Infectious Disease Epidemiology

Introduction
This series of lessons will introduce students to epidemiology through infectious diseases and the scientific methods epidemiologists use to investigate those diseases. Although these same methods are used to investigate other health issues (for example, chronic disease, environmental problems, behavioral problems, and injuries), these lessons focus on infectious disease to provide a clear example of epidemiology that is appropriate for students at the middle school level. For more information on the broad applications of epidemiology, see the "What is Epidemiology?" and "Why Teach Epidemiology?" sections below.

Each lesson in this module includes one or more activities. Each activity includes teacher background and student readings, or age-appropriate Internet links. All lessons align with national science and health standards, which are noted in each lesson.

This is a flexible resource package. You may use one or all of the lessons. However, it is recommended that you start with Lesson 1, Understanding the Epidemiologic Triangle through Infectious Diseases. This lesson introduces the content that students will apply in the remainder of the lessons.

There are two alternative culminating activities. Lesson 5, Scientific Poster Session, is appropriate for students of all ages. Lesson 6, Poisoned Picnic, will work better with older (seventh and eighth grades) or advanced students.

What is Epidemiology?
Epidemiology is the study of the distribution and determinants of health problems in specified populations and applying the learned information to control the health problems. It is the scientific method of problem solving used by "disease detectives"—epidemiologists, laboratory scientists, statisticians, physicians and other health care providers, and public health professionals—to get to the root of health problems in a community, whether the problem is a measles outbreak on a small college campus or a global influenza pandemic, an increase in homicide in a single community or a national surge in violence, or a localized or widespread rise in cancer.

Like investigators at the scene of a crime, disease detectives begin by looking for clues. They systematically gather information about what happened—Who is sick? What are their symptoms? When did they get sick? Where could they have been exposed to the illness? Using statistical analysis, investigators study the answers to these questions to find out how a particular health problem was introduced into a community.

Disease detectives then use what they have learned to prevent further illness. For example, when in 1993 more than 200 people in Washington State developed similar gastrointestinal symptoms, investigators traced the illnesses to undercooked hamburgers from a fast-food chain. Warnings to cook beef until it is no longer pink halted the outbreak and prevented further transmission.

Why Teach Epidemiology?
Epidemiology is an objective, scientific method of problem solving based on quantitative analysis. Teaching epidemiology

• improves students' reasoning and research skills,
• enhances their ability to analyze and solve complex problems, and
• sensitizes them to good health practices.

Ideas and Behaviors Common Among Students

• Students do not understand much about infectious diseases. In one study of middle and high school students in New York, over half showed almost no understanding of the biological concepts of virus, infection, and the immune system. When they were asked what a virus was, these students either characterized it as a "sickness," or provided specific examples (e.g., "stomach virus," "coughing virus") (Keselman and Patel, 2002).
• A 1953 study that is still cited by many authors showed that many elementary school students also believe that germs enter the body through the mouth while eating and leave the body through the mouth; every illness is caused by germs; all diseases are caused by the same kind of germ; the process of infection is automatic; any infection in the body necessarily makes it ill; and when medicine is administered, healing takes place immediately (Nagy, 1953).

References
Keselman and Patel. 2002. Sex, Myths, and Adolescents' Conceptual Understanding of HIV. Laboratory of Decision Making and Cognition, Department of Medical Informatics, Columbia University.

Nagy, M.H. (1953). The representations of "germs" by children. Journal of Genetic Psychology, 83, 227-240.