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last week the World Health Organization
announced that the fatality rate of
Kovan 19 is higher than we thought on
March 3rd they noted that worldwide
about 3.4 percent of the people who had
contracted the infection had died from
it instead of the 2% figure that had
been making the rounds there have been
all kinds of reactions to that but no
matter how you feel the key thing to
understand is that this number is fluid
and squishy not some unchanging property
of the virus right now we don't know how
deadly this outbreak will be globally
because predicting epidemics is really
hard but what we all do right now can
have a big impact on the final toll you
might think pinning down how dangerous
are diseases or what epidemiologists
would call its virulence would be pretty
straight forward after all some
statistics that get at this like case
fatality rate or ratio are deceptively
simple you just take the number of
deaths divided by the number of cases
and boom you have the CFR and can go
about comparing it to other outbreaks
for example you might have seen people
saying that on average the seasonal flu
zfr is only about 0.1% which makes the
new corona virus 34 times as dangerous
but that comparison is misleading and
the flus fatality rate can vary between
seasons and kovat nineteen's is likely
to change sia viruses deadliness varies
based on the unique circumstances of an
outbreak and we've been very wrong in
the past when we've tried to predict the
CFR too early on the one hand that 3.4
number could be an underestimate because
kovat 19 isn't instantly fatal people
who have died so far have done so two to
eight weeks after their first symptoms
so some of the people currently counted
as survivors might not end up that way
on the other hand it might be an
overestimate because most areas are only
testing people who are clearly
symptomatic so the CFR might not be
taking into account a large number of
symptomless and mild cases because of
these and other sources of error experts
say it can take months before you can
accurately predict the eventual CFR for
a particular outbreak so it may be too
soon to tell where kovat 19 will fall
like right now experts disagree about
how many milder cases are being
overlooked some think there aren't a
whole lot while others think there are
tons enough that the actual CFR is
already below 1% that seems to be the
case in South Korea for example where
health officials had diligently tested
196 thousand people as of March 9th
their CFR is hovering around 0.7% that
might go up a bit if people who are very
sick right now don't pull through but it
may never hit that global average of 3.4
percent which brings us to another
reason CFR's can be a bit misleading
they can vary a lot geographically for
example within China the CFR of kovat 19
has varied from about 4 percent to less
than one person part of the reason for
that is that things outside of the
disease itself like public health
infrastructure resources and policies
can have an impact on fatality rates
that's because deaths tend to creep
upward when health systems become
overburdened if there aren't enough
doctors hospital beds and supplies to
give every person with serious symptoms
the best care then people may die who
would not have otherwise this is why you
see a lot of people harping on about flu
shots in places like the u.s. the two
diseases have similar symptoms so
treating flu cases can drain resources
needed for treating kovat 19 and non
disease factors are why it could be
really helpful to slow the spread of
kovat 19 even if we can't stop it this
is what everyone on Twitter is referring
to with the hashtag flatten the curve
the idea being that overall the same
number of people might get infected with
the virus but if the cases trickle in
they're less likely to drown facilities
and that means more people may survive
so just by washing your hands a lot and
staying home if you're sick you can help
free up resources so health care workers
can focus on patients with kovat 19 I
mean that's not the only reason to do
those things
you'll also reduce the odds that you'll
get the virus which might be worse for
you personally than the CFR suggests or
better CC FRS can help public health
professionals figure out how to best
respond to an emerging disease but they
don't do a great job of conveying your
individual risk
let's compare kovat 19 to the seasonal
flu again because well everybody seems
to want to do that even if both diseases
had the same CFR
might not pose equal risks to you
influenza tends to hit both ends of the
age spectrum pretty hard but kovat 19
has kind of ignored younger folks so far
no one under the age of 10 died in the
first 100,000 cases meanwhile this
year's flu has killed 125 kids
and been especially bad for children in
general we don't fully understand why
these diseases have such different
effects on young humans but it may have
something to do with how developing
immune systems react to different kinds
of viruses researchers have found that
the immune systems of older mice react
more strongly to corona viruses than
those of younger mice something similar
could happen in humans and an immune
response that's too strong can
predispose people to the deadlier
symptoms of respiratory infections
aside from age things like other health
conditions and past infections might
influence how you react to being
infected by this new corona virus you
can't get any of that from the overall
case fatality rate plus you don't have
to die for a disease to wreak havoc on
your life
in fact some research is trying to
quantify the severity of an outbreak by
measuring other things like the
hospitalization rate instead of just
fatalities no matter what even if your
individual risk of a severe corona virus
infection is low we should all take the
epidemic seriously because what we do
right now matters we have the chance to
shape how this plays out and if we do
all those things you keep hearing about
like getting a flu shot staying home
when you're sick and washing your hands
well and often we can keep this thing
from becoming the worst case scenario
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