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Antiviral drugs for the flu | Infectious diseases | Health & Medicine | Khan Academy

October 18, 2019

I’m going to quickly
sketch out a flu virus for you–
something like this. And it has an envelope, so
this is our little envelope. And on the inside
of this envelope are eight chunks of RNA,
so let’s draw out the RNA. This is the genetic material. And this genetic material,
among other things, codes for protein. And so one of the proteins
here is sitting on the outside. I’m drawing it as if it
looks like a little hand. And the reason I do that is
because it reminds me that this H stands for hemagglutinin, but
it basically holds onto sialic acid . And that’s how it gets
inside of little cells. And then there’s another
protein over here. And I draw these as
a pair of scissors just to kind of remind me that
this one nicks the sialic acid. This is called neuraminidase,
and it nicks the sialic acid, and it helps it cut itself
loose from the cell. And so it can move on
to other cells- kind of helps with exiting. And I haven’t actually been
drawing this other protein. There’s another one here. And I’m going to draw it now. This is called an M2 protein. But it’s not actually
found on all flu types. It’s actually found
on flu A, but actually not found on flu B. So this is
a really important difference between flu A and flu B. And you’ll see why, because
one of the medicines that we use now to treat flu– and
yes, you heard me correctly, that we do have
anti-viral medications. You probably heard
from many people saying antibiotics
only treat bacteria, not viruses, and that’s true. But we have a special
word for these other drugs that actually do treat viruses. And we call them
anti-viral drugs. And there are couple of them. I’m actually going to write
out some of the names. So this is called
Amantadine or Rimantadine. And it’s kind of
easy to remember that they are in the
same class because they share a lot of the same letters. And these two anti-viral
drugs, they actually work on stopping or blocking
the activity of this enzyme. And I’m just kind of drawing
it like a little negative sign. But that’s just to remind
you that it blocks the M2. So if you know that
flu B doesn’t have M2, then you also know
that these drugs then don’t work against flu B. These drugs don’t even work
that well against flu A, because flu A has
become quite resistant. So remember, resistance
happens because there are little mutations. And it turns out that flu A has
kind of a mutated form of M2, so that it actually doesn’t
get blocked by Amantadine or Rimantadine quite so easily. So unfortunately for
us, that’s bad news. And the CDC in 2012,
2013 have recommended not using these
drugs because there’s so much flu A resistance. So that’s unfortunate,
but the good news is that we actually have
a couple of other drugs. So we have a drug
called Oseltamivir, and related to
it– and you’ll see with the spelling–
we have Zanamivir. And these, of course, share a
lot of the same letters again. And these two actually
block the neuraminidase. And this is actually
in flu A and flu B. So that’s good news, because
it blocks both flu A and flu B. And let me actually just
write that down, flu A and flu B. And that’s important, right? So we have these two drugs,
and one of them is a pill. This first one is a pill. And the second one is
kind of an inhaled powder. So they’re taken
in different ways. And another important
difference between them– this is something that we have
to just kind of keep in mind– is that there are
age restrictions. So you have to be
a certain age to be able to take these medications. And they differ
between the two drugs, and whether you’re
using it to treat, or if you’re using it to prevent
getting sick from the flu. There’s a difference there too. So there are age
restrictions that we just have to keep in mind. But overall, I’m pretty
happy with the fact that at least we
have these options if we need to treat someone
that’s very sick from the flu. So let’s talk about
that treatment then. So what if you have someone–
and this happens to me all the time where someone comes
in kind of frowny faced because they’re sick with
the flu, and you’re thinking, OK well, this person
obviously needs treatment. So I’m going to write
that at the top. They need some
sort of treatment. And I guess the
first question is, why would I treat this person? Of course, everyone’s
going to be frowny faced if they get the flu. So why am I treating
this person? What makes them so special? Well, one thing that
could make them special is– let’s say that
they’re high risk. Remember high risk groups in
our society, in our community, include real young
kids– so let’s say under two years
old– or older folks– let’s say people
over 65 years old. It could be someone
that’s pregnant. That’s another high risk group. Or it could be someone that has
some sort of chronic disease. And that could be like a
lung disease or asthma, any sort of chronic disease
that makes them ill. Maybe their immune
system isn’t working. And that would be a
group I would definitely consider treatment for. Now another group– I’m
going to put it just right below– is let’s say
you have someone that’s completely healthy– young,
healthy person, not pregnant. They still might get
treatment if there’s maybe severe disease. Let’s say they get
really, really sick. They’re just feeling awful,
and I’m worried about them, and they might need
to be hospitalized. If they’re very,
very sick, or they get some sort of
complication, or they’re going to get hospitalization,
anything like that, then this is a person, again,
I would be careful with. And I would consider treatment. Let me bring up a
little bit of space. So this is the kind of group
that I would definitely consider treatment in. So what else should we
think about or consider? Well, the next question,
often, that comes up is how soon do you need
to start treatment? When do you need
to begin treatment? Or when do you start? And of course that
answer’s going to be as soon as possible. But a bigger range on that
would be within two days. So really, if they’ve started
getting symptoms a week ago, I might still be
inclined to treat them. But I’d be more inclined
if it had just started. What other questions
or considerations should we just
kind of go through? What about treatment? So how long do you
treat them for? And generally speaking,
it’s about five days. So five days of either
Oseltamivir or Zanamivir. And sometimes it goes
a little bit longer, but usually it’s just five days. That’s kind of a normal course. So this is how I
