- [Voiceover] So if you're watching this video,
I'm pretty sure that at some point in your life,
or in the lives of someone you know,
that you've had the flu.
Almost everybody is pretty familiar
with how awful it feels to get sick with the flu.
And when people talk about the flu,
they kinda talk about it in two different ways.
And we're gonna get into both of those ways right now.
So sometimes, they'll talk about the illness,
or the symptoms they had when they had the flu.
And other times, they'll talk about the virus,
you know, the actual virus that causes the flu.
So I'm gonna actually break it down the same way,
we're gonna talk first about the illness,
and then we're gonna get into the virus.
I'm gonna draw a nice little line down the middle
so that we don't get lost in this conversation.
So I can't help it, but any time I hear
that someone has the flu,
I immediately get into this mode
where I have a bunch of questions for them,
and I really just wanna kinda convince myself
that when they say they have the flu,
they really have the flu and they don't have something else.
So the questions that pop up in my head,
the first one is usually, is it abrupt,
or did it kinda start abruptly?
I'm gonna just write that.
Was it abrupt?
And you know, I might say,
do you remember feeling well one evening,
and then waking up sick.
Or something like that.
Do you remember exactly kinda when it started.
And most people with the flu can tell you,
within a day or two,
exactly when their illness started.
Now another clue that something is the flu
is that it usually lasts for about three to seven days.
So if someone is saying,
well, I got sick with the flu,
and then four months later,
you know, I started getting better,
that's a very weird story.
Usually it would be a lot quicker than that.
So always think around three to seven days.
Of course it could be a few extra days than that,
especially when you're thinking
about a symptom like the cough.
But generally speaking, that's the time window.
Then I really get into the symptoms themselves.
I want to find out exactly what made them feel so sick.
And there are two categories of symptoms.
The first is respiratory symptoms.
I want to know about respiratory symptoms.
And secondly, I want to know about
what I call constitutional symptoms.
Constitutional symptoms.
And these, this has nothing to do with the Constitution,
but it has to do with the body.
Kinda thinking about symptoms that affect the entire body.
So let me make a little bit of space on the canvas.
And we'll first start out thinking
about the respiratory side.
So respiratory symptoms, let me draw out
air coming into the body.
Remember, air has two major paths into your body,
it's gonna come in through your nose,
or it's gonna come in through your mouth, right?
And when it comes in, it's going to quickly join up.
Remember, air in the nose is gonna meet up
with air in the mouth, and it's gonna go down
through the windpipe, or the trachea we call it,
and it's gonna branch off into the
right and left lung.
So this is my right lung over here,
and on the other side we've got the left lung.
And remember the left lung is also gonna be
right next to the heart,
so we've gotta keep a little space for the heart.
So these are the two lungs,
and this is the air coming in.
Now if someone says that they have a stuffy nose,
that's a really common one, right?
They say they're congested,
or sometimes they might say a runny nose,
but any of these kinds of symptoms
you can think in your mind of this picture
and you can say, well yep,
this is right along the path
that air is gonna take on its way into the lungs.
So this is part of the respiratory track.
Now, another symptom might be a sore throat.
A sore throat.
And here again, you can see that
the air is actually gonna be passing
right through the throat
on its way down into the lungs.
And a really really common symptom,
you hear this all the time, is cough.
And whenever people talk about cough,
I just usually think about the lungs being involved there.
So these symptoms, stuffy nose, sore throat, cough,
you can think of this picture and really
can visualize the air going through,
and somehow these parts are being involved.
Now exactly what's happening
is that the virus is of course coming in, right?
It's being breathed in, that's how we take in the flu virus.
And as it hits these different areas,
the cells are getting damaged.
And that's what we experience
as a stuffy nose or a sore throat or a cough.
It's really damaged cells
that are being affected by the virus.
Now moving on to the other side,
the constitutional symptoms,
these are symptoms that I want you to think of
as affecting the whole body.
So if this is the whole body,
let's say these are the arms and the legs.
These are symptoms like fever.
Now if someone says they have fever,
it's very hard to point to one exact part of the body
that's affected, right?
You might say, well, I feel feverish,
really all over,
and if you're feeling feverish,
this face would be very sad like that.
So if you have symptoms like fevers,
and with fevers oftentimes you get chills as well.
I'm gonna put that together.
If you have fevers or chills,
that would be a constitutional symptom.
Another one would be something like bodyaches.
You know, if you are in bed
because your whole body is aching,
you wouldn't point to any one place,
you'd say, well it's just kind of all over.
And so that would be another constitutional symptom.
Another one that jumps to mind is fatigue.
Kinda the same idea.
Where your whole body is affected here.
So again, when someone tells me about flu,
I'm thinking that they better have
at least one of these respiratory symptoms
and at least one of these constitutional symptoms.
So I think of them in two categories, right?
And I want at least one from each category.
And they must have both
if they're gonna get me convinced
that they have the flu.
So scrolling up just a little bit,
just to make sure we don't forget.
It's gotta be abrupt, it's gotta happen
over the course of three to seven days,
and they should have at least one respiratory symptom
and at least one constitutional symptom.
