Introduction to public health. used to ev h students pptx

MDG Health Needs Assessment
Unit one
Introduction to
Public Health
Principles and
concepts of Public Health

Discussion points
Definition;
Health,
Diseases and Public Health in General
 Determinants Of Health
 Disease Causation
 Prevention Strategies
 …….

Definition of major terms/concepts
 Health
• The concept of health is often difficult to define
and measure
• It is a broad concept and experience. Its boundary
extends beyond the "sick”
It depends on:
1) The perception of individuals
2) The threshold - e.g. pain
3) the ability to recognize symptoms and signs

 WHO …..definition
 Health:
is a state of complete physical, mental and social
well-being and not merely the absence of diseas
e
or infirmity
 Wellness: an active process by which an
individual progresses towards maximum
potential towards healthy condition, regardless
of current state of health

• Wellness is an active, lifelong process of becoming
aware of choices and making decisions toward a
more balanced and fulfilling life
• Let you discuss about;
• What elements/components are potentially
determine individual wellness (aspects of health)?

Components of Wellness
1. physical, e.g.:
• Ability to carry out daily tasks
• achieve fitness
• Maintain nutrition and proper body fat
• Avoid abusing drugs, alcohol, or using tobacco
products
• Generally to practice positive life-style habits
October 26, 2024 Azeb G 6

2. Social, e.g.:
• ability to interact successfully with people and
within the environment of which each person
is a part
• develop and maintain intimacy with significant
others
• develop respect and tolerance for those with
different opinions and beliefs

3. Emotional, e.g.:
• Ability to manage stress and express emotions
appropriately
• Ability to recognize, accept, and express feelings
• Ability to accept one’s limitations
4. Intellectual, e.g.:
• Ability to learn and use information effectively
for personal, family, and career development
• Striving for continued growth and learning to
deal with new challenges effectively

5. Spiritual, e.g.:
• Belief in some force (nature, science, religion, or a
"higher power") that serves to unite human beings
and provide meaning and purpose to life
• Includes a person’s morals, values, and ethics
6. Occupational
• ability to achieve a balance between work and
leisure time
• beliefs about education, employment and home
influence personal satisfaction and relationships
with others

 Disease: the condition of the human body in
which something has gone wrong and has
upset the normal functions of the body including
the mind
• The International Classification of Disease
(ICD) distinguishes between three terms:
 Impairment
 any loss or abnormality of mental, anatomical
or morphological, physiological structure of
function

 Disability - is any restriction or lack, resulting
from impairment, of the ability to perform an
activity in a manner or range considered normal
for a human being
 Absence of competent physical, intellectual, or
moral power, means, and the like
 Handicap - is a long-term disadvantage which
adversely affects an individual's capacity to
achieve the personal and economic
independence that is normal for one's peers

Aspects of health
 Physical health:
good body health, and is the result of regular ex
ercise
, proper diet and nutrition, and proper rest for
physical recovery
 Mental health: individual's emotional and
psychological well-being
 Social health: the ability to make and maintain
relationships with other people

 Emotional Health: refers to our sense of well-
being and our ability to cope with life events
• Concerned with the way we think and feel
• It refers to our ability to acknowledge and respect
our own emotions as well as those of others
 All these aspects:- emotional, physical, and social—
must function together to achieve overall health

Holistic Concept of Health
 Quality of life that has dimensions and is being
influenced by many factors
 Interdependent and inter- related each other
14

Health maintenance
• Achieving health and remaining healthy is an active
process
• Effective strategies for staying healthy and improving
one's health include the following elements:
Nutrition
• What people eat affects their health and
performance, such as foods or food components that
cause diseases or deteriorate health

Exercise
• Frequent and regular physical exercise is an
important component in the prevention of some of
the diseases
Hygiene and sanitation
• Hygiene is the practice of keeping the body clean to
prevent infection and illness, and the avoidance of
contact with infectious agents

Stress management
• Prolonged psychological stress may negatively
impact health, such as by weakening the immune
system
Health care
• Health care is the prevention, treatment, and ma
nagement of illness and the preservation of me
ntal and physical well being through the services
allied
health professions
17

• According to the WHO, health care embraces all
the goods and services designed to promote
health, including “preventive, curative and
palliative interventions, whether directed to
individuals or to populations”
18 18

Workplace wellness programs:
this can include things like promoting health through
• onsite fitness centers,
• health education,
• wellness newsletters,
• access to health coaching,
• tobacco cessation programs

Public Health Definition
• …the health status of a defined group of people and
the actions and conditions both private and public
(governmental) to promote, protect and preserve
their health.
the science and the art of preventing disease,
prolonging life & promoting physical health and
efficiency through organized community efforts for
sanitation of the environment, the control of
community infections

defined …
 …, the education of the individual in principles of personal
hygiene, the organization of medical and nursing services
for the early diagnosis and preventive treatment of disease
and
 the development of the social machinery which will ensure
to every individual in the community a standard of living
adequate for the maintenance of health.[Charles Edward A.
Winslow ]

The core functions of public health are
22
 Assessment : the diagnostic function (collection,
assembling, analysis)
 Researching to develop new insights and innovative
solutions;
 Monitoring the health status of the population;
 Policy development: formulating a strategic approach to
improving the community health
 Leading the development of sound health policy and
planning.

