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EPIDEMIOLOGY
 Epidemiology
 Epi:
(epi/dem/o/logy) comes from
meaning “on or upon”
 Demos:
 Ology:
meaning “people”
meaning “the study of”
 Epidemiology
is the study of the distribution and
determination of the causes of health-related conditions
or events in populations. It is used in healthcare and
especially with infectious disease.
EPIDEMIOLOGY
HOW EPIDEMIOLOGY IS USED

These questions are researched when doing a community assessment:

What are the actual and potential health problems in the community?

Where do they occur?

Who is at risk?

Which problems are declining over time?

Which ones are increasing or have the potential to increase?

How do these patterns relate to the level and distribution of services
available?
COMMUNITY HEALTH ASSESSMENT
 Case
Definition
A
set of standard criteria for deciding whether a
person has a particular disease or other healthrelated condition
THE EPIDEMIOLOGIC APPROACH
 When
physicians diagnose a case of a reportable
disease they send a report of the case to their local
health department.
 Time
- when the case occurred
 Place
- where the patient lived
 Person
- the age, race, and sex of the patient
STATISTICS AND REPORTS
 Health
departments convert the case counts into
rates, which relate the number of cases to the size of
the population where they occurred
STATISTICS AND REPORTS
TYPES OF EPIDEMIOLOGY
 Organize
person
 Time
and summarize data according to time, place, and
– disease rates change over time
 Example:
the seasonal increase in influenza with the
onset of cold weather
 Time
data is usually shown on a graph
DESCRIPTIVE EPIDEMIOLOGY
 Place
- describe a health event by place to gain insight into the
geographical extent of the problem and similarities in location.
 Residence
 Birthplace
 Place
of employment
 School
district
 Hospital
unit
DESCRIPTIVE EPIDEMIOLOGY


Person:

inherent characteristics of people

Age

Race

Sex
Acquired Characteristics

Immunity

Marital status
DESCRIPTIVE EPIDEMIOLOGY
 Activities
 Occupation
 Leisure
 Use
activities
of medications/tobacco/drugs
DESCRIPTIVE EPIDEMIOLOGY
 Conditions
in which people live
 Socioeconomic
 Access
status
to medical care
DESCRIPTIVE EPIDEMIOLOGY
 Used
to search for causes and effects, or the why and
the how.
 Looks
for relationships in the data
ANALYTIC EPIDEMIOLOGY
CAUSATION
 Cause
of disease is a factor (characteristic, behavior,
event, etc.) that influences the occurrence of disease.
 An
increase in the factors leads to an increase in
disease.
 Reduction
disease
of the factors leads to a reduction in
CAUSATION
EPIDEMIOLOGIC
TRIANGLE
Traditional model of
infectious disease
causation.
EPIDEMIOLOGIST USE
THE CHAIN OF INFECTION

Level of Disease - amount of a particular disease that is
usually present in a community





Increasing amount of disease
Sporadic
Endemic
Epidemic
Pandemic
EPIDEMIOLOGY: LEVEL OF DISEASE

Sporadic - irregular pattern of occurrence, with occasional cases
occurring at irregular intervals

Endemic - persistent level of occurrence with a low to moderate
disease level

Epidemic or Outbreak- occurrence of a disease within an area is
clearly in excess of the expected level for a given time period


Example: Ebola epidemic or outbreak of 2014
Pandemic - an epidemic spreads over several countries or continents,
affecting a large number of people

Example: Bubonic plague and AIDS
EPIDEMIOLOGY: LEVEL OF DISEASE