welcome to another MedCram update on the corona virus as of yesterday it was
170 deaths and seven thousand seven hundred and eighty three confirmed
infectious cases this update is for January 31st 2020 and so overnight we've
gone to unfortunately 213 deaths and nine thousand seven hundred and seventy
six confirmed infections most of those in mainland China this data is coming
from the w-h-o and other health care agencies coming together it's about a
twenty six percent increase in the number it confirmed infections and a 26
percent increase in the number of deaths now I notice I've got a lot of comments
about the potential fallacy of dividing the numerator here which is the number
of deaths which is current divided by the number of infections which may have
not matured to the effect that they may have caused mortality because it may be
too early in the course and I understand that and a lot of people do understand
that the problem is is though is the incubation period can vary quite long
and so you know do you go back one week to see what the case infection rate is
do you go back three days and so if you really want to figure out what this is
of course you wait to the very end until the epidemic is over will which will
hopefully be very soon and then you take that numerator and divide it by that
denominator and you will get what the case fatality rate is unfortunate we
can't do that in the middle of it and as we'll talk about very shortly the
incubation may not be as long as we think which is fortunately a good thing
however there's a trade-off in this situation as we'll talk about in the
Germany case very shortly where there may be asymptomatic shedding of the
virus and that brings us to the other point is yes well there may be an
underestimation of the mortality rate by looking at the current numerator and
dividing it by the current denominator there's also the possibility of way
overestimating the mortality rate if there's a bunch of asymptomatic
infections where people get it and they get better then this denominator down
here is actually way bigger and we think it is if that's the case
well then this mortality rate is much less than 2% it's hard to say exactly
what it is at this point suffice to say that if you want to look at an easy way
of comparing how the mortality rate is changing over time simply take the
current fatality rate and divide it by the current estimated infection rate
we're probably under estimating both the numerator and the denominator here
because there's just not enough kits to go around the test everybody if you
think about it in China they're not going to be testing people who might
have a little bit of malaise if they've got a hospital full of people with
pneumonia those are the ones that are gonna get tested and so what you may be
seeing here in China is people who are very ill getting tested for the corona
virus and that may make the mortality rate go higher because you're
selectively testing people that are sicker whereas here in the United States
we're testing anybody who sneezes wrong that's come from China and so we may be
picking up a lot of asymptomatic cases and that may be the reason why all of
the deaths that we are seeing are almost exclusively from China and nobody
outside of China in the United States nobody has really come down with a
serious illness so these are observations these are not facts we
don't know yet these are hypotheses so to keep it simple we're gonna go ahead
with the current mortality rate divide it by the current infection rate not
saying that that is the mortality rate but it's certainly a way to track it and
so you're comparing apples to apples but the total infection rate is way past
SARS now we are treading on new territory when it comes to viral
epidemics and that brings us to the other news which of course the w-h-o has
now said that this is a serious global emergency in terms of a virus now the
other big news today is in Riverside which is close to home for me because
that's the county that I work in in Southern California and actually worked
with the Public Health Officer for Riverside County dr. Kaiser
who today had to forcibly quarantine a patient who was on the march Air Reserve
Base who wanted to leave and of course that caused him to be in
isolation until deemed unnecessary or two weeks so what they're currently
doing right now in March air reserve base is this plane which has about a
hundred and ninety five passengers are now voluntarily except for one because
he tried to leave staying on the base for 72 hours and during that time
they're doing a lot of screening they are checking for temperature they're
doing nasal swabs at the end of those 72 hours if everything is a-okay then they
are free to go of course you may say a hot that are in Southern California let
them stay in Southern California well these people are from all over the
United States and I'm sure as soon as they are let go they will be coming to
your area of the woods so let's explore a little bit about what's happened in
terms of our knowledge over the last couple of days over this virus and how
it behaves in terms of incubation period and in terms of the type of illnesses
that it causes and also the ability for it to shet because there's a lot of
interesting information that we're about to get into here that has been published
recently in the New England Journal of Medicine and it's hot off the press we