Core
23
 Assurance: making the services needed for the protection
of public health in the community are available and
accessible to everyone.
 Assuring the quality, accessibility, & accountability of
medical care;
 Reaching out to link high risk and hard to reach people
in medical services;
 Preventing epidemics;
 Protecting the environment, work place, food and
water;
 Promoting healthy behavior;
 Mobilizing community action;
 Responding to disasters;

Mission of public health
24
….“fulfilling society’s interest in assuring conditions
in which people can be healthy”.
Philosophies
The factor most significant in determining the
health of a community is its economic status
Effective public health programs save money on
medical costs in addition to saving lives.

Determinants or factors
of public health

Determinant/factors
• Physical Determinants:
– Geography
– Environment
– Industrial development
• Socio cultural Determinants:
– Beliefs, traditions & norms;
– Economy
– Politics;
– Religion
 Community Organization:
 Community size
 Arrangement and
distribution of
resources (“relations of
production”)
 Behavioral Determinants
 Individual behavior and
life style

Environment: (Source of living)
Human ecology
 Physical Environment:
– condition of roads for driving (Vs Accidents, pollution)
 Climate:
– harvest, insect breading, etc (Vs famine, malnutrition)
– temperature, humidity, rainfall, radiation, altitude, etc
 Terrain: hilly, forest, desert, marshy, island
 Housing: ventilation, housing light, hazards etc
 Sanitation: drinking water, waste management, hygiene, etc
 Work place: noise, chemicals, etc

Social & Political environment:
– Life style, living status, poverty, education, gender status,
employment, food availability, etc
– governance, law, corruption, instability, etc
Geography: Kola, WeinaDega, Dega Vs diseases

Other ways of looking in the
classification of factors
Four types
1. Predisposing Factor [as f(Host)]
Factors that may create a state of susceptibility
Ex: Age, (childhood, elderly); Sex, (women for depression)
2. Enabling Factors [as a f(env’t)]
Events or conditions that favor development of disease
or an outcome of interest.
Factors such as low income, poor nutrition, bad housing, lack of
access to health Institutions
Factors that assist in recovery from disease like maintenance of
good health could also be grouped here.

Other…
3. Precipitating Factors [f(exposure]
– Events or conditions that favor exposure to a specific
disease agent.
– They may be associated with the onset of the disease
Ex: Wound, physical trauma, Tetanus, STIs, HIV/AIDS
4. Reinforcing Factors [f(transmission]
– Factors that aggravate an established disease.
Ex: Repeated contact to infectious agent
Common cold within a household

Multi-causal Theory
(Web of Disease Causation)
• It has even enlarged and elaborated on the host-
agent-environment triad wherein each of these
factors affects the other
• The four models are:
1. Epidemiologic triangle & triad (balance beam) model
2.Sufficient and component causes model
3.Webs model
4.Wheel model of infectious diseases

Models of causation
I. Models of Explanation
– It is a model that could assess reasons for an effect
happening
– It is more of social science phenomena
II. Ecological models
– It is a model applicable to infectious and non-
infectious causes of disease
III. Bradford-Hill criteria
– Criteria of causation
33

I. Models of Explanation
a. Idiographic model aims at a complete understanding of a
particular phenomenon, using all relevant causal factors
– Enumerates detailed/unique factors that lie behind some
action or social fact
– Lists all possible factors as reasons for the occurrence of
the outcome
b. Nomothetic model aims at a general understanding of a
class of phenomenon, using the smallest number of most relevant
causal factors.
The nomothetic model is probabilistic in its approach to causation.
It is the model typically used in social scientific research.
– Isolates the few key characteristics uniting similar cases
– Isolates the few core reasons of an outcome
34

a. Idiographic explanation
• Example- “Taking this introduction to public
health course”
• There are a number of reasons for why you are taking this
course. … if you start listing…. You can list thirty or forty …
– Reasons
…. may be high-minded, ….. to help you satisfy
your interest in exploring pedagogical methods.
…… may be more routine reason: the course is
required, it fit into your schedule.
• If you list as many as you can it would help people to fully
understood why you are doing it.
35

b. Nomothetic explanation
• But in a nomothetic explanation
– it offers a partial explanation for the behaviors that
represent many people.
– Such explanations are not singling out certain reasons
rather they provide a more generally applicable
explanation.
– Therefore, it is probabilistic, not certain or complete.
36

II. Three ecological models
1. The Epidemiologic Triangle (Triad)
– consist of three components
1) host, 2) environment and 3) agent.
– A change in any of the components will alter an existing
equilibrium to increase or decrease the frequency of the
disease.
37
ENVIR
AG
EN
T
H
O
ST

