This document discusses the definitions and scope of epidemiology. It notes that epidemiology has expanded from initially focusing on infectious diseases and epidemics to also study chronic diseases, injuries, behaviors and more. The key definitions provided are: - Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to prevention and control of health problems. - It involves studying populations to describe disease frequency and patterns, identify risk factors and determinants, and apply findings to promote public health. - Epidemiology aims to describe, explain, predict and control diseases in populations.

2. Definitions of epidemiology
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 The scope of epidemiology has enlarged over years
 The definition of epidemiology has also changed from
narrow to modern concept, i.e.,
• ‘The branch of medical science dealing with epidemics’
(Parkin, 1873)
• ‘The science of the mass phenomena of infectious
diseases’ (Frost, 1927)
• ‘The study of disease, any disease, as a mass
phenomenon’ (Greenwood, 1934)
• ‘The study of the distribution and determinants of
disease frequency in man’ (MacMohan, 1960)

3. Definition
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“Epidemiology is the study of the Distribution
and determinants of Health Related states or
events in Specified Populations, and the
application of this study to the prevention and
control of health problems.”
(Last JM, Dictionary of Epidemiology, 1988:42).

4. Epidemiology….
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1) Study. Epidemiology is a scientific discipline - a
fundamental science of public health. It has, at its
foundation, sound methods of scientific inquiry.
Examples of studies include observational,
analytical or experimental.
2) Distribution. Frequency and pattern of health
events in a population. Frequency includes not only
the number of such events in a population, but also
the rate or risk of disease in the population.
Distribution by time, person and place could be
studied.

5. Epidemiology …
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3) Determinants. Epidemiology is also used to
search for causes and other factors that
influence the occurrence of health-related
events.
information on associated factors by comparing
groups with different rates of disease occurrence.
Identify demographic characteristics, genetic,
immunology, behaviors, environmental exposures,
and other potential factors associated with health
outcomes. Epidemiologic findings provide evidence
to organize effective public health measures (health
promotion, disease prevention and control)

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4) Health-related states or events. Originally,
epidemiology was concerned with epidemics of
communicable diseases. Then epidemiology was
extended to endemic communicable diseases and
non-communicable diseases.
More recently, epidemiologic methods have been
applied to chronic diseases, injuries, birth defects,
maternal and child health, occupational health and
environmental health.
Now, even behaviors related to health and
wellbeing (example: amount of exercise, seat belt
use) are studied using epidemiologic methods.

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5) Specified populations. Epidemiology studies
population groups with identifiable characteristics
such as occupational groups.

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6) Application. As a discipline within public
health, epidemiology provides data for directing
public health action. Epidemiological studies
provide evidences that are useful in promoting
and protecting health and controlling health
problems.

9. Goals of Epidemiology
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 To eliminate or reduce the health problems or
its consequences
 To promote the health and wellbeing of the
society as a whole

10. Aims of Epidemiology
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 describe, explain, predict and control
 Describe the health status of population –
enumerate the cases, obtain relative frequencies
of the disease within subgroups and to discover
trends in occurrence of disease
 Explain etiology of disease – discover causal
factors
 Predict the occurrence of disease – estimate
number of cases that will develop, identify
distribution within populations
 Control the distribution of disease – prevent
occurrence of new cases, treat existing cases
and prolong life of those with the disease

11. Scope and uses of epidemiology
 Studying causation of disease: Genetic, behavioral
and environmental causes
 Course and outcome of disease (natural history of
disease): How a disease progresses through
subclinical changes, clinical disease and recovery,
disability or death
 Describing health status of populations: Describing the
burden of disease so that limited resources could be
used in best possible ways.
 Evaluating interventions: Interventions include health
promotion, preventive measures, treatment and
behavior change. These interventions aim at reducing
ill health in populations and thus improving public
health.
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12.  Epidemiology studies specific population
selected from a specific area at a specific time.
Example – patients working in a factory or
children having pneumonia in a certain
community. The specific population form base for
defining subgroups (education, age, ethnicity etc)
 Epidemiology is concerned not only with death,
illness and disability but also with behaviors
affecting health
Scope and uses of epidemiology
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13. Methodology of epidemiological study
 Definition of the problem, such as relationship of
outcome and exposure
 Statement of existing factors by tabulating all
available information as per age, sex, class, etc.
 Formulation of hypothesis, e.g. smoking
increases risk of cancer
 Testing of hypothesis by making observations,
trials or investigations
 Statistical analysis and drawing of logical
conclusions
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14.  Agent, host and environment
 Global, regional and national context
 Prevention and control programs and
status
 National policy and strategies
 Targets and achievement
 Critical reflections
Applied epidemiology
1. Presentation and discussion
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15.  Understand organization and content of
papers published in journals
 Develop protocol for carrying out an
epidemiological study
 Update advances in epidemiological
concepts and methods
2. Critical appraisal of scientific papers
and application of epidemiological
methods to study health problems
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16. 3. Analyze data set to calculate
epidemiological indices
4. Study of organization of health
services for various health problems
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17. Thanks
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