for health Introduction to Epidemiologist

Introduction to epidemiology
Mr. Faisal Muhammad
Lecturer & IMPH Coordinator,
Department of Public Health, DIU

Objectives
 At the end of the session the students will be able to :
 What is ‘’Epidemiology’’?
 Summarize the historical context of epidemiology
 Scope of epidemiology and common epidemiological terms
 To know about modern epidemiology and evolution of
epidemiology
 What is epidemiology of health?

The word ‘’epidemiology’’
 The word Epidemiology has come from the three Greek words: Epi
, Demos and Logos.
 Epi means ‘ on’ or ‘upon’, Demos means people or population and
logos means words ‘the study of’, which is a very old dating back to
the 3rd
century B.C. Thus epidemiology means study of what
happens to the people.
 Epidemiology is the study of how often diseases occur in different
groups of people and why. Epidemiological information is used to
plan and evaluate strategies to prevent illness and as a guide to the
management of patients in whom disease has already developed.

Epidemiology: Definition
 Epidemiology is the study of distribution and
determinants of health related states and events in a
specified population and application of this studies
to control of health problems.
--Principles of Epidemiology, CDC

Study
 As you study this definition , refers to the description
of these terms below:
 Study- Epidemiology is a scientific discipline,
sometimes called “the basic science of public
health.” It has, at its foundation, sound methods of
scientific inquiry.

Distribution
 Distribution- Epidemiology is concerned with the 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. The rate (number of events divided by size of the
population) is critical to epidemiologists because it allows valid comparisons across different
populations.
o Pattern refers to the occurrence of health-related events by time, place, and personal
characteristics.
o • Time characteristics include annual occurrence, seasonal occurrence, and daily or even
hourly occurrence during an epidemic.
o • Place characteristics include geographic variation, urban-rural differences, and location of
worksites or schools.
o Personal characteristics include demographic factors such as age, race, sex, marital status, and
socioeconomic status, as well as behaviors and environmental exposures

Determinants
 Determinants: Epidemiology is also used to search for
causes and other factors that influence the occurrence of
health-related events. Analytic epidemiology attempts to
provide the Why and How of such events by comparing groups
with different rates of disease occurrence and with differences
in demographic characteristics, genetic or immunologic make-
up, behaviors, environmental exposures, and other so-called
potential risk factors.
 Under ideal circumstances epidemiologic findings
provide sufficient evidence to direct swift and effective
public health control and prevention measures.

States and events
 States- The condition of health , diseases, disability,
discomfort, dissatisfaction, health needs, health
demands, health activities, health care utilizations,
lifestyles , etc.
Events – The vital events like birth , death, marriage,
divorce , migration , etc, accidents like road traffic
accidents, warts, flood, poisoning , nuclear explosion
etc.

Specified population
Specified population – Population in a defined
geographical area with a specific characteristics.

Application
 Epidemiology is more than “the study of.” As a discipline within
public health, epidemiology provides data for directing public health
action. Similarly, an epidemiologist uses the scientific methods of
descriptive and analytic epidemiology in “diagnosing” the health of a
community, but also must call upon experience and creativity when
planning how to control and prevent disease in the community.
 This can be done by informing health policy makers to take necessary
action on some problem revealed by the study by providing
intervention.
 The researcher can also experiment on a group of people by certain
intervention measures to bring about desired change in those people.

Control
Control of health problems :
If distribution and cause of any health related matter
is known , we can control the problems created from
that particular health related state and event.

Hippocrates (460-377 B.C)
Idea that disease might be
associated with physical
environment ‘’ On air, water
and places ‘’
History of Epidemiology

Thomas Sydenham (1624-1689)
Recognized as a founder of
clinical medicine and
epidemiology.
Emphasized detailed
observations of patients &
accurate recordkeeping.

