Post #1332: More transmissible than the Delta variant?

Posted on November 26, 2021

You read a lot of hype every time a new variant of COVID-19 is discovered.

Stories on COVID-19 variants are a nearly-ideal source of click-bait.  They combine a high fear content, a broad target audience, and a near-infinite repeatability.  The virus has an almost unlimited ability to spawn variants, and each one has the potential to do any number of scary things (avoid your immune system, avoid current vaccines, spread rapidly, and so on).  Report on some scientist talking about that potential, and you’re done.  Eyeballs captured.

These days, stories on COVID-19 variants rank right up there with school bus crashes and mass-murder events involving children as the lowest common denominator of fear-based journalism.

And yet … well, yeah, Delta.

And Alpha.  Everybody forgets about Alpha (a.k.a. the British variant) because it got its butt kicked so swiftly by vaccination.  And Delta.  But in its day, it was a threat to be reckoned with.  If the virus had stopped at Alpha, we’d be done by now.

Press reporting on COVID-19 variants is one of those ugly situations where almost all the information is irrelevant.  But some isn’t.  How do you filter out the signal from the noise?

Short answer:  Transmissibility, a.k.a. “R-nought”, a measure of how readiliy the mutated virus can spread.  That’s the minimum screen for filtering out the noise from the potentially relevant.

Why?  The way that a new variant takes over is by “out-competing” its rivals.  For that, it doesn’t matter how deadly it is, or how sick it makes you.  All that matters is that it can spread more effectively.  If it can, it will eventually become the dominant strain.  If it can’t, it won’t.

The reason the Alpha (British) strain took over from the original (Wuhan or native) strain was that it was more transmissible.  The reason Delta took over from Alpha was the same.

Like so, from this seemingly-plausible reference, where R0 = “R-nought”:

Professor Cheng said last year's Wuhan strain had an R0 value of around 2.5, the Alpha strain was about 3.75 and the Delta strain was about 5.

That means if we were living life like we were in 2019, one person with the Delta strain would likely infect five other people, compared to just 2.5 last year.

As a result, until I see those words — “more transmissible” — I just ignore it.  Because anything that’s not more transmissible than Delta is not going to displace Delta as the dominant strain.  No matter what else it does.

As a result, I rarely talk about new variants.  The last time I talked about a new variant was back on June 15 2021.  (Post #1160: COVID-19 Delta variant bodes for a 5th U.S. COVID-19 wave. )

This post puts a marker down for the latest variant out of South Africa, currently termed B.1.1.529.  This one ticks all my boxes for indicators of being  “more transmissible” than the Delta variant.  Per popular press reporting, a) it’s spreading rapidly in South Africa, b) the South Africans have ruled out mere chance (e.g., a few super-spreader clusters), c) it’s rapidly displacing Delta as the dominant strain, where it exists, d) it’s spreading rapidly in other countries where it has already spread to, and e) other countries (Israel, Great Britain) are already taking steps to try to contain it or slow its spread.

Anything else you may read about it seems to be speculation, at this point. It may evade current vaccines, evade the immune system, blah blah blah.  Sure, it may.  And it may not.  Nobody knows yet.

There isn’t even an estimate of it’s native transmissibility (its “R-nought”) yet.  So nobody has even done the analysis to take a guess as to where it ranks relative to prior strains.

We’re still at that stage where the reporting is confused, and the likely future of this new strain is uncertain.  All I can say is that after reading through the reporting this morning, this one seems to be worth watching.  Despite the lack of any hard estimate of transmissibility.  Despite the small number of cases so far.  As with the Delta variant, this one — likely to be given the Greek letter omicron as its designation — is worth keeping your eye on.