Epidemiologic triangle & triad (balance beam) model
Traditional model of infectious disease causation
Agent
Host
Environment
Epidemiologic triangle
Host
Agent
Environment
Balance beam
38

2. The Web of Causation
• The essence is that
– Effects (diseases) never depend on single isolated
causes,
RATHER it develops as a result of chains of inter-
related causes.
• The large number of inter-related causes, are
considered as a “web”
Eg Pulmonary Tuberculosis-
• Patients lower immunity + M. Tbc
• Malnutrition, HIV/AIDS, Age, Cancer
39

web model
• It is in response to the
idea of non-infectious
diseases having no
unique agent
• There is no single
cause
• Causes of disease are
interacting
40

Web of Causation
Disease
behavior
U
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s
genes
phenotype
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microbes
environment

Web of Causation - CVD
42
Disease
smoking
U
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f
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gender
genetic susceptibility
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lipids
physical activity
b
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3. The Wheel / Pie Modelcomponent causes model
• This has come for multi-factorial nature of causation in
many diseases.
Sufficient Cause:
• The whole components of a pie make the sufficient
cause for a disease.
– A disease may have only one factor as a sufficient
cause to develop a disease. Eg. Rabies
– A disease may have more than one sufficient cause,
each sufficient cause is composed of several
component causes.
43
C
D
A
B

Cont..
• In this traditional model, each component cause is seen as
necessary and sufficient cause in itself to produce the
effect.
• Necessary cause: A causal factor whose presence is
required for the occurrence of the disease.
– A factor (contributing) that is necessary (or with out which) the
disease doesn’t exist or occur
• Sufficient cause. A causal factor or collection of factors
whose presence is always followed by the occurrence of
the disease.
Multiple-causality of diseases

Wheel cont..
Genetic
core
(Humans)
Social
environment
Physical
environment
Biologic
environment
Host
The interaction of humans with infectious agents and their environment, a
person’s state of health represents a dynamic equilibrium – a balance of
Agent
Agent
Agent
Agent

III. Bradford-Hill criteria
In judging the different aspects of causation,
 The correct temporal relationship is essential,
 Once the above fulfilled, weight should be
given to:
– Plausibility, [logically cause, clinical implication]
– Consistency, [other researches should support]
– dose-response relationship and
– Strength of the association
– Specificity of the relation
46

Establishing Causality
 To establish whether two variables are causally related, we must
establish:
 Time order (temporal relationship): The cause must
have occurred before the effect
 Statistical association: Changes in the value of the
independent variable must be accompanied by changes
in the value of the dependent variable
 Rationale: There must be a logical and compelling
explanation for why these two variables are related
 Non-spuriousness: It must be established that the
47

Models based on level
• Levels of prevention is related with natural history
of a disease
• It involves the interruption or slowing of disease
progression through appropriate interventions.
• It is through identifying modifiable causes of the
disease and its risk factors
49

• Natural history time lines for infection
and disease
Usual time
of diagnosis
Pathologic Onset of
Exposure Changes Symptoms
Stage of Stage of Stage of Stage of Recovery,
Susceptibility Subclinical Clinical Disability or Death
Disease Disease
50
Time
Natural History of Diseases
• Refers to the progress of a disease process, in the
absence of intervention.

Cont….
• There are several stages during the course of a
disease at which we can intervene in order to control
the disease.
• Three levels, (Primary, Secondary and Tertiary)
I. Primary prevention
Objectives –
promote health,
prevent exposure, and
prevent disease.
51

Cont…
A. Health promotion (Primordial):
• It is general non-specific interventions that enhance
health and the body’s ability to resist disease
• It is more of communal than individual effect
(governments, NGOs, international organizations effort)
• Example- improvement of socioeconomic status through
the provision of adequate….
– paid jobs,
– education,
– affordable and adequate housing and clothing, etc.
– Millennium Development Goal
52

Cont…
B. Prevention of exposure:
• Relatively specific compared to primordial
prevention
– Example for communicable disease
 provision of safe & adequate water, proper excreta
disposal,
 vector control;
 Provision of a safe environment at home
– Example of non-communicable
 Slow driving for prevention of car accident injury,
53

Cont…
C. Prevention of disease:
– Example -immunization.
– Some intervention can act at more that one level
• Example- Breastfeeding is an example of an
intervention which acts at all three levels of
primary prevention.
54

Cont…
II. Secondary prevention
–Interventions that act after the biological onset of
disease, but before permanent damage sets in.
–Objective - to stop or slow the progression of
disease so as to prevent or limit permanent
damage.
–Strategy - early detection and treatment of
disease.
55

Cont…
III. Tertiary prevention
• Intervention that acts after permanent damage
has set in,
• Objective - to limit the impact of that damage.
• The impact can be physical, psychological, social
(social stigma or avoidance by others), and
financial.
• Strategy - is rehabilitative.
56

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