To herd or not to herd  
At the start of the infection, the team from Imperial College,
London  outlined a supression strategy. It involved
community isolation to drive the first wave down close to
zero, followed by cycles of reopening and closing to keep in
the infection under control. A few countries have made
serious effort to execute this plan, China, South Korea and
New Zealand.

As shown in the graphs, The US has moved to reopen after
the infection has only stalled. Without a change in the level
of isolation and quarantine, this is expected to result in an
increase in infection.  


Whether by design or default, reopening without
test/trace/quarantine means we are headed towards herd
immunity.  It now looks like we can be more confident about
the number of infectious asymptomatic’s running around, so
we can evaluate our current situation with more confidence.
The only way to know if anyone has been infected but
asymptomatic is through an antibody test, and they have
only just become widely available. There are now 2 large
studies, one in New York with 3,000 people and one in
Spain with 7,000 people that find that the ratio of antibody
positive to new cases (Asymptomatic/Symptomatic) are
nearly identical at 10.15 +- 0.05 !
Sources: https://english.elpais.com/society/2020-05-
14/antibody-study-shows-just-5-of-spaniards-have-
contracted-the-coronavirus.html  and worldometer data for
new cases.





Here is a possible scenario – NOT a prediction !

The graph shows the model calculation in mid June, if
NOTHING CHANGES, or if we re-lockdown around June 1st.
Based on the first wave, it takes about 2 weeks for a change
in behavior to show up in the case count. The do nothing
scenario, is close to the “worst case” in the latest IHME
model, and takes us to cases and deaths that are about 2x
the worst case NY experience. IHME says that by Aug 1, we
could be out of ICU beds. For Austin (Travis) county,
something like half the hospital beds would be Covid, which
is presumably why temporary hospital capacity is being
considered.

The other aspect of do nothing is that by October we are
close to 70% exposure, so well on our way to herd immunity.
At what cost - the best (worst?) estimate of getting to herd
immunity

“So it would not be unreasonable to say based on what I just
shared with you with 100,000 deaths for 5% of the
population infected, that somewhere between 800,000 and
1.6 million people could easily die from this over the course
of the next 12 to 18 months if we don’t have a successful
vaccine.”
https://www.bluezones.com/…/covid-19-straight-answers-
from…/

AND this assumes a functioning health care system – could
be worse.
The original Imperial College model for a controlled open and isolate strategy to control
the infection. As a contrast I have illustrated the US approach in early May.
Base on data available in the end of May,a model prediction for the future trend if the level of
isolation/ test and quarantine in TX is maintained. It suggests that  IF NOTHING CHANGES, we
will approach NY levels of infection by late August.