
Covid-19 twice as contagious as previously thought – CDC study - deegles
https://thinkpol.ca/2020/04/08/covid-19-twice-contagious-previously-thought/
======
ggm
I will repeat a question I would love an epidemiologist to reply to: Where is
the random background testing? Not testing "I feel unwell" presentations at
random, truly going into the field and testing the wider population at random,
healthy (believed) or not?

You cannot model the IFR accurately from skewed samples and it feels like we
aren't even doing skewed sampling.

~~~
XFrequentist
Epidemiologist here: you're right.

Testing resources are in short supply, so testing is being performed to guide
clinical decisions (ie sick people) rather than public health/science (ie
random sample).

The handful of serosurveys that have been performed have been quite valuable,
but there aren't nearly enough.

Hopefully this changes as testing capacity ramps up.

~~~
t2riRXawYxLGGYb
Soooo....

\- SARS started out with a similar <4% estimated fatality rate and was then
revised upwards to anywhere from 9-15% later.

\- COVID-19 is caused by a different strain of the same virus as SARS.

\- The CFR of SARS and COVID-19 appear to be very similar, and more notably,
appeared by be very similar when we had around 8,000 infections which is where
SARS ended. (Similar meaning the CFR hovers between 4% and 20% of closed
cases.)

 _How are we so sure that this is any less deadly than SARS?_

The above suggests to me one of the two is likely to be true:

1\. There could have been many more undetected cases of SARS than we knew
about, indicting an IFR much lower than it's recorded CFR.

2\. COVID-19 could actually end up having an IFR that is similar to SARS
(~10%).

But of course, I am no epidemiologist, so I assume there's a flaw in my logic.

Did I miss something, or is this pretty much the same disease as SARS but with
a higher R0?

~~~
capkutay
There's little to no data that backs up your guess.

Studies on COVID-19 estimate that the true IFR is somewhere between 0.1% to
0.39%...why? Because the more we test, the more we find asymptomatic and mild
cases. And we're yet to even do the type of serological testing that would
give us such a decisive sample. Yet we're ALREADY seeing data that suggests
that the IFR is lower than SARS and asymptomatic cases/transmission are
common. [0]

I never read anything about SARS being mild or asymptomatic in the majority of
patients...in fact it was the opposite. It was so severely symptomatic that
the virus killed itself with natural selection. If you had SARS-COV-11 and
exhibited high viral load, you were likely too sick to go spread it. The only
serological testing they did on SARS-COV-1 deemed asymptomatic cases to be
uncommon [1]. Quite the opposite of COVID-19.

0: [https://www.cebm.net/covid-19/global-covid-19-case-
fatality-...](https://www.cebm.net/covid-19/global-covid-19-case-fatality-
rates/)

1:
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3035549/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3035549/)

~~~
yread
I've posted this in an earlier thread but I don't think that low estimates
make sense. The virus killed 0.44% of total population of Bergamo

4500/1112187

[https://translate.google.com/translate?hl=en&sl=it&u=https:/...](https://translate.google.com/translate?hl=en&sl=it&u=https:/..).

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

EDIT: and there are harder hit communities: 400/40000
[https://www.ecodibergamo.it/stories/valle-brembana/il-
grido-...](https://www.ecodibergamo.it/stories/valle-brembana/il-grido-daiuto-
della-valle-brembana400-morti-su-40mila-abitanti2000_1348457_11/)

~~~
ed_balls
take the age bias into account. 45 for Bergamo and 29.6 for the world.

------
Animats
Stanford just tested 3200 people in Silicon Valley for antibodies at a drive-
through location.[1] There are similar group tests being run in LA and
Colorado. In a few days there should be more solid info on how many people
have had the disease without symptoms.

[1] [https://www.stanforddaily.com/2020/04/04/stanford-
researcher...](https://www.stanforddaily.com/2020/04/04/stanford-researchers-
test-3200-people-for-covid-19-antibodies/)

~~~
elliekelly
(As someone who knows next to nothing about medicine or microbiology) I’m
curious how they already know which antibodies to look for? Are antibodies
unique to each virus? Is it possible that some people have stumbled upon
antibody X at some point in their lives that maybe isn’t perfect for fighting
off this new coronavirus but still helps? Along the same lines, is it possible
some people have antibodies IgM and IgG from some other illness they’ve
encountered in their lives? Or is the presence of those antibodies conclusive
evidence that they’ve been infected with COVID-19?

~~~
refurb
They are looking for antibodies to the spike protein on COVID-19. So if a
person has those, then it's proof that they've been exposed to it.

Antibodies are unique for each virus, but there can be "cross-reactivity"
where an antibody for a different virus also binds to COVID-19.

Yes, it is possible that there are people out there who have antibodies that
bind to COVID-19, who have never been infected with it, but rather have an
antibody that cross-reacts with COVID-19. But it would be a very rare
occurrence.

So having COVID-19 antibodies isn't a _perfect_ was to tell if a person has
been exposed, but it's a _very good_ way to do it since antibodies is highly
correlated with exposure.

