
Exponential Growth and Covid-19 [video] - tomerbd
https://www.youtube.com/watch?v=Kas0tIxDvrg
======
lhl
I've been tracking the coronavirus news for the past few weeks and have found
[https://www.reddit.com/r/covid19](https://www.reddit.com/r/covid19) to be
good for tracking the latest scientific/medical publications, and
[https://www.reddit.com/r/coronavirus](https://www.reddit.com/r/coronavirus)
for general news.

For transmission rates, this team is updating their modeling results often:
[https://cmmid.github.io/topics/covid19/current-patterns-
tran...](https://cmmid.github.io/topics/covid19/current-patterns-
transmission/global-time-varying-transmission.html)

On twitter, @datagraver is publishing some of the most interesting
visualization/graphs:
[https://twitter.com/Datagraver](https://twitter.com/Datagraver)

I've found this via mrb (@zorinaq) who's been tracking the covid19 spread:
[https://twitter.com/zorinaq/status/1235850389020270595](https://twitter.com/zorinaq/status/1235850389020270595)

~~~
haunter
Both of those subs are incredibly tinfoily and panicky. Honestly reddit is the
worst. And BI is right that they are doing the same as always, just consiparcy
things

[https://www.businessinsider.com/coronavirus-reddit-social-
pl...](https://www.businessinsider.com/coronavirus-reddit-social-platforms-
spread-misinformation-who-cdc-2020-3)

Also you might as well rename /r/Coronavirus/ to /r/politics2 aka fucktrump.
It's the same thing over and over again

~~~
jacobolus
Edit: here’s a Lancet Editorial “COVID-19: too little, too late?”
[https://www.thelancet.com/journals/lancet/article/PIIS0140-6...](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736\(20\)30522-5/fulltext)

* * *

Seattle is about 2 weeks behind Lombardy. The Bay Area maybe 3 weeks behind.
Everywhere in the US is going to be in that situation in 2 months at most,
unless something very dramatic changes ASAP.

The kinds of measures being taken in the US are grossly inadequate for this
challenge: leaders and some media outlets continue to downplay risks,
residents continue to blithely go about their everyday lives, large gatherings
like church meetings and sporting events continue as usual, the CDC/FDA is
still blocking sufficient testing around the country, hospitals and medical
workers are not being sufficiently trained and prepared, and the supply of
personal protective gear and ICU beds is not going to suffice.

We have squandered 4–6 weeks of preparation for this crisis, and hundreds of
thousands of people in the US may die as a result, with others experiencing
permanent lung damage.

China has shown that this virus can be managed if the number of patients stays
low enough that infections are discovered early and patients are treated
aggressively with antivirals, supplemental oxygen as soon as blood oxygen
starts to drop, mechanical ventilators for severe cases, etc. People’s immune
systems generally do fight this virus off if we can keep them breathing for
long enough. But that depends on having enough hospital capacity.

If everyone stays complacent and continues to mingle until there are hundreds
of local deaths in each area it’s going to be a disaster.

Edit 2: To everyone here: If you have what seems like a minor cold, even if
you are a young adult, please stay away from people and don’t spread it. What
is 2 weeks of minor cough and sore throat for you might become severe
pneumonia requiring hospitalization for your parent or neighbor or coworker.
If anyone in the family gets a minor cold, please keep your kids out of
school. Etc.

~~~
war1025
> If anyone in the family gets a minor cold, please keep your kids out of
> school. Etc.

Unfortunately this is effectively "let them eat cake" for many people.

Keeping kids out of school means not going to work. Not going to work means
not having money to pay the bills, and very possibly losing your job.

In China, where the state has basically total control, things like this can be
done. In the US, it's going to be a tough sell for an awful lot of people.

~~~
jacobolus
I would feel a lot more comfortable if the USA had a testing setup like South
Korea (where they have performed something like 500 times as many tests per
capita as the USA, and then done aggressive isolation and contact tracing for
positive cases).

If it were up to me the federal government and state and local governments
would be closing schools, closing nursing homes to visitors, canceling church
services and sporting events, figuring out how to make transportation less
risky, closing restaurants and bars to customers and drafting those workers to
make deliverable prepared meals instead, recruiting childless people aged
15–40 into temporary (paid) public service jobs, doing everything possible to
guarantee sufficient supply of protective equipment, taking every roadblock
out from researching antiviral drugs for treating positive cases, etc.

