the epidemiologic triangle
DESCRIPTION
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) - PowerPoint PPT PresentationTRANSCRIPT
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
TIME
HOST
ENVIRONMENTAGENT
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
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)
HOST
ENVIRONMENTAGENT
Varicella zoster, a virus
People under 15 most at riskAnyone who hasn’t had it is susceptibleCan remain in the body and cause shingles (painful blisters) in adults
Transmitted from an infected person through coughs or sneezes, or from contact with the fluid from chickenpox blistersMost commonly transmitted in the early winter or spring, when temperatures are moderate
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!
• In your skit, include…– The epidemiological triangle for how your disease is transmitted, including time-What people should doavoid getting disease
TIME
HOST
ENVIRONMENTAGENT
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?