Cold Covid - part the eighth

A paper in "Nature", dated yesterday offers this support for Constant Power^©

Trevor Bedford, an evolutionary biologist at the Fred Hutchinson, says the virus must balance its ability to replicate to high levels in people's airways with the need to keep them healthy enough to infect new hosts. "The virus doesn't want to put someone in bed and make them sick enough that they're not encountering a number of other people"

Or die fast. Of course. SARS and MERS made that mistake. As if they could have figured it out.

On the other hand, is this:

"There's this assumption that something more transmissible becomes less virulent. I don't think that's the position we should take," says Balloux. Variants including Alpha, Beta and Delta have been linked to heightened rates of hospitalization and death — potentially because they grow to such high levels in people's airways. The assertion that viruses evolve to become milder "is a bit of a myth", says Rambaut. "The reality is far more complex."
[my emphasis]

Yet, it's clear from the graphs in the report that Delta, through its transmissibility, dominated both Covid-α and Covid-β and has been less virulent, at least in the USofA to date.

If you read up the Michigan page (which had the greatest Alpha peak) of the NYT Covid data, it's unequivocal that Covid-α deaths (trailing the case peak by weeks as always) trailed ancestral Covid-19 by about half (127 vs. 70 7-day average peak). Hospitalizations, certainly, followed cases above ancestral Covid-19 (proportionately) by a tad; that's to be expected. Yet, the claimed greater transmissibility would lead one to believe that both cases and hospitalizations would be even greater. There's nothing in the data to support the notion that Covid-α was/is more virulent. Recall that Covid-α happened before widespread vaccination.

At the National level, an Alpha peak barely registers in the case and hospitalization graphs, and doesn't register at all in the deaths graph. Delta trails ancestral in all the graphs. So far.

At least in the USofA, Beta barely registered. Referencing the "Nature" graphs, if you look close and squint, you can see a teeny sliver of Beta at about the time of the Alpha peak.

An earlier "Nature" report had this

As the more-transmissible Delta variant spreads, Beta is now fading in many places where it was once dominant, including South Africa and Qatar.

Which is just what one might expect if Darwin and Constant Power^© hold. I will concede that both may fail at the margins; that is, a minuscule increase in virulence may appear in a variant with little-to-no difference in transmissibility compared to ancestors. A significant increase in virulence appears impossible to correlate to a significant increase in transmissibility. You can't infect (well, too much) if you can't move and then you just die. SARS and MERS demonstrated that principle.

As to whether Covid-δ is more virulent? At the national level, the three graphs show that ancestral and Covid-δ have proportionately (compared to case level) the same level of hospitalization and death. What Covid-δ is doing differently, so far (a bit), is demonstrating a double peak. Thank you Red States and Counties. Referencing the Michigan page, the Hot Spot map correlates vewy, vewy closely to the Vaccination map; just inversely. To see at the most granular level currently to hand: pull up the Montana page and note the southeast corner of the state. The third column of counties from the eastern border has Rosebud (I can't make this up!), Big Horn, and Treasure counties. Compare the Hot Spot and Vaccination maps; lo and behold Treasure is a pit of Covid and failing vaccination surrounded by not so much. QED. Of course, Tester voted (or will, depending) against the employer vaccine mandate. I guess even he doesn't mind a few more body bags.

I'll go out on a limb (yet again) and offer that Covid-ο is the best defense against Covid-δ just as it was against Covid-β. Which is not to say that Covid will always mutate to more transmission and less virulence (some whackadoodles have gone that route), but that there is A) a limit to the virulence that a virus can impose before it implodes, B) a significantly more virulent virus must necessarily be more localized as it consumes hosts faster than they can spread the virus, and C) a competition between transmissibility and virulence will go the former, at least on the data.