list of the Delta Plus variants so far, taking us up to AY.15, with many more to be added soon we’re sure:

AY.1 United States of America 44.0%, Portugal 10.0%, United Kingdom 10.0%, Japan 10.0%, Switzerland 7.0% 2021-04-07 243 562 Alias of B.1.617.2.1, in several European countries, from pango-designation issue #95

AY.2 United States of America 99.0%, Mexico 0.0%, Spain 0.0%, Aruba 0.0%, Albania 0.0% 2021-03-31 201 1232 Alias of B.1.617.2.2, in USA with K417N, from pango-designation issue #107

AY.3 United States of America 98.0%, Mexico 1.0%, United Kingdom 0.0%, Japan 0.0%, Germany 0.0% 2021-04-13 846 7503 Alias of B.1.617.2.3, USA lineage, from pango-designation issue #121

AY.3.1 United States of America 100.0%, India 0.0% 2021-05-18 197 983 Alias of B.1.617.2.3.1, USA lineage, from pango-designation issue #147

AY.4 United Kingdom 68.0%, United States of America 12.0%, Denmark 3.0%, Spain 2.0%, France 2.0% 2021-01-05 3684 152304 Alias of B.1.617.2.4, UK lineage, from pango-designation issue #180

AY.5 United Kingdom 68.0%, Portugal 12.0%, Spain 4.0%, France 4.0%, Ireland 3.0% 2021-04-15 436 6837 Alias of B.1.617.2.5, UK lineage, from pango-designation issue #180

AY.6 United Kingdom 79.0%, United States of America 8.0%, Ireland 2.0%, Italy 2.0%, Denmark 1.0% 2021-01-08 201 7007 Alias of B.1.617.2.6, UK lineage, from pango-designation issue #180

AY.7 Denmark 71.0%, United Kingdom 23.0%, Italy 3.0%, France 1.0%, Germany 1.0% 2021-05-01 134 6417 Alias of B.1.617.2.7, UK lineage, from pango-designation issue #180

AY.7.1 4624 0 Alias of B.1.617.2.7.1, Denmark lineage

AY.7.2 342 0 Alias of B.1.617.2.7.2, predominantly Italy lineage in multiple other European countries

AY.8 United Kingdom 100.0%, Australia 0.0%, Belgium 0.0% 2021-04-20 703 707 Alias of B.1.617.2.8, UK lineage, from pango-designation issue #180

AY.9 United Kingdom 64.0%, Denmark 11.0%, Germany 5.0%, Switzerland 4.0%, Belgium 3.0% 2021-04-01 322 6892 Alias of B.1.617.2.9, UK lineage, from pango-designation issue #180

AY.10 United Kingdom 73.0%, Canada 8.0%, United States of America 7.0%, Gambia 5.0%, France 2.0% 2021-04-12 71 771 Alias of B.1.617.2.10, UK lineage, from pango-designation issue #180

AY.11 United Kingdom 33.0%, United States of America 16.0%, South_Africa 11.0%, Turkey 10.0%, Ireland 6.0% 2021-02-06 522 2138 Alias of B.1.617.2.11, UK lineage, from pango-designation issue #142

AY.12 Denmark 11.0%, United States of America 11.0%, United Kingdom 10.0%, Germany 10.0%, Israel 7.0% 2020-09-07 579 26845 Alias of B.1.617.2.12, Israel lineage, from pango-designation issue #170

AY.15 94 0 Alias of B.1.617.2.15, Canada lineage

Lineage information courtesy of cov-lineages.org


USA: AY.3 genomes increasing faster than Delta B.1.617.2