Epidemiology is the study of disease distribution and determinants within populations. It involves observing people in their natural environments to study risk factors for disease development and control health problems. The field aims to describe disease distribution and causes, identify disease pathogenesis factors, and provide data to prevent, control, and treat disease. Epidemiology considers the interaction between agents, hosts, and the environment (the epidemiological triad) in disease transmission and occurrence.

1. REPRESENTED BY WASIM AKRAM
BSC NURSING
ADWIKA INSTITUTE OF NURSING

2. CONTENTS
 INTRODUCTION
 MEANING
 HISTROLOGICAL BACKGROUND
 DEFINITION
 AIMS
 Communicable and Noncommunicable Diseases
 EPIDEMIOLOGICAL TRIAD
 CLASSIFICATION
 SUMMARY

3. • Epidemiology is the study of the
distribution and determinants of diseases
within human populations.
• Research in this field is based primarily
upon observing people directly in their
natural environment.
• Epidemiology can be used for analytic
purposes , such as studying risk factors for
disease development.

4. MEANING OF EPIDEMIOLOGY
The word “epidemiology” is derieved from
“epidemic” which is very old word dating
back to the 3rd century. Literary the word
“epidemiology” is the combination of three
Greek words:
Epi :- Among
Demos:- People
Logos:- Study of science
It means epidemiology is the study of
events that occur among people.

5. . The Greek physician Hippocrates, traditionally
regarded as the father of medicine was one of the
initial major contributors of development of
epidemiology .
.Hippocrates had explained the disease
occurrence with rational his book on “Epidemics”
and on “air, water and places”.
. Hippocrates described disease as a mass
phenomenon affecting individuals.

6. There are many definitions of epidemiology but the main
components of the definition are same which includes.
Study of the frequency of the disease
Study of the distribution of disease
 Study of the causes of disease
Study of the distribution and determinants of health
related states or events in specified population, and the
application of this study to the control of health problems .
JOHAN M LAST 1988
Epidemiology is the study of occurrence, causes
and distribution of infectious diseases it occurs in
humans. - Historical approach

7. The international epidemiology association (IEA) has laid
down three main aims:
• The describe the distribution and magnitude of health
and disease problems among individuals and groups.1
•To identify etiological factors in the pathogenesis of
disease.
•To provide data for planning implementation and
evaluation of services for the prevention , control and
treatment of disease.
•To eliminate or reduce the health problems and
complication of the health problem.
•To promote the health and well-being of the community as
a whole.

8. COMMUNICABLE AND NON
COMMUNICABLE DISEASES
The epidemiological difference between communicable and
non-communicable disease have shorter incubation period as per
the compared to the non-communicable disease .
Non-communicable disease such as- heart disease,
hypertension and cancer.
Communicable disease such as- Meascles , Mumps ,
Chickenpox.
NATURAL HISTORY OF THE DISEASE:-
Disease usually occurs in two phases :-
Pre pathogenic phase
Pathogenic phase
oPre Pathogenic Phase :- This period before occurring disease.
Agent, host, and environment factor this three are known as
epidemiological triad.

9. AGENT
HOST ENVIRONMENT
Agent factor:- The agent is a substance that may be living or non-living or
factor which is responsible for initiating the disease . The disease producing
agents are classified as biological ,Physical, chemical, and social agent.
Host factor :- The human being or animals who contact with agent , when the
resistance of the host low the agent succeed producing disease host factor such as
biological , chemical , physical.
Environment factor :- The environment factors play as important role in the
individual health. The environment factor are two- Internal and External.
Internal:- Tissue , Organ, Body system .
External:-Air, Water.

10. CLASSIFICATION OF ENVIRONMENT :-
1. Physical environment:- All physical factors such
as air, water, food, heat, cold.
2. Biological environment :- All living things
around man i.g:- microorganism, animal ,
plants
3. Psychosocial environment including lifestyle ,
attitudes.

11. SUMMARY:-
As the basic science of public health ,
epidemiology includes the study of the
frequency pattern , and causes of health –
related status or events in population , and the
application of that study of disease condition
and diagnosis the problem and giving the well-
being of community.