~~~
StandardFuture
Would antibodies that can attach to COVID-19 but were produced from a
different viral infection potentially make you immune to COVID-19?

~~~
toomanybeersies
That was the case with Smallpox and Cowpox, and the original vaccine.

~~~
elliekelly
Interesting! From the smallpox wikipedia page:

> The term vaccine derives from the Latin word for cow, reflecting the origins
> of smallpox vaccination.

------
tunesmith
I've seem people theorize about this before saying maybe it's good news
because that means it's less fatal than we thought and therefore maybe we're
closer to herd immunity. But I saw an epidemiologist talk about how an R0 of 2
meant you needed 50% of people to be immune for herd immunity, and an R0 of 3
meant you needed 66%. This would mean it'd need to be even higher - the
article says 82%. We're nowhere close to that now - even northern Italy,
they're estimating that maybe 10% have caught it.

~~~
fpgaminer
> because that means it's less fatal than we thought

Don't we already have solid numbers on the fatality rate because of the
Diamond Princess? A change in estimated R0 wouldn't affect that.

~~~
sooheon
Diamond princess is a non-stochastic sample, with all its attendant biases.

~~~
throwaway_pdp09
What does that mean?

~~~
kaybe
People on cruise ships are usually not a good sample of the general
population, for example, the mean age is quite high.

~~~
btilly
But it is also a sample with few in the sickest bracket, who are a
disproportionate fraction of deaths.

And the number of deaths is sufficiently small that it is consistent with a
wide range of death rates.

------
fspeech
The actual article that is both readable and informative
[https://wwwnc.cdc.gov/eid/article/26/7/20-0282_article](https://wwwnc.cdc.gov/eid/article/26/7/20-0282_article)

------
klenwell
Here's an early estimate graphed by the NY Times at the end of February
(scroll down a bit):

[https://www.nytimes.com/interactive/2020/world/asia/china-
co...](https://www.nytimes.com/interactive/2020/world/asia/china-coronavirus-
contain.html#virulence)

R0 estimated to be 2 - 4. Fatality rate: 0.1 - 3%.

This was the first information I saw that helped me understand why this was
more than just a bad flu. Still didn't truly understand it at that point, at
least the way I do now that we're experiencing the consequences of failing to
contain it.

~~~
snapetom
In pre-print on Feb 7, this paper initially estimated R0 to be somewhere
between 4.7 and 6.6. People dismissed it as being not possible. It was never
picked up by the MSM.

Now we're seeing from the both the real world and other studies that it's
pretty plausible.

~~~
jkhdigital
Yep, I read the preprint as soon as it was published and it scared me into
buying masks back in mid-February.

~~~
snapetom
Basic math, knowing population density, and then that paper was my "oh shit"
moment. Got some half respirators and 300 rolls of toilet paper over the next
week.

The toilet paper wasn't to prepare for a post-apocalyptic world. It was
because I knew that was the first thing other idiots would buy when news of
this thing hit your average Joe :)

~~~
DoofusOfDeath
Perhaps I'm misunderstanding your point, but it sounds like your bragging
about being the first person to start hoarding.

------
chickenpotpie
Can anyone explain how the virus is twice as infectious as we thought, but
we're consistently lowering our death projections everyday?

~~~
jariel
"but we're consistently lowering our death projections every day?"

'The first casualty if war is the Truth'.

Whatever the government tells you during a time of crisis is a form of
propaganda, 'for your own good' so to speak.

Even if individuals are intelligent, crowds are not.

Whatever they say is very calculated and controlled, as if to achieve a
specific outcome. So imagine a very cynical view of political messaging in
normal times, but now tilt that towards a more truly civic situation wherein
maybe it doesn't seem quite so cynical because, well, there is actually a
crisis.

