1. The Epidemiologic Triangle Contagion

2. 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, epidemiologyliterally translates to “the study of that which befalls people” • Epidemiology – learning how diseases are distributed in a certain place and time

3. 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?

4. John Snow: The First Epidemiologist • Read “John Snow’s Methods” • How did John Snow prove that cholera was being spread by contaminated water?

5. 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”) HOST The center of the triangle is TIME – this is what epidemiologists are working against TIME AGENT ENVIRONMENT

6. Outbreaks, Epidemic vs. Endemic • An outbreakor 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 • Endemicmeans a population has a high level of disease all the time. • Example: Malaria is endemic in Africa

7. Example Case Study: Varicella zoster (chickenpox) HOST 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 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

8. 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)

9. Mystery Solved! • Let’s see if you were right… Mystery Solved

10. 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 HOST TIME AGENT ENVIRONMENT

11. Common Infectious Diseases (HW or Classroom Activity) 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?