Transcript The Sociology of Infectious Disease: Using Middle School

The
Epidemiologic
Triangle
Contagion
Epidemiology: What is it?
• Epi – means “on, upon, befall” (ex: epidermis)
• Demo – means “people” (ex: demographics, the
study of populations)
• -ology – means “the study of”(ex: biology, geology)
• So, epidemiology literally translates to “the study
of that which befalls people”
• Epidemiology – learning how diseases are
distributed in a certain place and time
John Snow: The First Epidemiologist
• Read “Finding the Real Cause of Cholera” with
your table.
• What did John Snow think was causing the
cholera outbreak?
• How do you think John Snow proved his theory
using the scientific method?
John Snow: The First Epidemiologist
• Read “John
Snow’s
Methods”
– How did John
Snow prove
that cholera
was being
spread by
contaminated
water?
Epidemiology
• The Center for Disease Control (CDC) uses a
model called the Epidemiologic Triangle to
pinpoint outbreaks of infectious diseases
The triangle has three vertices:
• Agent, or microbe that
causes the disease (the
“What” of the triangle
• Host, or organism harboring
the disease (the “who” of
the triangle)
• Environment, or those
external factors that cause
or allow disease
transmission (the “where”)
AGENT
HOST
The center of the
triangle is TIME –
this is what
epidemiologists are
working against
TIME
ENVIRONMENT
Outbreaks, Epidemic vs. Endemic
• An outbreak or epidemic exists when there are
more cases of a particular disease than
expected in a given area, or among a specific
group of people, over a particular time.
– Example: Seasonal flu
• Endemic means a population has a high level
of disease all the time.
– Example: Malaria is endemic in Africa
Example Case Study: Varicella zoster
(chickenpox)
People under 15 most at risk
Anyone who hasn’t had it is
susceptible
Can remain in the body and
cause shingles (painful blisters)
in adults
Varicella
zoster, a
virus
AGENT
HOST
Transmitted from
an infected
person through
coughs or
sneezes, or from
contact with the
fluid from
chickenpox
blisters
Most commonly
transmitted in
the early winter
or spring, when
temperatures are
moderate
ENVIRONMENT
Mystery Disease
• Watch the following clip: Mystery Disease
• While watching, look for the following
epidemiological clues:
– How might it be spreading? (Agent)
– Who/what is getting disease? (Host)
– Where is it happening? (Environment)
Mystery Solved!
• Let’s see if you were right… Mystery Solved
Public Service Announcement Skits
• Working in your table groups, use the information
from the case study provided to create a Public
Service Announcement skit about your disease.
• It can be a radio broadcast, TV commercial, talk
show interview, etc… be creative!
HOST
• In your skit, include…
– The epidemiological triangle for
how your disease is transmitted,
including time
-What people should do
AGENT
avoid getting disease
TIME
ENVIRONMENT
Common Infectious Diseases (HW or
Classroom Activity)
I’ve Had
Family Members Have
Had
Heard About
Compare the diseases you’ve had, and diseases your family
has had with your table. What diseases do you have in
common? What diseases did your family have that you
haven’t had? Why do you think this is? What are some
diseases you’ve heard about, but don’t know anyone who
has had that disease?