Now this is good if I'm taking care of patients,
or I'm thinking about a clinical setting,
like the hospital or the emergency room.
But what about if you're doing research?
Well, it turns out that the Centers for Disease Control,
and they do a lot of research around influenza and flu,
they have a definition that I want you to know about.
Their definition, and you'll see this,
is that the person has to have a sore throat
or a cough, one or the other,
and I'll put a big or here.
And they have to have fevers.
So this is very similar to the definition I just gave you,
but this is the definition they use
when doing research, and when actually presenting data.
So it has to have these two things, right?
Sore throat or a cough, and fevers.
And so this is the definition for influenza-like illness.
Influenza-like illness.
And the short way of saying all this is ILI,
influenza-like illness.
So this again is the definition from the
Centers for Disease Control.
So if you ever hear ILI, at least now you know
what they're considering as being someone that has ILI.
So this brings up kind of an interesting question,
and that's why I kinda started out
by splitting things up between the illness and the virus.
I wanna go over to the virus side.
And just keep in the back of your mind
this idea of ILI.
Now on the virus side,
let me just kinda sketch out very quickly
in this green color,
what the influenza virus looks like.
I'm gonna label this influenza over here.
So this is my influenza virus,
and this little virus has got some RNA
on the inside of it,
so it's got RNA in here.
And I'm gonna draw out the RNA,
just so you can see it.
I'm gonna use two different colors,
so let's use like a purple color here,
and one important thing about this RNA
is that it's broken up into little pieces,
the way I'm drawing it here.
So it's got some purple chunks,
and let's draw some yellow chunks of RNA as well.
And this RNA of course is, as I said, genetic material,
so it's gonna be coding for proteins.
So you've got some proteins,
and let's say that you've got some
proteins out here on the surface.
And, you know, you could imagine that those
yellow proteins come from one of those yellow RNA segments,
and you've also got some purple proteins over here,
some purple proteins.
I'm gonna draw out some purple proteins here for you.
So let's say that the purple protein,
we can call that H,
and the yellow protein, we can call that N.
So what you're getting here is that you're seeing
a couple of the important parts of influenza virus.
And I just wanted you to start getting familiar
with the fact that it has, you know,
RNA on the inside that is broken up into chunks,
that it's got some surface proteins on the outside,
and a couple of those important ones,
we call them H and N for short.
And I'll tell you more about them in a future video.
So this is influenza virus,
and now the question is, if you have someone,
let's say I've got a friend or a family member
who tells me that they had an abrupt illness
that was six days, and they had fevers and a cough.
Well, it sounds like, based on what I said,
that this meets of course the CDC definiton
for influenza-like illness.
And so if I tested them,
let's say I actually, you know,
checked their nose with a little nose swab and did a test,
you would expect that I would actually find influenza there.
And most of the time, I would actually find influenza there.
But not always.
And this is actually an important concept.
That there are actually, believe it or not,
some of these little copycat viruses.
I'm gonna draw a couple copycat viruses here for you.
I'm gonna write out two of them.
There are actually more than two,
but we're just gonna talk about two of them.
And I'm not gonna draw them accurately,
this is just kind of a visual representation,
just to kind of show you what they are
and write up their names.
One is called rhinovirus.
Rhinovirus.
And you may be aware that rhino means nose,
and actually rhinovirus loves to infect the nose,
and that's actually why it's called rhinovirus.
And another copycat virus,
I'm gonna draw it looking a little different,
maybe a sideways looking thing, something like this.
This guy, this is RSV.
RSV.
And the full name of RSV is respiratory,
so you know it affects the lungs, syncytial virus.
Respiratory syncytial virus.
And we'll talk about that another time as well.
But the idea here guys,
is that these copycat viruses,
and this is interesting,
they can actually sometimes fool us
into thinking that we're dealing with influenza.
Because some of the symptoms you get with rhinovirus
and that you get with RSV
end up being pretty similiar
to the symptoms you get with the flu.
And so as a result, we have to have
some way of telling them apart.
And that's why, actually,
you may have heard of the term the cold.
Let me actually bring this down
and actually show you now
the cold and the flu side by side,
and how to kind of distinguish between the two.
So when you have, let's say the flu,
we said that usually you would have
some respiratory symptoms, check,
and you'd have some constitutional symptoms, check.
But if you have the cold, kinda the common cold, we call it,
then you generally only have respiratory symptoms.
You don't typically have fevers and chills
and body aches and fatigue.
You don't usually have that stuff with the cold.
So that's kinda the easy and quick way
to distinguish between the flu and the cold.
And those are the questions I always ask,
you know, patients of mine.
I say, well did you have body aches or fatigue?
And if the answers to all those kinds of questions are no,
I'm thinking aha, this person has the cold.
But of course, this isn't exact, right?
This isn't perfect in that once in a while,
people will actually fool you,
and they will actually have one of these copycat viruses,
the rhinovirus or RSV or adenovirus, or many other ones.
And they'll actually have influenza-like illness.
They'll actually have sore throat and fevers and body aches.
And so this is important to know,
that every single time we clinically think someone has,
you know, flu illness,
doesn't necessarily mean that they have the influenza virus.