Download Understanding Epidemiology

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:
1) Experimental – epidemiologist has control
over the assignment of treatment and
control groups from the start.
o
Example: Clinical trials for new pharmaceuticals.
2) Observational – epidemiologist has no
control over the assignment of treatment
and control groups from the start.
Observational Studies

Two types:
1) Descriptive (Person, Place, and Time)
o Collect information to characterize and
summarize the health event or problem.
o Most basic and fundamental to epidemiologists.
2) Analytical (How and Why)
o 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