would manage someone that’s being treated for flu. But of course, what if they’re
not being treated for it? What if they come in,
and they’re feeling fine? And we have to draw
another face here. This is a smiley face,
something like that. And I’m going to draw two. So let’s say there’s two. And we’re going to deal
with them separately. So let me actually draw
a line between them, something like this. So we’ve got two more cases. Both are feeling fine, but
they might need prevention. Another thing these drugs
can do is prevent you from getting sick. So prevention is
important as well. And let’s say these folks
are living in a home. Let me actually build
a little nice house around my first
smiley face person. And I’ll do the same around
this second smiley face person. And let’s say this
first person– this person gets a
visit from someone who’s feeling flu symptoms. So this person comes to
visit, and our friend, our smiley friend, is worried. They think, oh my gosh,
now I’m going to get sick. So if they’re high
risk– and we went through some of the
categories– actually, I should mention there are
other categories, not just these that I listed. There are some others as well. But if they’re high
risk in some way, then I would
consider giving them a medication like
Oseltamivir or Zanamivir to prevent them
from getting sick. Now this whole bit about severe
disease or hospitalization– this doesn’t really apply
because they’re not sick. They’re obviously not going
to have severe disease or hospitalization already. What about this question of
when would I start treatment. Well ideally, again, it’s
going to be within two days. So within two days
of their exposure. We call the visit,
or whoever kind of made them worry that
they might get the flu, we call that the exposure. And so really you want to start
treatment within two days. And you also want to start
prevention within two days. So how long would you actually
give them the medications for, to prevent them
from getting sick? Well it really depends
on whether or not they’ve had the vaccine. So let’s say they’ve had the
vaccine, the flu vaccine. And they were high risk. They got visited by
someone, or had an exposure. For this person,
I’m thinking I want to treat them for two weeks. Or give them two
weeks of medications. And the logic is that if
I kept them two weeks, then that basically covers them. And then after
that, I would assume that the vaccine would
kind of take hold. Because remember, the
vaccine takes two weeks to really take full effect. So basically, I give
them a medication during that period of time when
the vaccine isn’t completely protecting them. And then I expect their
vaccine to kind of take over, and for the rest
of the flu season, presumably, they should
have good protection. So that would be my strategy. Now let’s say that they can
not take the vaccine, so no vaccine. And maybe this person
has a severe allergy, or had a horrible
reaction to the vaccine. For whatever reason, they
cannot take the vaccine. Well in this person, if
they can’t take the vaccine, or don’t have the vaccine,
then for this person I would actually treat
them for just one week. One week after exposure. So if the exposure
happened, let’s say today, I would basically–
and then let’s assume it’s not going
to keep happening– so one week after exposure
would then make it next week, is when I would
stop the medication. So in this scenario,
I’m protecting them with the medication
against getting sick from this exposure. But because they’ve
had no vaccine, if they have ongoing
exposures– let’s say they get exposed again
to flu in three weeks– then again they’d have
to come back to me, and we’d have to do
this all over again. So it really is ideal to have
that vaccine in your system to keep protecting
you and preventing you from getting ill. Now in this second
scenario, let’s say instead of having a
visitor who’s sick, let’s say you’ve got people
around you that are sick, living in the same place as you. Now this person is obviously in
the home with a group of folks. So let’s call that a group home. And what we call this scenario
is basically an outbreak. So this person is living
in an outbreak setting. And many, many people with
flu are living together causing an outbreak to happen. We really are worried
about other healthy people like our smiley faced friend
from getting sick with the flu as well. So in this setting,
who am I worried about? Who do I want to make sure gets
medications to prevent them from getting sick? Well, we’ve got high risk
people, again, living together. So if people are
living together– and this could be
senior citizens, or could be a chronic care
facility, or nursing home– and really any kind
of group setting where people are
institutionalized and they’re high risk,
I’m going to be worried. And I want to make sure
that we consider prevention with one of these medications,
the Oseltamivir or Zanamivir. And do I have to worry
about severe disease or hospitalization? Well, no, again because
here specifically I’m talking about
the healthy person who happens to be
in an outbreak. So they’re still healthy. They’re not hospitalized. They don’t have
severe disease yet. So the whole idea
is to make sure they don’t get those things, right? And when would I
want to treat them? Well, it’s hard to really
say within two days because that implies that
something specific is happening. When in fact,
during an outbreak, you just have constant
exposure, right? I mean, everyone
around you is sick. Let’s say you go down
to eat in the cafeteria. Everyone is sick. So when you’re having
constant exposure, we don’t really think
about within two days. It doesn’t really
make sense here. So here I would just
kind of be worried in general about this person. And as far as
treatment, you really end up just treating everybody. Vaccine or no vaccine,
you treat everybody throughout the outbreak
because the whole goal here is really to minimize
the outbreak. You don’t want people to have
all the horrible consequences of flu. Remember, flu can kill people,
and can cause hospitalizations. So to prevent all that,
because it’s a high risk group of people living
together, you would really just treat throughout the outbreak. And even one week after the
last case of flu is found. So here, unlike
the scenario where you have just a single
exposure, because you have so many people in
an outbreak that are sick and kind of exposing
each other, you basically just treat everybody with
Oseltamivir or Zanamivir. So now you see we have a
couple of anti-viral drugs, and you see when we can
use them to treat folks, and also when we can use
them to prevent folks from getting sick.


