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How Influenza Pandemics Occur

okay well welcome to another
MedCram lecture today we're going to talk about the flu and the flu is
something that we see seasonally and I'd like to talk about specifically the
virus the strains the symptoms assigns the vaccine and treatment see if we can
give you a primer here on the influenza virus okay so first of all there is a
virus it's divided into different strains there is a type A and a type B
strain the one that you've got to look out for in the type a is the one that
seems to be most common anyway is the h3 and 2 strain but we also see the h1n1
that's the one that we're most concerned about that's one that seems to be
associated with epidemics what are the signs and symptoms so how
do you can you tell this from the cold viruses and of course you do get respiratory
symptoms but the other thing that is really key is muscle aches so that's a key one you could also see
nausea and vomiting the other thing that you might see is pneumonia and so I've
seen people with the flu developed such a severe pneumonia that they actually go
into AR D s and respiratory failure and this is what kills a lot of people so as
a result of that what we do is we try to prevent this by using a vaccine okay so
the flu vaccine usually becomes available in October and it goes
throughout the end of the year and into the new year until late winter that you
can get the vaccine so the the vaccine usually is trivalent which means that
there are three different types of viruses that are in there and in the
year most recently here in 2017 to 2018 for instance the the three types there's
usually two type AIDS that they put in there and one type B and the type a they
always seem to put in h1n1 and that's through research that they look at out
there to see what is most likely to come across and this talk is going to be a
little bit American centric here because of recommendations from the FDA and the
CDC which are both in the United States the other one that they do is h3 and –
and you may recall that's the one that we talked about over here there's so
many different strains of each one of these though that they could actually
put in one type of h3 and – for instance like the Hong Kong one and it could come
out with something completely different there's also a B in the year that I'm
talking about they did the Brisbane strain for that sometimes they'll do
four different ones and if it's the four and the year we're talking about 2017 to
2018 they added an extra B in there so either three or four usually a couple of
a's couple of B's try to hit the nail on the head sometimes it works and
sometimes it doesn't work so that's just one of the things to be aware of so how
do you make the diagnosis let's say somebody comes in with these symptoms
how do you make the diagnosis of the flu well the two major ways of doing it is
using something called the R I DT okay and the other one is using reverse
transcriptase PC R this one here the RI DT can be done in about 10 to 15 minutes
in the emergency room the problem is is though is that if this is negative
because the sensitivity is not very high if it's negative you can't rule it out
so if you've got a patient during an epidemic who's coming in with classic
signs and symptoms it's better to treat them than it is to wait for the RI DT or
even the rt-pcr the rit pcr is extremely sensitive so if it's negative that one
you can rule out remember spin and snout just as a little aside SP means specific
if something is very specific you can rule it in and then snout sensitive if
it is something is very sensitive then you can rule it out well that means if
it's not sensitive you can't rule it out the RI DT is not very sensitive and so
you cannot rule things out with a negative RI DT however if you have a
very sensitive test like the rt-pcr and it is negative then since because it is
very sensitive you can rule it out so just be aware of that
however in times of an epidemic people are pouring into the emergency room with
respiratory symptoms and they're all being tested and they're all being
positive for the for instance the h3n2 if these people are coming in it's
better to get the medication on board right away
because the sooner you get antiviral medications on and we'll talk about
those the sooner you get those on like for instance less than 48 hours from the
onset of symptoms the more likely you're going to get a benefit from taking some
of these antiviral medications so how effective are these antiviral
medications we'll talk about treatment over here if we look at treatments and
we'll switch to different color here there's basically three different types
of medications that we can give for treatment they're all something called
neuraminidase inhibitors Andy you are a men days inhibitors okay and what are
those three ones that we we should be using during the flu epidemic well the
first one is au cell Tam of there I'll talk about that one that's known as
Tamiflu okay the next one is known as za na mi vir the name of air and that is
known as the inhaler one which is relent okay and then the last one is P er a-m I
VI R pyramid of error and that one is known as rap of AB okay so the Tamiflu
or oseltamivir is an oral either capsule or solution Zen nimah vert is an inhaled
and parameter or rabbim AB is intravenous now the thing you should
know about is that all of these medications here are all greater than
99% effective for type A and for type B virus so a and B and when I say
effective it's been shown to reduce the symptoms of uncomplicated viral flu by
24 hours which doesn't seem like a lot but it is
important in that if you can reduce the infectivity you can reduce the spread the thing I do want to make very clear
though early on here is that there are two medications that have been used for
viruses in the past that really don't have any role in treating the flu and
they are amantadine and rimantadine there is just way too much resistance
against these two medications in the more recent strains of the influenza
virus okay so let's talk a little bit more in a little bit more detail about
these three medications and about how they're used and the dose and things of
that nature okay let's talk about the first one
which is Tamiflu or o sell Tam up there which is why otherwise known as Tamiflu
