Hello, my name is Dr. Raywat
Deonandan and thank you for watching
my videos on infectious
disease pandemic epidemiology.
In this video, we'll learn how to
define epidemic and pandemic.
We'll look at the different kinds of epidemics,
some of the famous epidemics
going back throughout history,
going back hundreds of years.
We'll look at some of the methods
of transmission of these diseases.
And finally we'll go over some of
the ways we can control transmission.
I hope you enjoy them.
With this course, we hope that you'll
have a few objectives for your learning.
First, you're going to know how outbreaks,
epidemics and pandemics are defined
and how you can classify epidemics according
to how they spread through a population.
You're going to be able to name at least one
pandemic in each of the following time periods:
the 1900s, The 1800s and after 2000.
you're going to learn a
lot about zoonotic diseases
and be able to name one
from the following categories:
bacteria, viruses, fungi and parasites.
And you want to learn about
some of the important indicators
for describing epidemics and
pandemics particularly the CFR,
the case fatality rate and the
IFR, the infection fatality rate.
You're going to be able to calculate
some of the important indicators as well,
such as the primary and secondary attack rate.
And you're going to do so by
looking at some original data.
You're going to learn about some
other important monitoring indicators,
Things like the R-nought, the basic
reproduction number, herd immunity
and how we calculate the herd
immunity threshold from the R-nought.
You're also going to learn how
the effective reproduction number R,
Or R sub e is different from R-nought.
You're going to compute
R-nought from original data
and you're going to know what factors
affect its value and how to use this indicator
to predict the evolution of an epidemic.
I'm going to show you how to draw the
graphs of two diseases with the same R-nought
but one being more infectious over a short
period of time and the other being less infectious.
And how, using that graphical technique can
help us understand how the disease is spreading.
You're going to learn how to interpret
various types of epidemic curves
and even be able to construct
one from your own data.
And you're going to identify the main
components of a disease transmission cycle.
And using that information, be able
to devise infection control methods
for interrupting that cycle.
We're going to learn a little bit about
some of the infectious disease models,
like the SIR/SEIR and the basic
assumptions and faults that underlie all models.
And lastly, we're going to talk about the major
challenges of the pandemic of the day, COVID-19.
So let's start with defining some terms.
First is 'outbreak'.
What's an outbreak?
You've heard this term.
Public health officials
always talk about outbreaks.
An outbreak is an increase, often a sudden
increase in the number of cases of a disease
above what is normally expected in
that population in that particular area.
Now what is normally expected is
going to vary from place to place,
and different people are going
to have different thresholds.
So it's very much a qualitative distinction.
But we use the word outbreak to describe
a sudden appearance of the disease.
An epidemic is a lot like an outbreak,
But we usually use that word to define
outbreaks affecting many
people over a wider area.
Again, it's a more qualitative distinction
between the two.
And lastly pandemic, that's the big one.
That's an epidemic that spread over several
countries or continents or official WHO regions
and that affects a large
percentage of the population.
Pandemic is typically worldwide.
So, outbreak is the smallest
type of disease manifestation.
Epidemic is the medium type, and
of course pandemic is the largest one.
It's important to realize that these distinctions do
not are not based on the severity of the disease,
but just on the degree to which it's spreading.
So the official definition of an
epidemic from the CDC, is that
epidemics occur when an agent and susceptible
hosts are present in adequate numbers
and the agent can be effectively conveyed
from a source to the susceptible hosts.
Okay, what did I just describe there?
I described an infectious disease.
An agent is the disease, the pathogen.
The hosts are the people who become infected,
and the agent is being conveyed
between the source to hosts.
What I described there is
the spread of an epidemic.