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EPDIMEOLOGY.pptx
1. Introduction
Epidemiology ", is derived from Greek. epi,
meaning "upon, among", demos, meaning
"people", and logos, meaning "study,
2. Definition
• Epidemiology is defined as the study of
distribution and determinants of health
related states in specific populations, and use
of this study to control the health related
problems.
3. Aims of epidemiology
• According to the international epidemiological
association ,3 main
• a)to describe the distribution and magnitude of health
and disease problems in human population
• b)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 ,control and treatment of disease and to
the setting up of priorities among those services
4. Cont ….
• The ultimate aim of epidemiology is to lead to
effective action
• a) to eliminate or reduce the health problem
or its consequences and,
• b)to promote the health and well-being of
society as a whole
5. Objectives
• General objectives
~Explaining the casual mechanism of disease
and process of deviation in health
~Explaining the reason for local disease
occurrence
~Effective planning and administration of
health care services
6. Specific objective
• 1)Understanding causation of disease with
specific purpose
• 2)Testing validity of rationale of
control/intervention programs
• 3)Classify disease/disability based on
distribution casual factors and natural history
of disease
7. • 4)Explaining local disease pattern
• 5)administrative guidance
- in assessing need, utilization and
effectiveness
- in in monitoring and evaluation of control
programs
12. Epidemiological approach
• The Epidemiological approach to problems of
health an disease is based on two major
foundation
A) Asking question .
1)Related to health events
2)Related to health action
B) Making comparison
13. Basic measurement in epidemiology
• Epidemiology focuses ,among there things, on
measurement of mortality and morbidity in
human population
A)Measurement of mortality
B)Measurement of morbidity
C)Measurement of Disability
D) Measurement of Fatality
14. E)Measurement of presence ,absence or
distribution of characteristic of disease
F) Measurement of medical need, health care
facilities, utilization of health service and other
health related events.
G) Measurement of the presence ,absence of the
environmental and other factors suspected of
causing disease
17. • Rate-measures the occurrence of some
particular event(development of disease or
the occurrence of death)in a population
during a given time period
Death rate =
Number of death in one year × 1000
Mid–year population
18. • Various categories of rate
a)Crude rate-actual observe rate such as birth
and death rate
b)Specific rate- actual observe rate due to
specific causes, or occurring in specific
time, and group Eg tuberculosis, accident
c)Standardized rate-direct or indirect method or
adjustment like age,sex
19. Ratio
• Another measure of disease frequency is a ratio. it
expresses a relation in size between two random
quantity eg.sex ratio, child women ratio
20. Proportion
A proportion is a ratio which indicates the relation in
magnitude of a part to a whole and always expressed
as percentage
E.g.
No. of children with scabies at certain time X 100
The total number of children in the village
at the same time
22. • Death certificate used in India
a) To improve the quality of maternal mortality and
infant mortality data
b) To provide alternative method of data collection
during pregnancy and infancy
23. Uses of mortality data
A)Explaining trends
B)Differential in overall motility
C)Priorities for health action
28. HUMAN RESERVIOR
• Cases –a person in the population ,having particular
disease, under investigation
-Epidemiological terminology
a. primary case
b. index case
c. secondary case
29. classification
Carrier may be classified as
a. Type
1 . Incubatory carriers- They shed the infectious
agent during the incubation period of the disease.
They can infect others even before the onset of
illness.
30. • 2 . Convalescent carriers-They shed the
infectious agent during the period of recovery.
• 3. Healthy carriers:
They are apparently healthy individuals with
subclinical infection. But they can transmit the
disease
31. b.Duration-
1.Temporary carriers -They shed the infectious
agent for short periods.
2. Chronic carriers: They shed the infections
agent for index- finite periods.
32. C. Portal Of Exit
-Urinary Tract
-Intestinal
-Respiratory
-Other
33. Animal reservoir
• Animal reservoir –
Sometimes the source of infection may be animals
and birds. They transmit a variety of diseases.
Diseases transmitted by animals and birds are
called as Zoonotic diseases e.g. rabies, yellow fever.
34. Reservoir in non – living things
• Reservoir in non – living things
Soil and inanimate objects can act as reservoir of
infections. For example, soil acts as a reservoir for
tetanus and anthrax.
35. MODES OF TRANSMISSION
The communicable disease may be transmitted from
the source or reservoir, the infectious agent can be
transmitted to the host either directly or indirectly.
a. Direct transmission
b.Indirect transmission
36. Direct transmission: It can occur by:
1. Direct contact:
This can occur from skin to skin, skin to mucosa or
mucosa to skin of the same or different person.
2. Droplet infection:
The infectious agent is sprayed as droplets of saliva
or other secretions. This can occur while coughing,
sneezing or talking.
37. 3. Contact with soil:
Infections like tetanus are contacted from soil.
4. Inoculation to skin or mucosa:
AIDS is transmitted through contaminated needles and
syringes
5. Trans placental (or vertical) transmission: Diseases
like syphilis and AIDS are transmitted through placenta.
38. Indirect transmission:
Indirect transmission: It occurs through the five
traditional F’s
1. Fluid and Food – vehicles borne
2. Flies – vector borne
3. Fomites – Fomite borne
4. Fingers and hands – Finger borne
5.Air borne-Droplet, Dust
39. SUSCEPTIBLE HOST
• In the host, four stages are involved in an infection.
1. Entry
2. Colonization
3. Exit
4. Survival Outside
40. 1. Entry: The infectious agent enters the host through
any possible route e.g. respiratory tract, alimentary
tract, skin etc.
2. Colonization: After entry into the host, the infectious
agent chooses a suitable site in the body like lungs,
brain or liver. It grows and multiplies at these sites.
41. 3. Exit: After multiplication it comes out of the host
through any possible route like feces, urine or saliva.
4 Survival outside: After exit from the host, the
infectious agent survives in the external environment
till it finds a new host.
42. Disease prevention and control
1)Controlling the reservoir
a)Early diagnosis
b)Notification
c)Epidemiological investigation
d)Isolation
e)Treatment
f)Quarantine
43. 2)Interruption of transmission
3)The susceptible host
a)active immunization
b)passive immunization
c)combined passive and active immunization
d)chemoprophylaxis
e)non- specific measures
45. Uses of epidemiology
• In historical study of the health of the community
and of the rise and fall of diseases in the population;
useful ‘projections' into the future may also be
possible.
• For community diagnosis of the presence, nature and
distribution of health and disease among the
population
46. • To study the workings of health services. .
• To estimate, from the common experience, the
individual's chances and risks of disease.
• planning and evaluation
47. • In identifying syndromes from the distribution of
clinical phenomena among sections of the
population.
• In the search for causes and risk of health and
disease.
