all right I want to turn to disease
prevention because I've already told you
this is real important but then the
question is what is it when we mean what
do we mean by disease prevention here's
a definition anticipatory action so
action taken in advance to reduce the
possibility of an event or condition
occurring or developing or to minimize
the damage that may result from the
event or condition if it does occur
that's a lot of blather a lot of words
let's see if we can make some sense out
of it schematically here primary
prevention is the column that I'm
pointing to right here that's the kind
of prevention we in public health love
that's Big Time Public Health what is it
doing it's dealing with people who are
susceptible to a disease problem but
don't have the problem at all so it's
say going to kids who could get obese if
they don't exercise and watch their
diets and it's intervening with them to
make sure that they avoid becoming obese
and having the health problems
associated with it down the line there
will be a reduced incidence of disease
as a consequence we love primary
prevention primary prevention is the
core the heart of Public Health there's
another piece of it that we do I should
I should mention probably the most
important single most important example
of that is immunizations people who are
getting immunized against diseases don't
have the diseases you give them the
immunization they don't get the disease
so you're preventing it from occurring
in the first place it's wonderful
because there's no adverse consequences
now obviously with immunizations there
are very occasional adverse consequences
all right there's another area though
that we like to we like this a lot I
don't like it as much as primary but we
like secondary to secondary is good
secondaries taking people are
asymptomatic and it is doing something
by way of an intervention typically
screening and treatment that will end up
reduce
the prevalence or consequence of their
asymptomatic problem what's a good
example of that sir
breast cancer screening absolutely good
other examples here yeah
diabetes is a very good one high blood
pressure high cholesterol obesity there
are all kinds of things that we can
screen for and do something about even
though there's a problem there you can
avoid the problem down the line first
time ever went to give blood I was a
senior in college and I was probably
nervous I don't I didn't feel like it
but I came out of there and he said oh
you've got borderline high blood
pressure now it turns out both of my
parents have had you know had baha'i
blood pressure throughout their lives
and lo and behold I started getting
treated for it now one thing you can do
of course is you can intervene by
telling people to lose weight to
exercise get themselves in better shape
and maybe their blood pressure will drop
without giving a medication but that
doesn't work the next line of defense is
medication and when that happens we have
very good evidence that that will reduce
the prevalence of strokes heart disease
and other things down the line now
tertiary prevention means you're
symptomatic you've got a problem and you
know it and what we're going to do is
we're going to intervene to try to
reduce the complications and disability
from that condition this is what we
commonly do in medical care and what we
commonly refer to as treatment disease
condition something symptomatic that you
come in to the doctor about and they say
we're going to do X Y & Z and try to
reduce the problems associated with it
so from a technical point of view excuse
me a technical point of view we got
primary secondary and tertiary but in
practice public health is much more
narrowly focused on primary and
secondary tertiary is where we talk
about services that are provided in the
other health services yes ma'am
STD treatment once again they actually
this is interesting that so many of you
are raising us STD treatment will
be something it could be asymptomatic it
could be symptomatic it depends I mean
it depends where you are with the
condition if it's asymptomatic you can
get treated typically with an antibiotic
and avoid the consequences of it if it's
already symptomatic so if something's
happening to you once again treatment
may be able to reduce the adverse
consequences of it okay
what I thought was interesting when you
mention STDs that's another case of what
we refer to as externalities where a big
part of the problem is not just you
having it but the fact that you're
likely to spread the disease to others
and we'll be talking more about that
later
sir the big difference between incidence
and prevalence and again I think the
epital actual probably deal with
incidents are new cases that are
occurring in a given period of time
prevalence are the number of existing
cases so you can think of the prevalence
of high blood pressure as the proportion
of the population at any given time who
have high blood pressure
the incidence would be the number of new
cases during that period like a year
that are identified okay very important
distinction has a lot of effect on how
you think about dealing with disease by
the way okay example of the different
levels of prevention I think these I
hope will help to clarify this think
about motor vehicle injuries primary one
of the best things we've ever done and
we've done lots and the automotive
safety area that involves the structure
of the roads putting in median dividers
so you divide the highways has
dramatically reduce the number of
collisions I don't know I think I
mentioned this earlier well I'll ask and
if nobody knows then either I didn't
mention it or nobody was listening
what's the most dangerous driving
condition did I mention this why pardon
no no no I'm noting about texting but
assuming you're driving responsibly
you're awake you're not drinking you're
not eating you're not doing your
eyelashes or whatever okay what's the
most drained dangerous kind of roads to
be driving on in what conditions sir
nope pardon twisty roads in the rain
might be pretty bad yeah depending but
there's a specific kind you've done it
huh you've been there specific kind of
road and what I'm thinking about I guess
I didn't mention it before it's too late
roads typically in non urban areas at
dusk so the Sun is going down it's going
to be very bright in one direction it
may be a little difficult to see and and
so on you have cars coming at relatively
advanced speeds with no divider between
them that's the most dangerous condition
for driving cars divided highways got
rid of that that's primary prevention
those collisions don't occur we came up
with them and and again when you think
about do you think about coming up with
divided highways as Public Health I
don't think I ever would have thought of
it that way originally that's great
Public Health you're gonna see some data
on the reduction in automobile collision
injuries that will blow you away and
it's terrific Public Health and a lot of
it has to do with the structure of the
highways and the structure of the cars
and not much do with the individuals
inside of them secondary prevention
requiring safer cars so airbags
somebody's in a collision so the event
has occurred the airbag is dramatically
reducing their risk of serious injury or
in some cases of any consequential
injury at all better driving practices
like wearing seatbelts also does that
tertiary is the emergency medical
service system we save a lot of lives
after car collisions because we have
systems to get to people quickly where
we can also provide them life-saving
services on the spot we don't have to
get them to the hospital which used to
be a case an ambulance used to be
something you were thrown in and they
would try and drive you to a high
spittle and hope they got you there fast
enough now emergency services vehicles
will provide treatment on-site and you
save many more lives as a consequence of
it all right how about high blood
pressure primary prevention is dietary
education and exercise if we all did
what we should in those departments we'd
have a lot less high blood pressure but
we'd have some and that gets to
secondary that's where you screen for
high blood pressure and treat with
medications tertiary we treat for the
diseases that occur strokes heart
disease and so on any questions about
the distinctions among primary secondary
and tertiary and I will say a couple of
you have given some good examples it's
not always unambiguously clear which
label is best for one of these but I
hope you understand the general
principles here all right I'm not gonna
spend a lot of time on this because I
actually have three or four slides and
don't want to take too much time with it
this is a very traditional model within
epidemiology and public health it's
traditionally an infectious disease
model the notion that for a disease to
occur you have to have three things an
agent a host and an environment that
supports it that's kind of an important
concept it's not simply there's a bug
out there that bug has to have a host
and an environment to make the disease
come into being so think of this with
regard to malaria the agent etiologic
agent is Plasmodium that's the bug the
host is human beings and the environment
includes mosquitoes swamps and the like
that breed mosquitoes where the
mosquitoes pick up the Plasmodium and
then deliver it to the human being okay
more recently some people have started
to adapt the idea of this triangle to
behavior related issues these aren't
infectious diseases in the traditional
fashion but they have a kind of
communicability element to them so in
the case of tobacco the agent is the
tobacco product the host is somebody
who's a smoker or chewer
and there are incidental hosts who are
in
voluntary smokers people around smokers
and an environment where you have family
friends culture media politics etc all
encouraging smoking and the vector in
this case would be the tobacco product
manufacturers so this is just a way to
think about something that's not
strictly an infectious disease that has
has these same qualities that requires
these things to come together to have a
disease problem