Governments should be figuring out how to guarantee anyone with untested minor
colds to stay home from work without losing pay until they can be tested;
figuring out how to temporarily relieve rent, loan payments, and taxes for
people quarantined or with jobs in temporarily affected industries; preparing
to distribute food, medicine, and other items to patients in quarantine or
isolated at home, and so on.

With a robust public response it should be possible to dramatically slow this
virus without completely collapsing the economy. The fallout (not just
illness/death but also economic impact) from all the cases hitting at once
within a few weeks is going to be much more worse.

I’m not sure exactly what the best responses would be, I’m just spitballing
here. But it seems to me we should have been thinking and talking about
possible extreme measures for the past 6 weeks instead of collectively
twiddling our thumbs and going on with our ordinary lives.

------
nabla9
In simplest possible SIR model that takes into account the growing recovered
and immune, (1 − 1/R0) of the population gets infected. R0 is the reproduction
rate.

    
    
        R0 | % of population
        ----------------
        2.5  60% 
        2.0  50% 
        1.5  30%
    

The effective reproduction rate decreases when people take precautions. There
is no reason to assume it's constant or same in different countries and
cultures.

~~~
microcolonel
> _The effective reproduction rate decreases when people take precautions._

In looking at the outbreak gripping Italy, it seems like hard quarantine is
the most basic precaution, and perhaps we should be taking it _before_ the
first hundreds of people die in each of our countries.

~~~
vanniv
Italy's quarantine will probably kill many more people than the virus ever
could

~~~
microcolonel
What's your reasoning on that? I really want to know, since on the face it
seems like an absolutely outrageous, borderline random conclusion to draw.

~~~
vanniv
It has been 2 days. Now, all businesses except grocers are closed, and grocers
are mostly out of food.

Roads are closed.

People are going to be very, very hungry very, very soon.

Hunger will create desperation, which will create violence, which will quickly
dwarf the few thousands of people that covid will kill

------
melling
The video says that it's really a logistic curve. Which is also the activation
function (sigmoid) in a few machine learning articles that I've been reading.

[https://en.wikipedia.org/wiki/Sigmoid_function](https://en.wikipedia.org/wiki/Sigmoid_function)

[https://en.wikipedia.org/wiki/Logistic_function](https://en.wikipedia.org/wiki/Logistic_function)

Can anyone recommend anything to read to add more clarity?

Why does this appear in deep learning too?

~~~
bno1
In machine learning it's used as an activation function. Activation functions
are used to add non-linearity to the model. I think sigmoid functions are
inspired from neurons, but I'm not sure exactly how. Nowadays, ReLU
activations are used more often than sigmoidals because they are quicker to
compute.

~~~
cmarschner
ReLu are mainly used because in practice they show better results than
sigmoids in many areas. The fact that they are also faster to compute is just
a nice side effect.

------
melling
China looks like its growth has flatlined, while the rest of the world is
moving along an exponential curve.

[https://www.arcgis.com/apps/opsdashboard/index.html#/bda7594...](https://www.arcgis.com/apps/opsdashboard/index.html#/bda7594740fd40299423467b48e9ecf6)

Also, notice that 57k out of 81k have recovered.

~~~
cklaus
China has only flatlined because extremely aggressive social distancing. I
don't see that in the US occurring.

~~~
maxerickson
Why? We're a bunch of paranoid lunatics, primed to avoid each other.

~~~
abootstrapper
False. We’re a bunch of mostly self centered individualist who don’t like
being told what to do and don’t trust facts, ideas, opinions, or people that
contradict our preconceived notions.

~~~
maxerickson
What exactly do you think "paranoid" and "lunatic" mean?

~~~
TeMPOraL
Problem is: when what authorities tell you is to distance yourself for others,
a paranoid lunatic will obviously smell a conspiracy and do the exact
opposite.

------
cklaus
American Hospital Association "Best Guess Epidemiology" for #codiv19 over next
2 months:

96,000,000 infections

4,800,000 hospitalizations

1,900,000 ICU admissions

480,000 deaths

vs flu in 2019:

35,500,000 infections

490,600 hospitalizations

49,000 ICU admissions

34,200 deaths

