Col Naseer Alam Tariq (Retd)
Webster defines disease
– A state in which body health is impaired,
a departure from a state of health, an
alteration of the human body
interrupting the performance of vital
– Oxford defines disease
A condition of the body or some part or
organ of the body in which its functions
are disrupted or deranged
• Ecological point of view disease is defined
A maladjustment of the human
organism to the environment
• The simplest definition of disease is
– Disease is just the opposite of health
– Any deviation from normal functioning
or state of complete physical or mental
well being
• WHO has defined health but not
• Disease literally means
“Without ease” (Uneasiness)
• Disease is opposite of ease
Concept of Causation of disease
• Various concepts of disease causation
– Supernatural theory of disease
– The theory of humors
– The concept of contagion
– Miasmatic theory of disease
– The theory of spontaneous
– Germ theory of disease
It is the way in which a disease evolves
over time from the earliest stage of its
pre-pathogenesis phase to its termination
as recovery, disability or death, in the
absence of treatment or prevention
• Period preliminary to the onset of
disease in man
• The diseases agent has not yet
entered the man.
• The factors which favour its
interaction with the human host are
already existing in the environment.
• The pathogenesis phase begins with
the entry of the disease agent in the
susceptible human host.
Natural History of Disease
Disease results from a complex
interaction between
man, agent and the environment
• The disease agent is
A substance , living or non living, or a
force, tangible or intangible, the
excessive presence or relative lack of
which may initiate or perpetuate a
disease process.
• Disease may have a single or a
number of independent agents or a
• Biological agents- living agent of disease
Bacteria, Viruses, protozoa, fungi,
• Nutrient agents- Protein, carbohydrate,
vitamins, minerals and water
Any excess or deficiency of the nutrient
elements may result in nutritional
disorders, anemia, goiter, obesity
• Physical agents –Exposure to excessive
heat, cold, humidity, pressure, radiation,
• Chemical agents- metal fumes, dust,
gases, insecticides
• Mechanical agents – exposure to
chronic friction and other mechanical
forces may result in crushing,
tearing, sprains, dislocations
• Social agents – poverty, smoking,
abuse of drugs, unhealthy life style,
social isolation
• Human host is referred as soil and the
disease agent as seed
• Host factors play a major role in
determining the outcome of an
individual's exposure to infection
• Host factors
– Demographic - age, sex, race
– Biological – genetic factors
– Social and economic factors
– Lifestyle factors
Environmental factors
• All that which is external to the individual
human host, living or nonliving and with
which he is in constant interaction
This include all surrounding such as
air, water, food, housing etc
Physical environment
Biological environment
Psychological environment
Spectrum of Disease
Spectrum of health
• Health and disease lie along a continuum,
and there is no single cut off point
The lowest point on the health-disease
spectrum is death and the highest point
positive health
Positive health
Better health
Freedom from sickness
Unrecognized sickness
Mild sickness
Severe sickness
Spectrum of Disease
• Variation in the manifestations of disease
• Disease spectrum are sub clinical
infections (unidentified) to fatal illnesses
• Illnesses ranging in severity from mild to
Iceberg of Disease
Iceberg of Disease
Iceberg of Disease
• Floating tip of the iceberg represents
what the physician sees in the
community-clinical cases
• The vast submerged portion of the
iceberg represents the hidden mass of
disease- latent, inapparent,
presymptomatic and undiagnosed cases
and carriers in the community
• Water line represents the demarcation
between apparent and inapparent disease
• The goals are
To promote health
To preserve health
To restore health when it is impaired
To minimize suffering and distress
Levels of Prevention
• Primordial Prevention
• Primary Prevention
• Secondary Protection
• Tertiary Prevention
Primordial Prevention
• Prevention of the emergence or
development of risk factors in a
population in which they have not yet
– Obesity origin in childhood
Life styles- eating patterns, physical
Main intervention in primordial
prevention is through individual and
mass education
• Directed towards discouraging children
from adopting harmful life styles.
• example – smoking leading to CPD
should be discouraged, Overeating
Primary Prevention
• Action taken prior to the onset of
• Removes the possibility the disease
will ever occur
• Intervention in the prepathogenesis
phase of a disease or health problem
– Health Promotion
– Specific Protection
Health Promotion
Measures to promote optimal level of
– Provision of adequate nutrition
– Health counseling to parents and
– Provision of adequate housing
– Health education, counseling
– Periodical health examinations
– Environmental changes
– Provision of safe water
– Sanitary latrines
– Insect and rodent control
Specific Protection
Measures applicable to a disease or
group of diseases to intercept the cause
before the involvement
• Specific immunization -Communicable
• Specific Nutrient - Nutritional deficiency
• Dental carries — Fluoride
• Goiter – Iodine
• Protection against hazards Cancer–
• Chemoprophylaxis
Secondary Protection
Early diagnosis and prompt
• Patient comes in contact with
health worker or health facility
• Action which halts the progress of
a disease at its early stage and
prevent complication
• Arrest the disease process and
restore health
• TB- Skin and sputum test
Tertiary Prevention
• All measures to reduce or limit
impairments and disabilities, minimize
suffering from disease and to promote
the patients adjustment in society
Disability limitation
– limiting further progress of disability
– Measures of prevention at this level is
provision of therapeutic substances to
arrest the disease and prevent further
To train the individual to be useful member
Medical rehabilitation
Vocational rehabilitation
Social rehabilitation
Psychological rehabilitation
•Occupational therapy
•Speech therapy
•Social work
•Vocational guidance
•Placement services
Concepts of Control
• Disease control
• Disease Elimination
• Disease Eradication
Disease control
Aim is to reduce
– The incidence of disease
– The duration of disease
– The effects of infection
– The financial burden
Disease Elimination
Between control and eradication
INTERRUPTION of transmission of
Polio, Measles
Disease Eradication
– Tear out by roots
– Termination of all transmission of
infection by extermination of
infectious agent
– Small pox
Universal prevention
• Addresses the entire population (national,
local community, school, district)
• Aim to prevent or delay the abuse of
alcohol, tobacco, and other drugs.
• All individuals, without screening, are
provided with information and skills
necessary to prevent the problem.
Selective prevention
• focuses on groups whose risk of developing
problems of alcohol abuse or dependence is
above average.
The subgroups may be distinguished by
characteristics such as age, gender, family
history, or economic status.
For example, drug campaigns in recreational
Indicated prevention
• involves a screening process, and aims to
identify individuals who exhibit early signs of
substance abuse and other problem behaviors.
Identifiers may include falling grades among
students, known problem consumption or
conduct disorders, alienation from parents,
school, and positive peer groups etc.
• Prophylaxis " to guard or prevent beforehand
any medical or public health procedure whose
purpose is to prevent, rather than treat or cure a
• prophylactic measures
– primary prophylaxis (to prevent the
development of a disease)
– secondary prophylaxis (whereby the disease
has already developed and the patient is
protected against worsening of this process).
Prevention is better than cure
• Proverbial saying, 17th century
• This proverb is often used in relation to
health and disease.
• It's better to take care that a problem
does not happen than to have to solve the
problem afterwards.
• It's easier to stop something bad from
happening in the first place than to fix the
damage after it has happened.
Latin saying of 13th century
It is better and more useful to meet a
problem in time than to seek a
remedy after the damage is done.
Yesterday I was clever
so I wanted to change the
Yesterday I was clever
so I wanted to change the
Today I am wise
so I changed myself
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