Ryan Hisner Profile picture
Jan 28, 2022 10 tweets 4 min read Read on X
A thread of BA.2 updates.

BA.2 continues to do its thing in Denmark. The two most recent days of sequencing (January 20 & 21) recorded 74.2% BA.2 (285 of 384 cases). 1/9
The exponential increase in the proportion of BA.2 cases continues in the UK.

The apparent slowdown in growth in the past several days is entirely due to 0 of 8 sequences being BA.2 over the past four days & should therefore be ignored. 2/9
Similar exponential increase in the percentage of BA.2 cases in the US.

Again, the illusory plunge over the last five days is entirely due to a very small number of sequences and should be ignored. 3/9
My home state of Indiana had recorded zero BA.2 cases before last night's update, when six cases were recorded in the most recent week of sequencing, indicating a substantial percentage of BA.2. Major caveat: sample size very small. 4/9
Germany's BA.2 path is similar to what Denmark's was early on. A recent report found that 30% of cases in Berlin were BA.2, so as has been the case elsewhere, large cities with lots of international travelers are leading the way. 5/9
Japan finally has enough BA.2 to provide a decent indication of it's path. Surprise!—it's upward.

(Once again, the tiny sample sizes in recent days mean the illusory plunge at the end should be ignored.) 6/9
Not much sequencing in Portugal, but in the most recent day of sequencing, which was two weeks ago, all eight cases sequenced were BA.2. 7/9
Spain, like Portugal, has poor genetic surveillance, but is seeing a similarly steep rise in BA.2.

Small sample size makes this a pretty unreliable estimate, however. 8/9
Most of the other countries whose graphs I posted in a previous BA.2 update have seen little change. Not much has changed in Sweden, but I'll include it here since it has among the highest level of BA.2 among countries with decent sequencing. 9/9
I was rushed when putting together this thread and made a mistake in the number of BA.2 cases recorded in Indiana. There have actually been 12 BA.2 sequences in the most recent 8 days of sequencing, not 6. This gives Indiana the highest percentage of BA.2 of any US state.

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More from @LongDesertTrain

Mar 26
So it's clear that BA.3.2 preferentially infects children, something we have never seen before in a SARS-CoV-2 variant.

Why?

The question's baffled me, but after a suggestion from Darren Martin, I think I have an explanation that makes sense.
1/16
I've tried to make sense of BA.3.2's penchant for kids by considering its unique spike: more compact, more closed, & more antibody-evasive than any other variant.

But I think another feature of BA.3.2 is responsible: its wholesale deletion of ORF7a, ORF7b, & ORF8 (∆ORF78).
2/
∆ORF78 is rare but not unheard of; it was in several late XBB variants (GW.5.1.1, FW.1.1, GE.1.2, etc) & a few branches of other variants. I've long thought these late XBB had an advantage in some population subsector, but I didn't suspect kids.
3/
Read 18 tweets
Mar 24
You have to wonder for how long we will continue seeing infections from 2020 continue to show up (in absurdly high quantities) in wastewater.
1/16
I suspect that the number of people continuously infected since 2020 or 2021 is much larger than we realize. It's impossible to prove, but there are case studies where a chronically infected person gets infected by a new variant, which drives out the original virus...
2/16
...which consequently leaves no trace that the person was chronically infected before the super-infecting variant—took over.

Why then are some Cryptic WW variants resistant to being outcompeted by newer variants?
3/16
Read 16 tweets
Mar 22
While the final outcome for BA.3.2 is uncertain, its unique characteristics—extensively remodeled spike NTD & SD1/SD2, novel S2 muts, & total deletion of ORF7a/7b/8—make it the best candidate for co-dominance we've seen, which could mark a new era in SARS-2 evolution. 1/
Until now, the broad pattern of SARS-2 evolution has been:

1) Emergence of a saltation variant originating in a chronic infection

2) Rapid growth/global dominance & a variant-driven wave of infection—especially if it emerges in late fall/winter (BA.1, XBB.1.5, JN.1). 2/
3) Stepwise evolution over the next few months/years, usually without driving major waves (the JN.1-descended KP.3.1.1 being a notable exception).

4) Repeat

3/
Read 34 tweets
Dec 29, 2025
Very proud to be a co-author on this comprehensive preprint on the novel, growing saltation lineage BA.3.2, together with @Tuliodna, Darren Martin, Dikeledi Kekana, and lead author @graemedor. 1/9
I would normally write a summary 🧵 of the BA.3.2 mutational analysis here, but as much of my contribution parallels my previous BA.3.2 threads I'll just link to those here, w/brief descriptions of each.

This is my first, big-picture BA.3.2 🧵. 2/9
Short thread from June when the first travel BA.3.2 sequences showed up. I think my prediction from back then has pretty much been borne out. 3/9
Read 9 tweets
Dec 24, 2025
BA.3.2 emerged in Nov 2024 after ~3 years of intrahost evolution with >50 new spike AA muts, but since then, it's changed very little. Could the drug molnupiravir (MOV) galvanize BA.3.2 into pursuing new evolutionary paths? A new 89-mut MOV BA.3.2 seq suggests it could. 1/11 Image
Background on MOV: It's a mutagenic drug. Its purpose is to cause so many mutations that the virus becomes unviable & is cleared. But we've long known this often does not happen. Instead, the virus persists in highly mutated form & can be transmitted. 2/
I was an author on a paper published in @Nature that conclusively showed not only that MOV has created highly mutated, persistent viruses, but that these viruses have transmitted numerous times. See 🧵 below by lead author @theosanderson. 3/
Read 11 tweets
Dec 22, 2025
The most valuable viral research tools—@nextstrain & CovSpectrum—are being destroyed, not only blocked from new data but now forbidden from even sharing info from the PAST. Why?

Because GISAID is run dictatorially by a con man, paranoid egomaniac, & liar named Peter Bogner. 1/
I use CovSpectrum & Nextstrain every day—& I'm not the only one. Every Covid thread I've ever posted here has relied partly on CovSpectrum & Nextstrain for information & visuals. These vital tools have now been stolen from us by a world-class grifter. 2/ thinkglobalhealth.org/article/to-fin…Image
For years scientists knew something was very, very wrong with GISAID, but the breakout story (from which much of this 🧵is based) came 2 years ago in @ScienceMagazine from @sciencecohen & Martin Enserik. 3/
science.org/content/articl…
Read 22 tweets

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