~~~
abootstrapper
Source link?

~~~
cklaus
Source:

[https://www.businessinsider.com/presentation-us-hospitals-
pr...](https://www.businessinsider.com/presentation-us-hospitals-preparing-
for-millions-of-hospitalizations-2020-3)

------
yters
Seems to have a much lower hospitalized mortality rate than 2017 flu
[https://www.google.com/amp/s/www.livescience.com/amp/new-
cor...](https://www.google.com/amp/s/www.livescience.com/amp/new-coronavirus-
compare-with-flu.html)

~~~
shawabawa3
From (probably slightly misremembered) stats I've seen, it has approximately
40x the hospitalisation rate, but only 10x the death rate of flu

So yes, lower hospitalised mortality rate but only because so many more people
are hospitalised

~~~
yters
Do we have an accurate count of cases? For example if most cases are
determined based on hospitalization, then the hospitalized death rate is the
same as the estimated actual death rate.

I haven't been able to find studies on the hospitalization rate to know.

------
FranceBacce
If anyone wants to dig into the math, this is a non linear recurrence
relation, with an external dependency, that is n_d+1 = f(a,n_d) n^(d+1)

bad news: How this behaves will depend a lot on a (containment measures
etc...)

good news: If we can make a grow faster than an exponential, we can win

------
sgt101
Does anyone have numbers for testing? I'd like to know how many tests are
being done in each territory?

------
JetBen
As an anxious person, I actually found it calming to watch the math of it all.

------
forkexec
Sigh. It's not exponential growth, it's best modeled by a differential
equation. Like population, the rate of growth is proportional to the amount
present up to the current carrying capacity (that varies widely in the real
world and with time).

~~~
CPUstring
That is explained in the video

------
XiZhao
VCs love this virus!

------
tic_tac
There are two extreme paths we can take. The first is that we do nothing, the
other is that we completely lock down our society like China.

While the first option would be unwise, the second would also be unwise.

A complete shutdown for a disease as virulent as Covid-19 will just suppress
the virus for the duration of the shutdown. Ignoring the extreme difficulty
and impracticality of shutting society down for a moment, recognize that the
moment the shutdown ends, the virus will probably reappear and continue to
spread.

What then? Another complete shutdown? When does it end?

No, the right solution is a distributed solution in which affected companies
and communities deal with the virus, imposing gradual restrictions on
gatherings, work, schooling etc in an organic way. Which is exactly what is
happening in the US right now.

The point of all this is, what more can the US government do than it is
already doing? Send the military in to shut down the highways? Hold scientists
at gunpoint until they produce a vaccine?

Many (Media, Democrats) are trying to leverage this to their political
advantage, but aside from small changes in approach, what exactly do they want
the government to do differently?

~~~
qqqwerty
> Many (Media, Democrats) are trying to leverage this to their political
> advantage

To date, most of the complaints about the current administrations' handling of
COVID-19 have been about the cuts to the CDC, the history of Pence and
Redfield regarding HIV, and other fact based arguments and criticisms. It is
entirely possible that none of these factors had or will have a substantive
impact on the spread of COVID-19. But they are still valid criticisms none the
less.

In contrast, take Trump's response to the Ebola crisis[1], which was a
remarkable example of fear-mongering and politiking in the face of a potential
crisis.

[1][https://www.vox.com/2020/2/26/21154253/trump-ebola-tweets-
co...](https://www.vox.com/2020/2/26/21154253/trump-ebola-tweets-coronavirus)

------
ccarpenterg
What about Polynomial growth:
[https://oeis.org/wiki/Growth_of_sequences#Polynomial](https://oeis.org/wiki/Growth_of_sequences#Polynomial)

------
tunesmith
I figure there's some kind of "true" fatality rate that just answers the
question of "If you catch the virus, you have this (age-adjusted) chance of
dying". It seems like we'll asymptotically reach that "true" rate once testing
is extremely common and liberal (to have confidence you are identifying all
cases). Some countries are reaching that testing rate. Then your upper and
lower bounds for that death rate are "deaths / deaths + recoveries" and
"deaths / confirmed cases", respectively, and they should converge as "active
cases" decrease over time (as they either recover or die). You can use that
"band" (between the upper and lower bounds) to judge other countries and
determine whether they are testing enough - if they are above that "band",
they are clearly not testing enough.

~~~
swsieber
Are we talking with or without ventilator/hospital support?

~~~
tunesmith
Yeah, that's a good point. Fatality increases as treatment options decrease.
Treatment options can decrease whether it's a less advanced country, or a more
advanced country that just gets overwhelmed due to poorer containment than
other advanced countries.

