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Re: [Phys-L] It's this simple ... isn't it?

To answer the question posed by the subject line:
Yes. Pretty much.

On 4/6/20 2:45 PM, Albert J. Mallinckrodt wrote:

In the absence of a vaccine, there are only two ways to end the
explosive and relentless exponential increase in infections,
hospitalizations, and deaths and see a "peak" of any kind in any
given local outbreak of COVID-19:

1) Institute sufficient social distancing to bring the basic
reproduction number, R, under 1, in which case we get reversed or
negative growth


2) wait until herd immunity kicks in because virtually EVERYBODY has
been infected.

That's all true as stated.

The word "wait" is doing a lot of work in the second scenario. Much
depends on the timing.

In the first case you get 1) a peak in daily new infections almost
immediately, 2) a peak in daily deaths about 20 days later, and 3) a
final death toll that is something like 20 to 100 times the number of
deaths on the peak day.


In the second case, you get 1) a peak in new infections much later
(maybe 10 to 15 doubling times down the road from the first 10
deaths), 2) a collapsed hospital system, and 3) a total death toll of
something like 2 to 10% of the entire local population (based on both
the mortality of the disease and on the collateral damage from the
collapse of the hospital system.)


Collapse is not a binary thing. There is a continuum of public-health
measures that could be taken, and a continuum of outcomes. One could
reasonably try to model how bad the collapse will be, in various scenarios,
and make policy decisions accordingly.

Forsooth, the measures that weaken the collapse are the same as the
ones that at some point imperceptibly convert scenario (2) into
scenario (1).

So the choice is ours. Are we going to wear our masks and stay the
f**k at home ... or not?

Depends on what you mean by "we", Kemosabe.
-- Personally I haven't gone out in public in over a month, except
for a couple trips to the grocery store, and I wear a mask for that.
-- As for the big epidemiological "WE", I keep hoping, but I have a
hard time imagining a scenario where R₀ goes below unity before
virtually the entire herd is infected. Look where we are already:
the number of /actual/ cases is enormous. It exceeds the "confirmed"
cases by at least an order of magnitude, due to scandalously abysmal
testing. And even at this late date, there are still many states
where hunker-down orders do not exist at all, or are so lax as to be
ineffective. Furthermore, even if President Kenny Vaughn wanted to
call for a nationwide lockdown, or even a mask-wearing program, the
talk radio guys wouldn't let him. They are quite deeply dug in behind
the "it's all a hoax" storyline. They seem to be waging germ warfare
against their own supporters. I take no joy in that, not even a tiny
bit, for multiple reasons, moral and practical. The most obvious
practical reason is that they're going to cause unimaginable amounts
of collateral damage to innocent bystanders.

That's always the problem with biological warfare. It's nearly
impossible to aim the weapons.

MINOR points:

a) One tangential point I might add: There *could* have been outcomes
other than the two outlined above, but that horse left the barn some
weeks ago. Comprehensive testing, contact tracing, vigorous but selective
isolation of patients who are contagious, et cetera. South Korea.
Iceland. Singapore. Other places managed to do it.

b) There are multiple IHME scenarios, but the one that is being widely
quoted is predicated on the assumption that starting today we do everything
right, which seems rather far out in the rosiest corner of scenario space.
So far we (in the US) haven't done anything right.

c) One could perhaps elaborate the model slightly, if one hypothesizes that
some jurisdictions wall themselves off and stop the infection "within the
dome" while hell fires rage around them. This doesn't seem particularly
likely, but I can't completely rule it out. The large-ish places that
seem like plausible candidates (Hawaii, Key West) are so dependent on
tourism that they're not too eager to raise the drawbridge and keep it
up for an extended time. Maybe Supai, Arizona (population 200, no roads
in or out).

This might change the outcome locally, but changes virtually nothing about
the medical, economic, sociological, and political predictions of the basic
simple model.