[ExI] riots, was: RE: Is a copy of you really you?

[Rafal Smigrodzki]

On Tue, Jun 2, 2020 at 1:46 PM Keith Henson via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

>
> I hope what I posted above is wrong and you are right.  What do you
> think is wrong with my analysis?  The range I have seen on herd
> immunity is 60 to 80% so I used 70% for analysis.  If you have a
> better number for me to use, what is it?
>
> The antibody testing results for the two California locations are
> centered around 4%.  I am aware there is some uncertainty in this
> number, but if herd immunity takes 70%, then 70/4 is around a factor
> of ~17.  That indicates to me that the pandemic has quite a way to go
> at least in California.
>

### The infectivity of Covid-19 is relatively low, much less than initially
suspected. Observations of household transmission show that as few as 15%
but perhaps as many as 50% of household members become infected from the
index case. Household transmission means 7 days in close proximity to the
index case, indoors, for many hours a day, at close quarters, so this level
of transmission implies low infectivity in general.

There is a relationship between R0 and the herd immunity level - the higher
R0 the higher the percentage needed for herd immunity. Downward revision of
R0 based on household transmission implies that herd immunity should be
achieved at lower levels. The exact percentage will of course vary in
different locations - it will be much higher in NY city than in suburban CA
- but it will be much lower than the initial estimate of 80%. We know that
the seasonal influenza infects usually  less than 15 - 25% of the
population per year, and there are good reasons to expect C-19 will be
similar or less. We know that there is a substantial prevalence of immunity
to C-19 in the population at baseline, due to cross-reactivity and
cross-immunity between C-19 and the coronaviruses responsible for the
common cold. This is similar to influenza, where some cross-immunity exists
between strains active in different years.

This means we are not 1/17th of the way to herd immunity. Most likely we
are at least 1/3 there as a country, maybe even 2/3, and NY is almost at
herd immunity level now (see their curve of new cases).

Of course, the Iran second wave is worrisome. On the other hand, Spain,
Germany, Sweden and most other countries seem to be doing well, lockdown or
not.

It's also useful to remember that between 40 and 80% of C-19 deaths occur
in nursing homes. If you are not in a nursing home, your risk is much
lower, even if elderly.

Rafal
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