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Prevalence vs Incidence Understanding Covid Numbers - YouTube
Channel: NurseMinder
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Have you guys been noticing that when
they report the numbers of
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covid on a daily basis that there's also
this like
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overarching number that seems to be a
whole lot bigger
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so for example they might report that
there's only 29 active cases in one
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place
but there's over 300 per 100
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000 also identified so how do we get to
those numbers?
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Well this is known as incidence versus
prevalence and
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what we're getting on a daily basis
right now with our covid pandemic
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is a lesson in epidemiology when it
comes to reporting numbers based on
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incidence and prevalence. So we're going
to talk about those two factors
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in this video, break down those numbers
so they make sense to you
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right after this.
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Welcome back my name is Tammy and this
is NurseMinder and on this channel we do
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everything nursing so if you're new here
consider subscribing below so that you
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get the next video when it's released.
Now before we head to the board so I can
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kind of detail this up for you in
pictures, I'm a visual learner I like to
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see things,
we're going to just first basically
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define incidence and prevalence. So
incidence is
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the number of new cases PER a defined
set of population over a determined amount
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of time.
So the new cases we hear those every
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night, we had 157 new cases we had 86 new
cases overnight.
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That is one piece of information we need
to identify
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what the incident rate is. Now prevalence
is really a factor of how many people
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have it currently within the population
overall. So let's go to the board and
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just kind of look at those two things in
more detail.
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Now when it comes to incident rates
we're looking at how many new cases per
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a defined population and
what that means in defined population is
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that everybody who belongs
in this category needs to have the
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potential
to become at risk or to move into a
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diagnosis
of whatever it is you're measuring. So in
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this lesson we'll talk about covid but
this could be tuberculosis, this could be
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heart attacks, so if you were looking at
heart attacks for example,
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you would get rid of everybody who's
under the age of 18 and maybe even under
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the age of 30
and then that would reduce the
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population size because
four-year-olds don't have heart attacks.
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All right so in this case because it's
covid everybody is at risk we've had
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no data that comes out to show that
children are not at risk,
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there's no difference between gender so
far male and women are affected,
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there's no ethnicity immunity
based on where you live and where you
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were born so
everyone's at risk so the entire
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population is in
this defined set. So from here let's just
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say
this person this person and this person
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become infected,
we now have three new cases
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in our population size of 10.
So in order to create the risk factor so
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say all of a sudden we had a mass group
of people move into our community
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and our community now is a thousand
people we're going to multiply that by
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1000
and that tells me that I have a
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potential 300 people that will
move from our defined population into
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our
new cases. So there's a risk that we can
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identify and then we can
plan to implement strategies to manage
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the risk,
just like we did with covid by making
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sure we had enough staff and icu beds
and ventilators.
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That was part of the planning based on
the risk that was assigned to it
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and then we can also plan education,
prevention, such as our swabbing and
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vaccinations
to meet the demand.
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Let's just take these 10 people over
here and let's just assume
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or let's pretend for example's sake that
they have decided
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or they've come out with information
that says anybody under the age of 10
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is immune. We've never seen a case
doesn't matter what we do
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they just don't seem to get covid. So
we're going to say that these two people
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here
are under the age of 10 so they no
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longer count in our population base.
They're not part of our defined
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population anymore. so now I have a base
population of only eight
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people who are at risk of getting
covid and moving into the
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diagnosed cases. So we now have eight
as our base population instead of ten
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with that we're gonna say three people
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become infected
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so three out of eight will become
affected if we multiply again by a
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population size of a thousand
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the incident rate the risk rate goes
from
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300 now to 375.
The risk factor has increased because
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the population size has
decreased. All right so on September 7th
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we have a 157 new cases in alberta so
that's that new cases
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for incidents what's the total
population that's at risk in alberta is
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4.428
million people. Now when we're talking
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about this big of a number
we'd like to break it down into per 100
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000 people so when you do the math
157 divided by 4.428 million
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times by 100 000 people you have an
incident rate
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of 3.5 people for every 100
000 in the province of Alberta
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but as we know there are places that
have higher incident rates
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than others, some have zero cases
some have hundreds of cases, so being
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selective about the population that
you're choosing for the area that you
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live
understanding how many new cases will
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tell you what the risk level is to
getting
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that illness or disease. Now let's look
at prevalence.
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Now prevalence is different in the sense
that it's looking at the number of
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affected people,
so this will include new cases but it
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will also include the cases that were
diagnosed yesterday where the person
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hasn't recovered,
10 days ago if the person hasn't
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recovered, and so this number will be
higher
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and it is over the total population not
just that defined
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subset all right. So let's look at covid
numbers and look at prevalence
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because this is what we often see
in our map on line when we google those
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numbers.
Here we have an example of Vulcan county
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this is September 7th here in Alberta.
Note that they have a rate of active
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cases per 100 000 and that is at 313
people. They only have 29 active cases
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and the population size is only 9 245 so
what do these numbers
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really tell us? So we come back and look
at prevalence,
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remember prevalence is the number of
people affected, and in that case it was
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29 cases - that's how many active cases
they currently have
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right now, so remember active is new
cases plus those who have been diagnosed
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before,
over the total population, and their
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population
was 9 245. So if we do
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this math 29 divided by 9 245 and
multiply that by 100 000 to represent
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the prevalence per 100 000 people should
that many people live in that country we
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would
earn that county, we would see they have
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313
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per 100 000. This again helps to provide
information for planning
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and to make sure that people are
accessing the resources that they need.
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But this doesn't tell the whole story.
Remember that this is the number
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affected and people can move in and out
of this category
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by recovery or death and we know that
there are people who are dying
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from covid and same thing with this
total population
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this can change with births and deaths.
So that number is fluid as well.
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So that is our lesson on incidence and
prevalence, now when you're hearing the
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nightly news you can go okay we have 157
new cases
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but that's out of how many? and what does
that look like for risk?
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what is my actual potential risk if I
was in a room of 100 people?
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and of course prevalence looking to see
where we're at currently with this
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illness
and that will help you to understand why
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the planning is in place
and why certain measures have been taken
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to reduce the risk
and to navigate the health challenges
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that people are going to be coming up
against.
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Don't forget to comment below let me
know what you've learned out about your
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incidence and prevalence rate
where you live. Is it as bad as where
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I've just shared or is it better?
let me know below. Until next time make
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it a great day.
Hey I know you're probably not ready to
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get off your phone or go back to work
just yet or maybe even turn the lights
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off to go to sleep,
so why don't you spend a little bit more
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time here watching another video ;)
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