Thread by @TheLawyerCraig

Got a bit curious about the US v. UK as it relates to the #DeltaVariant. Some good news on that front for the US: at least in the early stages, the US rate of increase is nowhere near the UK.

🧵thread🧵

First: I used covariants.org/per-country, which shows percentage of sequenced variants based on 2-week blocks. One potential point of confusion to note when you use the site: the dates along the x-axis indicate the *start* of the 2-week period.

Here are the percentages of sequences that made up the #DeltaVariant in the UK (by 2-week period):

3/22-4/04: 0.09%
4/05-4/18: 1.45%
4/19-5/02: 8.92%
5/03-5/16: 33.17%
5/17-5/30: 72.58%

Here are the percentages of sequences that made up the #DeltaVariant in the US (by 2-week period):

3/22-4/04: 0.03%
4/05-4/18: 0.25%
4/19-5/02: 1.01%
5/03-5/16: 2.26%
5/17-5/30: 5.28%

You can see that the US started out maybe 2-2.5 weeks behind the UK. And the closest comparison point is that the UK sequenced 1.45% during the 2-week period prior to the US sequencing 1.01%. But the 4 weeks that followed diverged sharply. But that doesn't tell the whole story...

The UK's 7-day average case count began rising in early May and has not yet stopped (though the rate has begun to slow). From 5/2 to 5/30, the UK's 7-day average cases rose 51%. The US during that same period? Cases *fell* 61%.

So, not only is the percentage of #DeltaVariant sequences moving at nowhere near the UK's pace thus far, the US's absolute case count drop v. the UK's rise means the increase in the actual number of Delta cases (if you credit the sequence %'s) is rising at an *even slower* rate.

If you multiply the sequence % by the case counts, the 4 weeks after the UK sequenced the #DeltaVariant at 1.45% saw a weekly rise of ~493% in Delta cases.

For the 4 weeks after the US sequenced Delta at 1.01%, the US saw Delta cases rise ~26% weekly.

Also, I didn't use the most recent 2 weeks because the sequence count is too low (only 124 in the US vs. tens of thousands in prior weeks). Those will backfill in time.

But since 5/30, the US case count has continued to drop (-31% more as of 6/11), while the UK rises.

The "% of cases is doubling every X days" phrasing often comes into play. If there are 20k total cases in Week 1 and 10k in Week 2, and the % of a variant doubles *as a percentage of cases* from W1 to W2, then the # of variant cases remained the same (and other types are fading).

The CDC's variant page seems to line up pretty well with the source above. The 2-week periods are staggered differently and show for the week ending on:

4/10: 0.1%
4/24: 0.6%
5/08: 1.3%
5/22: 2.5%
6/05: 6.1% (*Nowcast projection)

That would provide the following weekly-ish trend interlacing the CDC & CoVariants data:

[4/04] 0.03%, 0.10%, 0.25%, 0.60%, 1.01%, 1.30%, 2.26%, 2.50%, 5.28%, 6.10% [6/05]

The UK took 4 weeks to get from 1.45% to 33.17%, and another 2 weeks to surpass 70%. We just aren't there.

Past performance is no guarantee of future results, of course. But for several weeks the US has not approached the % increase of #DeltaVariant seen in the UK. We went from 2-3 weeks behind to 5-6 weeks behind in terms of % of cases (and even further considering our declines).

The #DeltaVariant harkens a bit back to #B117, which also piqued my curiosity. Here's my thread from early April on that, noting how the variant acted much differently in different regions of the the US (at similar variant saturation):

https://twitter.com/TheLawyerCraig/status/1379053890927263745?s=20

I've said it before, and it bears repeating: as a UGA, Falcons, Braves, and Tottenham fan, I have learned to expect unbelievably negative things to happen when all is trending well. So I take nothing for granted! I just wanted to see what the US v. UK data showed thus far.