  • Reply maryam17123 February 2, 2013 at 5:32 pm

    Great video

  • Reply Alex Nguyen May 19, 2013 at 1:04 am

    dude you have amazing handwriting

  • Reply Reava Felix July 31, 2013 at 2:58 pm

    my professor recommended that i watch this video and i thought it was going to boring but this is a pretty amazing video

  • Reply Ali Shakeel November 22, 2013 at 4:03 pm

    this was posted in the future 😀

  • Reply Ali and Mohammed Basheer November 15, 2016 at 7:45 pm


  • Reply Farhad Babaie April 18, 2017 at 9:25 am

    grate teaching thx

  • Reply Sean Ngui May 21, 2017 at 3:04 am

    I don't understand, so if a healthy patient comes to you without having a flu vaccination, how do you explain to them that they receive less treatment than the person who's had the vaccine ?

  • Reply alexandra tuminaro July 27, 2017 at 12:06 am

    is the person writing this on the video left handed ?

  • Reply Dr.umair Razzaq November 6, 2017 at 2:56 am

    Please tell us about dose ?

  • Reply Frank M January 7, 2018 at 11:43 pm

    Enjoyed this very much and was explained Thoroughly, thank you

  • Reply MrEthanhines February 3, 2018 at 11:56 pm

    Why is there a "Window Period" like PEP in HIV? I can see with HIV why (integration of viral DNA into cells) but what about Influenza A? It doesn't incorporate it's genetic code into a cell. So why does it matter that Tamiflu be given within 48hrs (like HIV)

  • Reply Abhinav Chaudhary April 24, 2018 at 4:28 am

    Reply to me if you know the answer, is it true that we don't really know how anesthesia work

  • Reply Rattam Gaming June 16, 2018 at 7:22 am

    which antivirus for pneumonia viral?

  • Reply GODS OWN LUNATICS June 16, 2018 at 9:23 am

    bacon, them red squiggly lines look like bacon

  • Reply crookback October 1, 2018 at 5:56 pm

    watching this because tamiflu fucked me up bad, like i was going towards the light when i took this drug twice daily

  • Reply Palesa Esuk November 4, 2018 at 6:13 pm

    I just wanted one about treatment in general—__——

  • Reply Faiza May 16, 2019 at 7:53 am

    Watching this before 4 hours of Final Exam

  • Reply Thang Khiam September 28, 2019 at 10:16 am

    wonder teaching, the background is kind to the eyes. every word spoken is fascinating!

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