1. The Epidemiologic Triangle
Switch gears: really bring in society this time with epidemiology
Contagion Trailer:
After: What did they say about how often we touch our face? Why do you think this might be important? Why do they show images of cars, bridges, planes, etc.?
Contagion

2. Epidemiology 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 is literally defined as “the study of that which befalls people”

3. Epidemiology
Epidemiology – learning how diseases are distributed in a certain place and time
Your homework this week is an epidemiological study
How?
You will look at most common diseases amongst your age group (you)
You will look at most diseases other members of your family might have gotten
From this information, we should be able to draw conclusions as a class about why certain diseases appear in certain populations at particular times

4. 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”)
The center of the triangle is TIME – this is what epidemiologists are working against
HOST
TIME
Agent: The agent is the cause of the disease. When studying the epidemiology of most infectious diseases, the agent is a microbe—an organism too small to be seen with the naked eye. Disease-causing microbes are bacteria, virus, fungi, and protozoa (a type of parasite). They are what most people call “germs.” Bacteria, fungi, viruses, parasites
Host: Hosts are organisms, usually humans or animals, which are exposed to and harbor a disease. The host can be the organism that gets sick, as well as any animal carrier (including insects and worms) that may or may not get sick. Although the host may or may not know it has the disease or have any outward signs of illness, the disease does take lodging from the host. The “host” heading also includes symptoms of the disease. Different people may have different reactions to the same agent. For example, adults infected with the virus varicella (chickenpox) are more likely than children to develop serious complications.
Environment: The environment is the favorable surroundings and conditions external to the host that cause or allow the disease to be transmitted. Some diseases live best in dirty water. Others survive in human blood. Still others, like E. coli, thrive in warm temperatures but are killed by high heat. Other environment factors include the season of the year (in the U.S., the peak of the flu season is between November and March, for example).
AGENT
ENVIRONMENT

5. 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
How does an epidemic reinforce OR challenge the American ideal that “all men are created equal”?

6. 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
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
Varicella zoster, a virus
AGENT
ENVIRONMENT

7. 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)
Share out student observations as a class

8. Mystery Solved! Let’s see if you were right… Mystery Solved
Review agent, host, environment with class

9. 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!
In your skit, include…
The epidemiological triangle for
how your disease is transmitted,
including time
-What people should do
avoid getting disease
TIME
HOST
ENVIRONMENT
AGENT
Resources: CDC, NIH
Use Cardstock info
Extensions/Alternative Activities: A news story, Eggs with agent/host/environment that students must identify each component; a radio broadcast;

10. 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?
Do activity with teachers