and what we'll do here is we'll draw the treatment on the top line and we'll draw
prophylaxis on the bottom what we mean by prophylaxis there is that if you have
a close contact that has been exposed to it and it's had the flu and you want to
take it to avoid getting it from them that's chemo prophylaxis or in this case
prophylaxis okay so starting at zero years of age here what we're going to do
is we're going to break this up into different sections so this is going to
be at two weeks this is going to be here at three months this will be here at one
year and that'll be further on so the
treatment is 75 milligrams P o Q 12 hours times five days and the
prophylaxis dose is 75 milligrams P o Q day and it could be anywhere from seven
days all the way up through ten days all the way up to six weeks if necessary
depending on this clinical situation now the thing that's interest
thing about this is that there are some recommendations and differences in terms
of who should get treatment and who can get prophylaxis and then the reason why
I drew this out was to show you the difference between these two so the FDA
has approved this drug basically for any patient that is greater than two weeks
old can get this medication now for adults
this is the dose okay for children you're gonna have to look up the dose
because it's all weight based so just be aware that but for treatment purposes
the FDA recommends treatment all the way down to two weeks of age and no upper
limit what have you do for patients who are less than two weeks of age well the
FDA didn't test it or approve it for that but the CDC and the American
Academy of Pediatrics does recommend because of data that you can treat less
than two weeks of age now in terms of prophylaxis the FDA recommends all the
way down to one year so you can prophylaxis um one with Tamiflu in other
words if somebody contracted it and you are next to them and you want to make
sure that you don't get it or your patient doesn't get it you can give this
medication in this dose and you can look up the prophylactic dosing for
Pediatrics as well all the way down to one year of age and again the CDC goes a
little bit further because of data so the CDC and the American Academy of
Pediatrics would say well we're going to go even less than one year we can go all
the way down to three months of age okay now the question is is what do you do
for prophylaxis here and that's really going to be left up to the severity of
the case and the physician and the decision that they make at that point in
terms of prophylaxis so I wanted to make sure that you understood when
tamiflu could be used in these situations whether you're using it for
treatments whether you're using it for prophylaxis and knowing these dosages
based on the weight you've got to look those up and knowing what the FDA has
actually approved this drug to be used for but what the CDC and the American
Academy of Pediatrics recommends you should know that Tamiflu comes in a
capsule but you can also get it in oral solution that you can swallow so think
about this in terms of ventilated patients who have og tubes
think about this in terms of patients who can swallow okay the next note we're
going to talk about is inhaled it's Anam of air otherwise known as Relenza the
first thing you've got to know about this medication it's not for patients
who are hospitalized so not for hospitalized the other thing that you
should know is that it's really for patients who don't have COPD so not for
patients with COPD or asthma okay these patients this is not good a Bronco
dilated in fact it may do the opposite so you've got to be careful about it
okay so we're going to divide this one up into five years and seven years so
again the FDA is recommending in terms of treatments so we've got treatments
and we've got prophylaxis here again same idea so the FDA allows treatments
all the way down to seven years of age okay so you can treat it's FDA approved
for that the FDA has also approved the prophylaxis all the way down to five
years of age okay there is no CDC recommendation here or American Academy
of Pediatrics so you're really kind of on your own and wouldn't recommend it so
the FDA is only allowing you to treat with this medication down to seven years
and prophylaxis and then of course what is the actual
treatment well it's an inhaler so it's two puffs q twelve hours here whereas
prophylaxis is two puffs q twenty-four hours and this one is five days the
treatment is five days and here it is ten days okay let's talk about the last
neuraminidase inhibitor and that one is paramah there otherwise known as wrap of
AB and for this one the division is actually pretty easy to understand okay
once again we've got treatment here on the top and prophylaxis on the bottom
and the FDA and the cutoff here is two years and the dose is actually 600
milligrams IV believe it or not times one dose okay now you've got to be
careful because there is renal dosing that you've got to look up FDA approves
the use of this medication all the way down to two years of age for treatment
purposes okay below that age there is no
recommendation and furthermore there is no recommendation of course to give this
intravenously for prophylaxis so just be aware of that issue okay so going back
to the flu we talked about the different types of viruses the different symptoms
the vaccine what we're actually trying to get in the vaccine how do you make
the diagnosis I think the key here is understanding the medications that you
have access to and quick observation and quick identification of these patients
as they're coming into the emergency room especially in an epidemic that you
really want to treat these patients really before you have the results in
hand you can always stop the medications if you have to because the earlier the
treatment typically less than 48 hours after onset the better the outcome is
going to be however if it's been more than 48 hours I'd still recommend
starting them especially in severe patient
there was a question a number of years ago as to whether a higher dose would
have made an improved difference in outcomes in the very severe hospitalized
ICU patients and I think the data on that is showing that really the higher
dose doesn't improve outcomes so I think you should stick with the current
published doses that is the flu thanks for joining us