Understanding Epidemiology Introduction to Epidemiology and Epidemiological Concepts
What is Epidemiology? • The word “epidemiology” comes from three Greek words: • Epi = “on, upon, or befalls.” • Demo = “people.” • -ology = “the study of.” • So, epidemiology can be literally defined as “the study of that which befalls people.”
What is Epidemiology in terms of Public Health? • “The study of the distribution and determinants of health-related states in specified populations, and the application of this study to control health problems.” • It is the basic science of public health.
Why Learn about Epidemiology? • Epidemiology provides an objective, scientific method of problem solving. • Benefits to students include: • Improved reasoning and research skills. • Enhance ability to analyze and solve complex problems. • Provides a foundation for the concept of positive health practices.
Epidemiology vs. Medicine Epidemiology: • Concerned with the population as a whole. • Uses information to generate hypotheses between exposure and disease. • Tests hypotheses using analytical studies. • Recommends community intervention to end health problem. Medicine: • Concerned with the individual person (or patient). • Uses information to make a diagnosis. • Tests diagnosis by conducting additional diagnostic tests. • Recommends a prescribed medical treatment to end health problem.
Epidemiological Triangle • A model that helps epidemiologists (and other scientists) study various health problems. • Specific to epidemiology, this model depicts the interaction and interdependence of the agent, host, and environment on the spread of diseases. • Very useful when studying infectious diseases.
Epidemiological Triangle • Agent • The “what” – what caused the disease. • Host • The “who” – who harbors the disease; usually includes a list of symptoms among those affected. • Environment • The “where” – favorable conditions external to the host that allow for transmission.
Epidemiological Triangle EPIDEMIOLOGY’S GOAL = to “break” the chain of at least one side of the triangle to disrupt or stop the continuation of the disease.
Epidemiological Studies • Include both a treatment group and a control group. • Two types: • Experimental – epidemiologist has control over the assignment of treatment and control groups from the start. • Example: Clinical trials for new pharmaceuticals. • Observational – epidemiologist has no control over the assignment of treatment and control groups from the start.
Observational Studies • Two types: • Descriptive (Person, Place, and Time) • Collect information to characterize and summarize the health event or problem. • Most basic and fundamental to epidemiologists. • Analytical (How and Why) • Relies on comparisons between groups to determine the role of various risk factors in causing the problem.
Epidemiological Surveillance • Defined as “the ongoing, systematic collection, analysis, and interpretation of outcome specific health data, closely integrated with the timely dissemination of these data to those responsible for preventing and controlling disease.”
Types of Surveillance • Active • Initiated by a health department. • Solicit reports from various health providers. • Passive • Initiated by the source of the data. • Utilizes practices already occurring among healthcare workers in the professional setting (i.e, reportable disease forms).
Epidemiological Uses of Surveillance • Help predict epidemics or pandemics. • Facilitates planning in terms of developing prevention strategies and interventions. • Aids in hypothesis generating by inferring “cause and effect” relationships. • Allows one to study the natural history of a disease and note: • Changes in the disease-causing organism of agent. • Changes in health practices among people.
Resources • Center for Disease Control and Prevention (CDC). Excite: Epidemiology in the Classroom. “An Introduction to Epidemiology.” http://www.cdc.gov/excite/classroom/intro_epi.htm. • Center for Disease Control and Prevention (CDC). Bam!: Body and Mind. “Understanding the Epidemiological Triangle through Infectious Diseases” http://www.bam.gov/teachers/activities/epi_1_triangle.pdf. • Centers for Disease Control and Prevention (CDC). “BAM! Teacher’s Corner: Infectious Disease Epidemiology.” http://www.bam.gov/teachers/epidemiology.html