Epidemiology is defined as the study of the distribution and determinants of health and disease in populations. The aims of epidemiology are to describe disease problems, identify causal factors, and provide data to plan and evaluate prevention and control efforts. The epidemiological triad examines the interaction between host, agent, and environment in disease causation. It considers how personal, biological, and environmental characteristics bring a host in contact with a disease-causing agent. Epidemics occur when there is an imbalance between these factors, such as a new or changing agent, changes in population susceptibility, or environmental conditions that influence disease transmission.

1. EPIDEMIOLOGY
Dr khyati boriya

2. • DEFINATION :
• AIMS & OBJECTIVES
• EPIDEMIOLOGICAL TRIAD

3. What is Epidemiology?
• Last’s dictionary gives a
detailed definition:
• The study of the distribution and
health-related determinants.
• states or events in specified
populations.
• study to control of health
problems.

4. • What is Epidemiology?
• Epidemiology is the study of the
determinants, distribution, and
• frequency of disease (who gets
the disease and why)

5. • epidemiologists study healthy
people
• to determine the difference
between those who get exposed
and non-exposed people
• epidemiologists study exposed
people

6. • AIMS OF EPIDEMIOLOGY
a) To describe the distribution and
magnitude of health and
diseases problems in human
population.
b) To identify etiological factors in
the pathogenesis diseases.
c) To provide the data essential to
the planning, implementation
and evaluation of services for
the prevention, control and
treatment of diseases.

7. OBJECTIVES:
• able to understand the concepts of
health dynamics, modes of disease
transmission and levels of control
and prevention.
• able to compute validity familiar
with the brief history of
epidemiology, historical
epidemiological investigations
and interventions.

8. • to understand design and
application of various
Epidemiologic methods.
• able to understand and briefly
discuss design and interpret public
health surveillance.
• able to understand methods of
investigations of
outbreaks/epidemics.
• able to learn selected applications
of epidemiology in health
management such as situational
analysis, strategic planning,
quality assessment and evaluation
of health services.

9. The Epidemiologic
Triangle:
• three characteristics
• that are examined to study the
cause(s) for disease
• in analytic epidemiology

10. Basic triad of analytical
epidemiology
HOST
ENVIRONMENTAGENT

11. HOST
• personal traits
• behaviours
• genetic predisposition
• immunologic factors

12. Agents
• Biological (micro-organisms)
• Physical (temperature, radiation,
trauma, others)
• Chemical (acids, alkalis, poisons,
tobacco, others)
• Environmental (nutrients in diet,
allergens, others)

13. Environment
• Living conditions (housing, crowding, water
supply, refuse, sewage, etc)
• Atmosphere / climate
• Modes of communication: phenomena in the
environment that bring host and agent
together, such as: vector, vehicle, reservoir,
etc)

14. Epidemics occur when ..
host, agent and environmental factors
are not in balance due to new agent,
due to change in existing agent
(infectivity,
pathogenicity, virulence) due to change in
number of susceptible in the population
due to environmental
changes that affect transmission of the
agent of growth of the agent.