Moritz Gerstung Profile picture
Nov 18, 2021 β€’ 13 tweets β€’ 7 min read β€’ Read on X
An update on 🦠 SARS-CoV-2 variants in England.

Today: AY.4.2.1, AY.98 and other introductions.

TLDR: It seems to be ok.
Background: The list of Delta sublineages has gotten longer – more than 121 AY.x lineages + sublineages.

This is thanks to the virus hunters @PangoNetwork spotting epidemiologically relevant variants across the 🌍.

These appear as colored branches at cov2tree.org
In England, @CovidGenomicsUK operates a very systematic sequencing programme, which allows to detect & characterise the spread of new lineages early.

Every Monday @jcbarret and his team release data from around 25,000 samples (~10% of cases) on covid19.sanger.ac.uk
In order to shorten the 2-3 weeks between lineage spotting and annotation, @theosanderson has developed a tool that rapidly assigns genomes to the very latest lineages.

(I mention this because the data is slightly ahead of Monday's release using official annotation.)
This latest, provisional data includes a number of new lineages down to AY.120.2.1.

We have been using the model by @harald_voeh to track the fate of 278 lineages. nature.com/articles/s4158…
The first lineage to mention is AY.4.2.1, the purple emerging clade within the green AY.4.2 branch, spotted by @CorneliusRoemer.

It comprises ~3400 samples by now and is found in all English regions, comprising between 1% and 4% of samples in the week ending 6 Nov.
AY.4.2.1's growth was, on average, ~1% faster per day compared to AY.4.2. In some regions it was about the same as AY.4.2.

πŸ‘©β€πŸ”¬: AY.4.2.1 has spike mutation V36F, which could be a hint of a mechanism. But r=1% is within the typical range of fluctuations, so it's inconclusive.
Another new lineage is AY.98 (green), which is rather numerous (n=11k samples) now comprising between 2%-5% of samples.

πŸ‘¨β€πŸ’»: AY.98 is in fact a rather old branch of Delta and has been added mostly to complete the taxonomy.
It has been increasing slowly in all regions except the North East, where it's stagnant at higher levels. πŸ€”

πŸ§‘β€πŸ«: AY.98 was among the first founders of the Delta wave in N/E, reaching high numbers by chance. It now slowly diffuses to other regions until the frequencies are equal.
Lastly, there are also many currently uncharacterised variants across the 🌍.

As the pandemic accelerates in regions such as Eastern Europe, variants from such places also appear in the UK in increasing numbers.
One example is the pink branch below, defined by Orf3a:202L. It doesn't have a pango lineage name yet.

The branch is prevalent in Eastern Europe (πŸ‡©πŸ‡ͺ: 6-10%, πŸ‡΅πŸ‡±: ~10%, πŸ‡ΉπŸ‡· 20-30%). But the relative proportions there are fairly stable, arguing against a large growth advantage.
In England Orf3a:202L is mostly found in London, where it rose noticeably to around 80 cases (2%) per day. These numbers are comparable to AY.4.2.1; the growth was even faster. 😳

πŸ‘©β€πŸ’»: The increase mostly reflects the rising cases elsewhere rather than an inherent advantage.
So overall, the situation in England seems to be in a fluent state, as expected.

The spread of most lineages reflects the stochastic and complex domestic and international dynamics of the pandemic.

AY.4.2.1 may have a very small growth advantage, but I wouldn't bet on it yet.

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More from @MoritzGerstung

Jan 21, 2023
There are some signs now that XBB.1.5 is loosing steam as it spreads through the wider population.

The share of cases has increased more slowly in the US and UK, recently.

A speculative thread why this might be.
In slowing down XBB.1.5 follows a pattern that has been noted also for BQ.1.1 or XBB.1.1.

Their initial fitness (daily increase of variant share) was higher than their long term advantage in a multi-lineage model with constant differences between variants (coloured lines).
In fact this slowing was observed for almost every Omicron lineage.

There is large variation between countries though, in part because of the low numbers at low incidence.

But the trends are clear that the initial growth rates dropped down on average between 0.02 to 0.04.
Read 12 tweets
Jan 3, 2023
A global look at the XBB.1.5 SARS-CoV-2 variant, which has spread rapidly in the US.
In the US its share doubled every ~8 days during the past 2.5 months and is now estimated to contribute more than 30% of cases.

Across the globe XBB.1.5 is still comparably rare (<5%).
XBB.1.5's share is rising globally, too.

However, it spreads slightly slower than in the US with relative doubling times between 8-15 days.

This makes XBB.1.5 currently the fastest spreading lineage, followed by CH.1.1.

It could possibly replace BQ.1.1.
Read 10 tweets
Nov 27, 2022
A closer look at SARS-CoV-2 variants across countries and continents:

- The competition between BQ.1*, XBB*, and BA.2.75.* inc. BN.1 & CH.1.1 remains open

- BQ.1* is more prevalent in the Western, and XBB* & BA.2.75.* in the Eastern hemisphere.
Europe and North America see high frequencies of BQ.1*.

So far there hasn’t been a major upswing of cases.

Europe saw a wave of BA.5.2 in September which stalled the spread of BQ.1*.
Parts of South America appear to see an increase of reported cases attributable to BQ.1*
Read 12 tweets
Nov 17, 2022
Some musings on SARS-CoV-2 evolution

TLDR: The share of the variant zoo increased further with BQ.1* and XBB* at the top.

But there are interesting patterns underneath which can be illustrated by one exotic lineage: CH.1.1.

It’s rare, but it rises as fast as BQ.1.1. Why? ImageImage
Background: There is a whole zoo of omicron sublineages, often defined by a range of mutations enabling partial immune escape.

Looking at the crude global increase over the past 28d CH.1.1 is one that has increased at the upper end of the flock. Image
Why does it spread as fast as BQ.1.1?

It turns out that it has independently acquired *the same set of key RBD mutations* as BQ.1.1.

Yet CH.1.1 derives from BA.2, while BQ.1.1 is a descendant of BA.5 though. Image
Read 10 tweets
Nov 4, 2022
The current SARS-CoV-2 variant situation in Germany:

* BQ.1 prevalence ranges between 5 to 12% across states,
* BQ.1.1 ranges from 5 to 15%.

The total share is around 18%. ImageImage
In line with international observations BQ.1.1’s growth advantage to other lineages is slightly lower than initial estimates suggested.

Image
Its current doubling time has come down to around 14d, also because of of competition with other lineages. Image
Read 7 tweets
Nov 4, 2022
A brief update on global SARS-CoV-2 variants:

* BQ.1.1 spreads, albeit at the low end of expectations
* XBB* and BQ* lineages are the most widespread
* Further new variants have been defined, including CK.2.1.1 leading to complex patterns
While the initial estimates of BQ.1.1's growth advantage to BA.5 were between 10-15%, the estimate has come down to ~10% more recently.

As other more transmissible variants such as BF.7 have also spread the current fitness is lower, around 6-7%.
CK.2.1.1 came a bit out of the blue but is also contributing a measurable share of cases in countries such as Spain (~9%) and Germany (~3%).

It spreads at a similar rate as BQ.1, which it also matches in terms of key RBD mutations as shown below

Read 7 tweets

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