The 'numbers' projected a few weeks ago will have been constrained by a) what
people could handle without panicking, b) what kind of numbers might get them
to actually behave properly, c) what will save every political leaders skin
(i.e. give bad news then everything after that seems like good news), d) how
much we can bend reality without hurting their own credibility by being
perceived as lying.

It's _extremely_ hard and politically risky to 'shut down a country' and get
millions of individual actors to 'buy-in' to behave as we want especially if
it means annoyance or personal hardship. Political leaders are used to acting
in a very populist way, and basically right now they are doing the extreme
opposite. Every day, politicians have to act against their best populist
instincts. It's hard to overstate what a sensitive time this is, it could go
sour very quickly.

So take everything with a grain of salt, knowing that whatever is being said
is calculated and 'all projections' are filtered somewhat. Ostensibly 'for our
own good'.

I think there are often more qualified numbers published out there, but you
have to go right to the source, if available.

Edit: the 'masks' PR and policy is probably the best example of that. In
reality, there's not much harm, and likely a little bit of good that can come
from masks. But the strategy was to get PPE to the front-line health workers
who have a greater need and were in a real crisis, so, the public messaging
was 'no masks'. But the 'truth' of masks started to creep to the fore, more
were asking questions, moreover, the PPE situation started to stabilize a
little bit and 'poof' all of a sudden 'masks are good'. Now they are telling
us? The Canadian Chief Medical Officer literally did a 180 on that, sounding a
lot like Donald Trump in his total about turns. The communications strategy
early on was fairly clear and it made sense, but it's a little uncomfortable
to see your so-called leaders only make decisions 'after everyone else' so as
to avoid taking and risky or blame (Canada wouldn't budget on it until most
other countries did first). If you read the fairly confident communications
about masks from several weeks ago and compare them to the messaging now - you
see a problem that very only makes sense in the context of "purposeful
misdirection for the 'public good' ". Masks did not 'get safer' and nor did
our understanding of them change. What changed was who ostensibly needed them
the most.

~~~
vanniv
The IHME model has been revised every 2-3 days.

It has always assumed that lockdowns would be everywhere and would be
observed.

Every new revision in the last 20 days has been a revision _downward_ in death
rate.

10 days ago, the 95% confidence interval was 100k-240k deaths with lockdowns
observed.

2 days ago it was 45k-145k, with prediction of 81k.

Today is is 37k-137k, with prediction of 60k.

IHME has no incentive to downplay the severity, yet every time the update the
model, they have to adjust it downward because reality had failed to keep up
with the model.

Meanwhile, reporting of fatalities has actually gotten looser, with all deaths
of tested-positive or presumed-positive individuals reported as covid deaths,
regardless of cause or comorbidities (that became universal yesterday, and is
why yesterday saw a big increase in deaths despite a huge dropoff in
hospitalization over the last 6 days)

~~~
chasd00
my pet theory is the malaria drug is actually working. we won't get the final
say until the trials are over however.

~~~
vanniv
It probably is working, but it also seems likely that locking everyone in
their houses reduces spread -- so three weeks after lockdown, there are fewer
sick people to find each day.

It actually is likely that the decrease in cases is more dramatic than the
numbers show -- now that the acute pressure on the healthcare system in New
York has abated, they're probably detecting a higher percentage of their
cases.

(And on top of that, testing has begun increasing again -- we tested 127,000
people today, up from 107,000/day just 6 days ago.)

~~~
vanniv
In case anybody is still looking at the case numbers (especially in NY) and
wondering why they keep kinda not going down even though things look better,
we are actually still increasing testing rates (despite what you may have
heard)

As I said above, we tested 127,000 people yesterday.

We're at 142,000 today already.

~~~
vanniv
... and we're at about 170,000 tests today!

------
thisrod
This seems a bit odd. If it was my job to estimate R₀ for the coronavirus, I'd
look at Singapore, Korea, Australia, New Zealand and so on, where there are
thousands of patients, and almost all of them know when they caught it and who
they caught it from. Why would you choose to study a place where people don't
know those things?

~~~
fspeech
Because that is the definition of R0. Once people are aware and change their
behavior R changes as well and is not readily translatable to a different
setting.

~~~
foogazi
So you want to measure transmission rates under normal interactions, not
during shelter in place/everyone wearing masks?

~~~
eneveu
Yes.

