[conspire] When to get a covid test, brains, and a weird case, and a cardiology vs. immunology joke

[Rick Moen]

Quoting Ivan Sergio Borgonovo (mail at webthatworks.it):

> So the only delta you can achieve with "heard immunity" is obtained
> by not over stressing the health care system and it is due to the
> fact you can cure better people not by the fact that by magic once
> more people get infected and some of them are lucky enough to pass
> it nearly unaffected the virus will start to be less deadly to the
> remaining ones.

I may not have been fully clear.  The presence of people with immunity
to the pathogen, whether gained through prior exposure to the disease or
vaccination or (as Deirdre suggests) designer antibodies functions in
damping down disease spread the way moderator rods do in a nuclear
reactor, stopping the nuclear chain reaction.

E.g., if a person with measles, during the time he/she is contagious,
exposes 18 people with no immunity, then that one person causes the 
diseased population to expand 18-fold, before ceasing to him/herself be
infectious.  If, on the other hand, 17 out of those 18 people (94% of
them) have had the MMR vaccine, then the original person's infectious
phase ends with _one_ new case, and the rate of infection will not have
risen.  If 95%+ of the population have MMR, then the infection rate will
over time fall and eventually sputter out, ceasing to infect others.

The term 'herd' (not heard) immunity is a metaphor from herds of
animals, where a disease doesn't spread out of control among them if a
high enough percentage of the herd (relative to the disease's
infectiousness) have enough immune system resistance.  With measles, if
95% of a 'herd' of humans have antibodies to measles (preferably from
having the MMR vaccine rather than having gone through measles), or in
the jargon are seroprevalent (the right antibodies are prevalent in the
person's blood serum), then one member of the 'herd' getting the measles
cannot cause a wildfire infection among the rest.

Serendipitously, _Washington Post_ graphics reporter Harry Stevens has
just now published an excellent piece detailing how this concept applies
to the USA population for COVID-19 infections:
https://www.washingtonpost.com/graphics/2020/health/coronavirus-herd-immunity-simulation-vaccine/

As Stevens points out, even the US cities and states that have had the
worst outbreaks are nowhere near the herd immunity threshold even using
the most wildly optimistic assumptions about COVID-19 infectiousness,
and we know this because seroprevalance remains far too low.

Stevens's article offers the reader a calculation widget to run the
numbers, where you plug in three numbers, the first of which is given:
(a) total population (328 million for the current USA), (b) COVID-19's
herd immunity threshold percentage (another way of expressing R naught,
as I mentioned upthread), and (c) the fatality rate from being infected.

You can twiddle the two variable numbers, and observe how many COVID-19
cases would result in achieving herd immunity, and how many patients
would be killed.  (And, don't forget, despite a great deal of
ideologically motivated resistance to the realisation from people like
most of the folks on Ruben's 'docs' mailing list, there are good reasons
to think that many infectees who recover from the infection without
dying suffer a variety of long-term harms, possibly permanent harm.)

Anyway, playing with Stevens's widget is enlightening about what
'achieving herd immunity' (without a good vaccine or other measures such
as designer antibodies) would necessitate:  It's pretty gruesome, with
any credible value for the two plug-in numbers.


> Again if you project the death rate of region like Bergamo worldwide
> you're talking about millions of causalities.

Without a doubt.  Many, many, many millions.


> So "let it be" doesn't work and heard immunity without a vaccine is
> bullshit.

Well, herd immunity 'works' by definition.  You end up having
consequences (as Stevens's small model shows).  The UK and Sweden based
government policy on drifting towards laissez-faire allowing the
infection to spread, but then blanched as the staggering cost in health
and lives became apparent, and decided it was a terrible idea after all.

The right-wing echo-chamber in the USA nonetheless pushes the idea, to
this day, having pretty much literally become a death-cult (though they
always pitch it as 'We don't _want_ this; it's just the only
possibility'.  Faux News nutcase Laura Ingraham mouths _exactly_ the
'docs' mailing list mantra.  Note in particular the first sentence:

   Herd and T-cell immunity focus is only practical way forward.  
   Simple test for T-cell immunity would be a confidence booster. 
   Death rate a fraction of April peak.  Lockdowns are purely 
   political at this point—and will cause incalculable suffering.

https://twitter.com/IngrahamAngle/status/1287031537335259137