James Lind (1700’s)
 Designed first experiments to
use a concurrently treated
control group

Edward Jenner (1749-1823)
 Pioneered clinical trials for vaccination to
control spread of smallpox
 Jenner's work influenced many others,
including Louis Pasteur who developed
vaccines against rabies and other
infectious diseases

Ignas Semmelweis (1840’s)
 Pioneered hand washing to
help prevent the spread of
septic infections in mothers
following birth

John Snow (1813-1858)
Father of epidemiology
Careful mapping of cholera
cases in East London during
cholera epidemic of 1854
Traced source to a single well on
Broad Street that had been
contaminated by sewage

Typhoid Mary & George Soper
Mary Mallon, a cook responsible for most
famous outbreaks of carrier-borne disease in
medical history
Recognized as carrier during 1904 N.Y. typhoid
fever epidemic
When source of disease was traced, Mary had
disappeared only to resurface in 1907 when more
cases occurred
Again Mary fled, but authorities led by George
Soper, caught her and had her quarantined on an
island

, In 1910 the health department released her on
condition that she never accept employment
involving the handling of food
Four years later, Soper began looking for Mary
again when two new epidemics broke out; Mary
had worked as a cook at both places
She was found and returned to North Brother
Island, where she remained the rest of her life
until a paralytic stroke in 1932 led to her slow
death.

Future Challenges
 Instant global transmission of pathogens
 Population overcrowding
 Ease of travel
 Importation of foods

Concept of epidemiology
 Over two thousand years ago Hippocrates gave us the earliest impression about
epidemiology ‘s content or approach in his treatise on ‘’ air, water and places’’.
 Thereafter evolution of epidemiological concepts have taken place through work of different
scientists over different periods.
 These works generated ideas which lead to development of present day epidemiological
concepts and methods have developed from four central ideas. These are:
 1. Observation: that human diseases is related to man’s environment – as postulated by
Hippocrates.
 2. Counting: of natural phenomenon may be educative as demonstrated by John Graunt
1962 in his analysis of Bills Of mortality.
 3. Natural experiments : can be utilized to investigate etiology and mechanism of disease
process – as illustrated by John Snow (1854) in his investigation work on Cholera in London.
 4. Experiments on man : Under certain conditions , can also be used for this purpose –
as was the case in experiment by Fletcher (1905) on effect of cured rice on prevalence of
Beriberi in kuala lampur prison.

Epidemiology :concerned
 Basic science concerned with the pattern of diseases frequency in
human population.
 Not only the disease, disability and health but also with more positive
health states and with the men to improve health.
 Facts of life occurring in human population.
 The study of health services used by the population and to measure
their impact.
 Epidemiology is often concerned with the well being of society as a
whole than with the well being of individuals

Purpose of epidemiology
 To provide a basis for developing disease control and
prevention measures for groups at risk . This
translate into developing measures to prevent or
control disease.

Aims of epidemiology
 To describe the distribution and magnitude of health
and disease problems in human population.
 To identify etiological factors (risk factors) in the
pathogenesis of diseases.
 And provide data essential to planning ,
implementation and evolution of services for the
prevention, control and treatment of disease and to
the setting up of priorities among those services.

Epidemiology of health
 Epidemiology of health is the study of distribution and determinants of
health itself or in other words , to study the factors related with two
factors:
 a) in the absence of disease condition , for example small pox and the
another.
 b) in the absence of a disease in a community in spite of presence and
exposure to specific risk factor responsible for the causation of the said
disease.
 Therefore if all the diseases were eliminated , the epidemiology continue
to study about the determinants of health to promote the health status of
population. For example , small –pox has been eradicated from the
world , but surveillance of small pox is still continuing.

Modern epidemiology
 Modern epidemiology deals with , in addition to chronic diseases,
the other health related states that is not a medical condition but can
give rise to health consequences.
 The concept has started with the search for non –communicable
diseases and its horizon towards genetic epidemiology, pharmaco-
epidemiology, immuno-epidemiology, social epidemiology etc.
 Modern epidemiology has entered the most exciting phase of its
evolution. By identifying risk factors of the chronic diseases,
evaluating treatment modalities and health services, it has provided
new opportunities for prevention, treatment , planning and
improving effectiveness and efficiency of health services.

Use of epidemiology
 1. To determine which in the three possible sets of disease factors, host , agent and
environment , are important in the occurrence of specific disease or class of disease,
the extent to which those factors are important and the manner in which they
interact.
 2. To study the occurrence of disease in a population for purposes of community
diagnosis and prognosis.
 3. To describe the epidemiology of disease or class of disease.
 4. To measure risk.
 5. To study the occurrence of disease or death with time as variable. Such a study is
referred to as a historical study.
 6. To aid the search for cause of a disease.
 7.In disease prevention and control.
 8.To aid the identification of clinical syndrome.
 9. To aid the detection of pre symptomatic and latent disease.
 10. In administrative medicine and operational research

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