From the article:

 _Dr Feigl-Ding explains that R0 is the “R reproductive number at time 0
before countermeasures”._

 _He points out that this is not the R(effective) at current time under
mitigation measures such as distancing and testing, tracing and quarantine,
which are expected to slash chains of transmission._

------
mmmrtl
Title correction: this isn't a CDC study, just published in a CDC journal

~~~
Scipio_Afri
I think they're pretty reputable, regardless.

"Author affiliations: Los Alamos National Laboratory, Los Alamos, New Mexico,
USA"

------
LatteLazy
If people weren't dying, it would be hilarious had badly understood this
epidemic is. Months since the start, we have no idea how infectious the virus
is, how many people have been infected, how deadly it is, how effective (or
not) containment is, how many people will need to be hospitalised or how long
for.

It's actually incredible. I'm very cynical, but I wouldn't have believed
Western governments could have floundered so badly if I'd been told even a
month ago...

~~~
tbihl
It doesn't help that they leaned heavily on Chinese numbers. Even with data
from southern Europe that is likely to be more accurate, people relied on
numbers coming out of China because they were early and more numerous... But
not enough thought given to openness, and now we've been trying to correct
interpolations and extrapolations with a fraudulent starting point for the
past two months.

~~~
LatteLazy
China causing this should be a massive scandal. China lying about their
numbers so we can't deal with it effectively should be second bigger scandal.

Historically, I've been quite pro China (until they started rounding up
Muslims recently at least). But this is totally unacceptable.

</rant>...

------
bbeez
I hear a lot about how we may be seriously underestimating the CFR
denominator, due to undiagnosed mild cases. Ok I get that.

What I don’t hear much about is that the numerator is also probably
understated at any point in time for several reasons.

First I don’t trust the China data I think it’s understated and that’s the
oldest, most mature data we have.

Second, in an exponentially growing disease with something like a 6 week
course from infection through to mortality/recovery, we will always have
diagnosed cases that are 6 weeks, or whatever the true course is, ahead of the
final death tally and as the diagnosed cases are rising so rapidly, including
those weeks and weeks worth of diagnosed but unresolved cases could add up to
a huge amount of error to a simple deaths/cases CFR analysis that would
significantly understate what the final CFR will look like. Cohort analysis
does not appear to have caught on in the CFR calculation world from what I’ve
been reading.

Third, I’ve read that there are likely a significant number deaths that are
probably attributable to COVID-19 that are not being counted as Covid-19. The
death rate in northern Italy over the last month, even when all the COVID-19
attributed deaths are removed, is significantly higher than it has been in
similar periods in the past I have read. I believe the same is true in New
York City. So if these stories are correct, there are likely more COVID-19
deaths than are being counted.

So while it is probably true that the denominator is understated, it seems to
me that it’s also very likely true that the numerator is also understated
making it very difficult for me to believe any of these estimates are very
accurate until both these issues are addressed.

Has anyone seen anything that explains some of these issues and calculates a
cohort-based death rate, which somehow estimates or adjusts were incorrect,
time shifted or under counted Fatality data?

------
anovikov
No one thought that it depends on people's habits, say common social norms?
Say in Asia it was commonplace to wear masks even before epidemic and it is
considered polite to stand far away from one another, and people bow instead
of shaking hands. Quite clearly there, or say in Sweden with their tradition
of having a large privacy distance, R0 is much lower than in Italy where
people hug and kiss seeing each other.

------
yters
Twice as contagious = half as deadly?

~~~
guscost
Much, much less than half. Contagiousness affects the exponential spread.

~~~
yters
So maybe cov2 is on level with the flu after all.

~~~
guscost
I’m not a doctor, but I’d bet it’s closer to a cold - it spreads much faster,
but may be less lethal. Also, when a virus jumps between species, its
virulence can be elevated during the initial period of spread. So it might be
a “really bad” cold, at least early on:

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4361674/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4361674/)

~~~
yters
I wonder why such panic then.

~~~
guscost
_If_ it's really not that bad, I would guess that the panic is because this is
the first time we've been able to observe a brand-new cold virus as it spreads
around the world. When the general public starts to understand all of the
damage that these things do, and how quickly they can spread, it's
understandably pretty scary. Plus a whole bunch of other factors.

------
AzzieElbab
If that is true China cases will sky rocket again this month.

------
tjansen
There are plenty of anecdotal stories that show that it spreads very quickly.
A highly publicized story in Germany was about one of the first ten cases
here. This guy merely sat behind a patient and got asked for a salt shaker.
That was his only contact. And I know of a company where someone who returned
from a vacation in Italy was in a meeting with 6 people. 5 of them got
infected.

