This document defines epidemiology and discusses key related concepts. It begins by defining epidemiology as "the study of the distribution and determinants of health-related states or events in specified populations." It then discusses key epidemiological terms like distribution, determinants, frequency, pattern, and the aims of epidemiology. The history of epidemiology is also summarized, highlighting the contributions of John Snow in identifying the water source of a cholera outbreak and Hippocrates' focus on environmental influences. Uses of epidemiology are listed as studying disease trends, planning health services, and searching for disease causes.

1. PRESENTED BY:
Jagan Kumar Ojha
MSc. Tutor
Dept. of Community Health Nursing
SNC

2. Epidemiology is derived from Greek word
“Epidemic”
EPI – On /upon
DEMOS – people
LOGOS – study of
Epidemiology means the study of disease in human
population.

3. DEFINITION
“The study of the distribution and determinants
of health-related states or events in specified
populations, and the application of this study for
the prevention and control of health problems” .
As defined by John M. Last (1988)

4. Definition….
Distribution ……
Frequency refers not only to the no. of health events such as
the no. of cases of meningitis or diabetes in a population but
also to the relationship of that number to the size of the
population. The resulting rate allows epidemiologists to
compare disease occurrence across different populations.
Pattern refers to the occurrence of health-related events by
time, place, and person.

5. Definition….
Determinants
 Determinants, which are the causes and other factors that
influence the occurrence of disease and other health-related
events.
 Illness does not occur randomly in a population, but happens only
when the right accumulation of risk factors or determinants exists
in an individual.

6. Other Definitions…
 The epidemiology is that branch of medical science
which deals with epidemics (Parkin, 1873)
 Epidemiology is the study of any disease, as a mass
phenomenon (Greenwood, 1934)
 It is the study of the disease frequency, distribution and
determinants among man (Mac Mohan- 1960)

7. AIMS
 To describe and measure the magnitude of health and
disease problems in human populations.
 To identify etiological factors in the pathogenesis of
disease.
 To provide the data essential to the planning,
implementation and evaluation of services for the
prevention and control of disease and to the setting up of
priorities among those services.

8. Objectives
 To identify the etiology or cause of disease
 To determine the extent of disease
 To study the progression of disease
 To evaluate preventive and therapeutic measures for
a disease or condition
 To develop public health policy

9. HISTORY OF EPIDEMIOLOGY

10.  JOHN SNOW - father of epidemiology
Snow conducted studies in 1854 when an epidemic of cholera erupted in
the Golden Square of London. He began his investigation by
determining where in this area persons with cholera lived and worked.
He marked each residence on a map of the area, as shown in Figure.
Snow believed that water was a source of infection for cholera, he
marked the location of water pumps on his spot map, then looked for a
relationship between the distribution of households with cases of cholera
and the location of pumps. He noticed that more case households
clustered around Pump A

11.  JOHN SNOW
However, that no cases of cholera had occurred in a two-block
area just to the east of the broad street pump. Upon
investigating, Snow found a brewery located there with a deep
well on the premises. Brewery workers got their water from
this well, and also received a daily portion of liquor. Access to
these uncontaminated rations could explain why none of the
brewery’s employees contracted cholera.

14. HIPPOCRATES
“ENVIRONMENTAL INFLUENCES”
On essay entitled “On Airs, Waters, and Places,” Hippocrates suggested that
environmental and host factors such as behaviors might influence the development
of disease.

15. FLORENCE NIGHTINGALE

19. Hence it refers to the progression of a disease process in an
individual over time, in the absence of treatment.
For example, untreated infection with HIV causes a spectrum
of clinical problems beginning at the time of seroconversion
(primary HIV) and terminating with AIDS and usually death.
Natural History of Disease

23. The uses of epidemiology are:
 To study the health history of population and their
disease trends.
 To arrive at community Diagnosis.
 To plan and evaluate health services.
 To estimate individuals risk and chance.
 To define and redefine syndromes.
 To complete the natural history of disease.
 To search for causes of health and disease by employing
epidemiological methods.
USES OF EPIDEMIOLOGY :

24. TERMINOLOGIES USED
IN
EPIDEMIOLOGY

25. INFECTION:
The entry and development or
multiplication of an infectious agent in the
body of man or animal.

26. EPIDEMIC
An epidemic is the rapid spread of infectious
disease to a large number of people in a given
population within a short period of time.

27. ENDEMIC
 The constant presence of a disease or
within ainfectious
geographical
agent
area or population
given
group,
without importation from outside. Eg.
Common cold.

28. PANDEMIC
 An
which
from
epidemic
spreads
country to
country or over the
whole world. Eg.
AIDS

29. SPORADIC
 Diseases that are seen only occasionally, and
usually without geographic concentration, are
called sporadic diseases.
 Examples… Tetanus, rabies, and plague.

30. ZOONOSIS
 Diseases or infections which
are transmitted from vertebrate
animal to human
 E.g. Rabies, plague

31. RESERVOIR
 The habitat ( place
for living) where an
infectious
living, grows
agent
and
multiplies.

32. Disease carrier could refer to: Asymptomatic carrier,
a person or organism infected with an infectious
disease agent, but displays no symptoms.
CARRIER

33. ISOLATION
 A separation
person
infectious
of a
with
disease
contact
human
with
beings
from
other
for the period of
communicability.

34. INCUBATION PERIOD
 This is the time interval
between the entry of the
disease agent into the body
and the appearance of first
sign and symptom of the
disease.

35. PATHOGENICITY
cause Ability to
the disease.

36. CONTAGIOUS
that is
through
A disease
transmitted
direct contact.
Eg. STD, flu..etc

37. VIRULENCE
 Measure the severity
of disease.

38. FOMITES
 Inanimate articles
than food or
contaminated
other
water
by the infectious
discharges.
e.g. Clothes, utensil,
furniture etc.

39. VECTOR
 Usually an arthropod eg.
Mosquito which transfers
an infectious agent from an
infected person to a healthy
person.
Ticks, mites, lice etc.

40. THANK YOU