Epidemiology is the study of disease patterns in populations and the factors influencing health. It combines elements of biology, social sciences, and ecology with statistics to describe disease occurrence and investigate causes. Epidemiology provides opportunities to prevent and control diseases by identifying risk factors, evaluating treatments, and improving health services. It covers disease distribution, causation, and health-related events in populations and is considered the basic science of prevention and social medicine.

1. EPIDEMIOLOGY
INTRODUCTION :Epidemiology is the basic science of
prevention & social medicine. Epidemiology is concerned
with the improvement of health. It has evolved rapidly
during the past few decades. It is the science which
describe the disease pattern in the population. The diseases
occur due to multiplicative interactions between the
individual, societies & environment. The science of
epidemiology combines elements of biology, social
sciences & ecology complemented by statistics. On the
basis of all these, epidemiology is considered as a
multidisciplinary science. Epidemiology is also concerned
with the practice as it puts its knowledge to prevent
&control the disease.

2. Epidemiology has provided new opportunities
for prevention, treatment, planning & improving the
health services efficiency by identifying risk factors
of chronic disease, evaluating treatment modalities
&health services. Its ramification covers disease
distribution, causation, health & health related
events occurring in the population. It is considered
as the basic science of prevention as well as social
medicine.

3. • The current interest of medical sciences in
epidemiology has given rise to newer off-shoots
such as infectious disease epidemiology, chronic
disease epidemiology, clinical epidemiology,
serological epidemiology, cancer epidemiology,
malaria epidemiology, neuro epidemiology,
genetic epidemiology, occupational epidemiology,
psychological epidemiology, & so on. This trend is
bound to increase in view of the increasing
importance given to the pursuit of
epidemiological studies.
•

4. Epidemiology & Nursing
Nursing’s epidemiological roots can be traced to Florence Nightingale.
Nightingale regularly sought advice on issues related to hospital statistics
& disease classification from her close friend William Farr, who
established the field of medical statistics, General Register Office for
health & vital statistics, England.
Her comprehensive records on disease (morbidity) statistics, health
status of the soldiers in the Crimean war one of the first systematic
descriptive studies of the disease distribution & patterns in a population.
She had brilliantly used wedge- shaped graphs, circles, & squares that
were shaped & colored to explain preventable deaths of the hospitalized
Crimean soldiers, compared with hospitalized soldiers in England at the
time. This gave her the name “ First nursing researcher”.

5. DEFINITION :
Epidemiology is the term derived from the Greek words
epidemic dating back to the 3rd century. The word epidemic
have the meaning:
Epi: Upon
Demos: People
Logos : knowledge
It means epidemiology is epi (upon) + demos (people) +
logos (study) i.e. epidemiology is the study of what
happens to the people. In modern parlance, Epidemiology
is, “the study of disease in population”. Traditionally,
Epidemiology related to studies of human populations, &
epizootiology as the studies of animals (excluding human)
populations (Karstad, 1962). Outbreaks of disease in human
population were called “epidemics”, in animal population
were called ‘epizootics’, & in avian populations were called
‘epornitics’.

6. • In other words, epidemiology is the study of the
spread of diseases within & between populations.
Epidemiology is defined as the study of how often
diseases occur in different groups of people & why.
It is considered as the study of factors affecting the
health status of the populations & serves as rational
for interventions made in the interest of public
health. It is considered as a cornerstone
methodology of the public health research. It is also
regarded as evidence – based medicine for
identifying risk factors for disease & determining
optimal treatment approaches to clinical practice.

7. • According to Thrushfield, M (1995) Epidemiology
is the study of disease in populations & of factors
that determine its occurrence.
• According to U.S. National Institute of Health,
“Epidemiology is the study of the patterns,
causes, &control of diseases in groups of people.
• Epidemiology has been defined by John M Last in
1988 as: - “The study of the distribution &
determinants of health related states or events in
specified populations, & the application of this
study to the control of health problems”.The
various words used in this definition have the
meanings such as:

8. • Study: Epidemiology gives vision to make scientific
questions & that provides the foundation for further
construction of this discipline. Epidemiology also absorbs
methods from other scientific fields that includes but not
limited to biostatistics
• Distribution: The disease is not distributed uniformly in
human population but it occurs in patters in community.
The epidemiology studies this pattern of distribution in
population in relation to time (whether an increase or
decrease over the time span), place (more concentrated in
one area than other) & classes of persons affected (more in
man, women, age specific, particular occupation etc.). As
the disease pattern is described, it helps in formulation of
aetiological hypothesis & lead to take appropriate
measures to control or prevent the disease. Descriptive
epidemiology determines the distribution of disease
pattern in population.