------
Medicalidiot
Here's the study from the Diamond Princess which elucidates what the
percentage of the population is asymptomatic:
[https://www.eurosurveillance.org/content/10.2807/1560-7917.E...](https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2020.25.10.2000180)

------
guscost
And now we wait for the other shoe to drop: serosurveys showing that at least
one-third of the US population has already caught COVID-19 and recovered.

------
cryptonector
Excellent. The faster it moves through, the sooner we'll get back to work.

~~~
tunesmith
You've got to do the math on that. Estimate the percentage of people that have
caught it. Then compare that to how 82% people need to catch it in order to
have the bare minimum of herd immunity. And factor in that health systems in
many regions are already overwhelmed. If you want to get to herd immunity just
from catching it, you'd have a health disaster that is impossible to imagine
even now.

~~~
aaron695
I suspect in 2 years time the death toll will be about the same for everyone.
What we will look at is how countries handled society while it happened.

This 'overwhelmed' the system is a deadly meme, the numbers don't work out.

The best model might be wear masks, physical distance, keep hands clean,
testing and tracing. Ban really large events.

~~~
tunesmith
I don't see how you can say the numbers don't work out, unless you believe
hospital systems are lying when they say they run out of beds/equipment.

~~~
aaron695
Try to work out the actual numbers for strict lockdown vs not strict and model
it over two years being practical. No hand waving.

Include the second and third waves for instance.

You won't see the difference you think.

Vaccines may never happen ( but post a second winter is a best case ) and
treatments don't make things much better.

Once you get 1000000 dead vs 1050000 two years later we can talk about the
additional dead from being unable to do things like cancer surgery.

~~~
tunesmith
Or asthma attacks, or infections from broken arms, or "minor" heart attacks,
or anything else that people can fully recover from but still need immediate
assistance with at risk of death.

You're going to have to show more of your work if you're convinced there's
negligible difference. We know that even now some hospital systems are
overwhelmed, at a point when the worldwide population has room for another
10-13 doublings. We also know that mitigation has already proven to bring
effective R0 down to close to 1.

------
pjkundert
Finally, getting some decent data!

This means that “herd immunity “ is a non-starter: natural immunity through
infection/recovery requires large fractions of the high-risk population to be
infected, and vaccines are too far out (economic destruction would occur
before vaccines _may_ exist).

We must pursue large-scale testing on a “total war” basis, with the goal of
containment and extinguishing the virus.

~~~
jonplackett
Herd immunity was a non-started way before this. Just based on death rate it's
an insane strategy.

Even if the death rate is 1%, then in the USA, to have even 60% infected and
recover, you need to have 192 million infected.

1% death rate = nearly 2 million dead.

But it would be way higher than 1% death rate with these sort of numbers
because most of these people are not even getting a hospital bed, never mind
ICU.

~~~
k__
Didn't a study show that the death rate is a magnitude lower than previously
thought? Something like 0,6% IIRC.

~~~
deviantfero
even if the death rate is that low, you have to account for the fact that
health systems in first world countries are overloading with the initial
stages of the spread, leading to more people dying because there's no medical
attention to patients who would otherwise make it through the disease.

~~~
jonplackett
In Italy they have 10% of people who they know have the virus dying
(deliberately not calling this death rate) but they are testing pretty well
and that seems very, very high. Can there be 10X more people with the virus
than they know about? Not sure.

Also, OK let's call it 0.6%. Only just over a million deaths in the US alone
then, even before health systems overwhelmed.

Still a non-starter in my book.

~~~
specialp
Italy is testing at a rate less than NY. I live in NY and I personally know
over a dozen people with presumed COVID-19. Only one has been tested as he is
a first responder.. The others are not in the stats. I know this is anecdotal
but it appears that there are WAY more people that have this than the official
tested positive number.

It seems once this takes a hold in an area that it really gets a lot of
people. Me and my wife also had lung congestion, cough and brief fever but
will never know if we had it until widespread antibody testing occurs. But it
seems very likely there are many more cases than reported and 10x could be
possible.

~~~
Marsymars
Conversely, my jurisdiction (Alberta) has been testing a lot of symptomatic
people, and ~98% of people with COVID-19 symptoms have tested negative.

~~~
rwmurrayVT
In VA we've done 30,645 tests and have 3,645 confirmed cases. That tells me
that 88% of people tested were negative. Either they're spreading a whole lot
of "potentially" exposed people or there are a lot of people with symptoms who
actually have something else.