will give you a link in the description below but let's get into that okay so
this is a drawing that is based on a figure in that New England Journal of
Medicine article on what we've got is five people here we got the index
patient and we've got patient one two three four and this is all happening in
Germany and these are all dates in January here below okay so the first
thing that happened here is that there was a business meeting that was
occurring and this index patient here was actually from China and they flew
over to Germany to have an attend a business meeting and this meeting
occurred over the period of the 19th to the 22nd so who was at that business
meeting well these two people here who are German natives attended the business
meeting with index patients
everything was fine nobody was having symptoms and the index patient while she
hopped on a flight on the 22nd here and goes back to China and starts developing
symptoms almost immediately after she gets on the flight okay she goes back to
China and of course there's the big rage of what's going on and she has the
symptoms so what does she do she goes and gets tested and she goes and gets
tested over here on the 26th meanwhile what happens is patient number one who
was at the meeting he starts developing symptoms on the 24th mild symptoms so a
cough fever malaise all the sorts of things that you would assume would go
along with the flu and his symptoms get worse and then they get better now index
patient she gets tested here on the 26th PCR and it's positive as soon as it gets
positive she goes back and she calls her company and they do it a traceback to
try to figure out all the people that she may have come in contact with so
they can figure out where to test and of course by this point
patient number ones like well yeah I had a little bit of flu symptoms but I'm
fine now so they check him the next day on the 27th okay PCR positive boom
but he's asymptomatic he's gotten better from his mild symptoms they're really
not that bad anymore nevertheless they go ahead and they test him they check
for viral loads they see if there's virus in his saliva virus in his sputum
and guess what he has a high viral load even though he is not symptomatic in
other words he is contagious and they find up to ten to the eighth viral
particles per milliliter that's pretty high well guess what
patient two three and four they all start developing symptoms as well during
the same time patient two symptoms lasts a little bit longer and they test on the
twenty-eighth of course when he turns out positive all hell breaks loose and
they're like wow what's going on here and so a whole bunch of other people get
and so sure enough patient two has a positive PCR but remember this patient
number two attended the same meetings and so it's very possible that this is
how it worked okay but here's the point that should blow you away
patient three and four never attended the meetings
however patient three and four did have contact with patient number one and they
can actually map out when patient three and four had contact with patient number
one and all of these contacts were before the patient actually had symptoms
so in other words three and four started to develop symptoms but they started to
develop symptoms later about a day later so they developed symptoms on January
25th January 26th and of course they got tested with everybody else because they
were all freaking out of course and sure enough PCR was positive so here's the
take home message number one it looks as though the incubation period here is
fairly short so that's a good thing that means that you're going to find out
quickly whether or not the patient has a virus what's bad about this though is
that you're able to spread the virus both before and after it seems you have
symptoms in fact we know that patient three and four got their virus from a
patient who got it from the index patient here and they got it before they
had symptoms so this begs the question and it's a very interesting question
about what are we doing at March Air Reserve Base yes if we were to watch
them for 72 hours which of course is three days we should be able to pick up
if any of them have symptoms fevers anything of that nature but the question
is do we release them after 72 hours if they're all clean and I think the debate
is still going on that should you hold them for two weeks yeah that would be
safer for everybody but you have to weigh the practicalities of holding them
for 72 hours versus two we and do you really need to do that if it
looks as though the incubation period here is pretty short so what are the big
take-home messages from this New England Journal of Medicine article number one
the incubation period seems to be relatively short maybe three or four
days could be longer could be shorter but that seems to be what we're seeing
here number two even though you're asymptomatic it seems pretty clear that
you're able to shed and infect somebody else with the virus number three it
seems as though at least here in this short cohort of four people that all of
these people had very mild symptoms everyone here so far is not in the
hospital they're not on a ventilator they seem to be doing just fine these
were healthy people though in Germany so it's sometimes hard to actually
generalize this to everyone all right more updates as they come thank you for
joining us