1. NATURAL HISTORY OF DISEASE
DR. VAIBHAV GUPTA
MPH 1st year Student
Dept. of community medicine
JSSMC
21/11/2012

2. Plan of presentation
 Introduction
 Phases
 Factors
 Risks groups
 Spectrum of disease
 Concepts of prevention
 Modes of intervention

3. Introduction
The natural course that a disease would take
when it has not been affected by any treatment
or any other intervention. It is of much
importance for all of us to understand the
natural course of human disease.

4. Phase
1.Prepathogenesis phase
The disease agent has not yet entered
man, but the factors which favour its
interaction with the human host are already
existing in the environment.

5. 2. Pathogenesis phase
The pathogenesis phase begins with the entry
of the disease “agent’’ in the susceptible human
host. The disease agent multiplies and induces
tissue and physiological changes, the disease
progresses through a period of incubation and
later through early and late pathogenesis .

7. Factors
1.Agent factors
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.

8. Contd…………
 Biological agents:
These are living agents of disease, viruses,
rickettsiae, fungi, bacteria, protozoa and metazoa.
These agents exhibit certain “host-related”
Biological properties such as:
 Infectivity:
This is the ability of an infectious agent to invade
and multiply in a host:

9. Cont…
 Pathogenicity : This is the ability to induce
clinically apparent illness..
 Virulence: the proportion of clinical cases
resulting in severe clinical manifestations

10. Nutrient agents:- These are proteins, fats,
carbohydrate, minerals and water. Any excess or
deficiency of the intake of nutritive elements may
result in nutritional disorders. e.g. Anaemia, goitre,
obesity and vitamin deficiencies are some of the
current nutritional problems in many countries.
Physical agents:-Exposure to excessive heat, cold,
humidity, pressure, radiation, electricity, sound.

11. Contd….
Chemical agents :-
o Endogenous: e. g. Ureamia, jaundice, ketosis.
o Exogenous : e. g. allergens, metals, fumes.
Mechanical agents:- Exposure of chronic friction
and other mechanical forces may result in crushing,
tearing, sprains, dislocations and even death.

12. Cont…..
Absence or insufficiency or excess of a factor
necessary to health
These may be:
(i) Chemical factors
(ii) Nutrient factors
(iii) chromosomal factors
(iv) Immunological factors.
 Social agents:- It is also necessary to consider agents of
disease. These are poverty, smoking, abuse of drugs and
alcohol, unhealthy lifestyles, social isolation, maternal
deprivation

13. 2 Host factors
The human host is referred to as “soil” and the
disease agent as “seed” . In some situations,
host factors play a major role in determining
the outcome of an individuals exposure to
infection.eg. Tuberculosis.
The host factors may be classified as;
 Demographic
 Biological

14. cont…
 Social and economic characteristics such as
socioeconomic status, education, occupation,
stress , marital status , housing, etc.
 Lifestyle factors such as personality traits ,
living habits, nutrition, physical exercise, use
of alcohol, drugs and smoking, behavioral
patterns.

15. 3 Environmental factors
For human beings the environment is not limited, as it
normally is for plants and animals, to a set of climatic
factors.
For Example, for man, social and economic
conditions are more important than the mean annual
temperature.

16. Cont….
 Physical
 Biological
 Psychosocial.
 Physical environment:
The term “physical environment” is applied
to non-living things and physical factors (e.g..
Air, water, soil, housing, climate, geography,
heat, light, noise, debris & radiation)

17. Cont….
 Biological environment:- The biological
environment is the universe of living things which
surrounds man, including man himself. The living
things are the viruses and other microbial agents,
insects, rodents animals and plants
 Psychosocial environment:- “Those factors
affecting personal health, health care and
community well-being that stem from the
psychosocial make-up of individuals and the
structure and functions of social groups.”

18. Risk factor
a. An attribute or exposure that is significantly
associated with the development of a disease.
b. A determinant that can be modified by
intervention, thereby reducing the possibility
of occurrence of disease or other specified
outcomes.

19. Risk groups
Biological situation:
• age group, e.g., infants (low birth weight),
toddlers, elderly
• sex, e.g., females in the reproductive age
period
• physiological state, e.g., pregnancy,
cholesterol level, high blood pressure
• genetic factors, e.g., family history of genetic
disorders

20. Cont…
b. Physical situation:
• Rural, urban slums
• Living conditions , overcrowding
• Environment: water supply, proximity to industries
c. Sociocultural and cultural situation:
• Social class
• Ethnic and cultural group
• Family disruption. Education, housing
• Customs, habits and behavior
• Lifestyles and attitudes
• Access to health services

21. Spectrum of disease
The term “spectrum of disease” is a graphic representation
of variations in the manifestations of disease.
Iceberg of disease
The floating tip of the iceberg represents what the physician
sees in the community, i.e., clinical cases. The cast
submerged portion of the iceberg represents the hidden
mass of disease, i.e., latent, inapparent, presymptomatic
and undiagnosed cases and carriers in the community.
The “waterline” represents the demarcation between
apparent and inapparent disease.

22. Symptomatic disease
( what the physician sees)
Pre-symptomatic disease
(what the physician does not see)

23. Concepts of prevention
1. Primordial prevention
2. Primary prevention
3. Secondary prevention
4. Tertiary prevention

24. 1. Primordial prevention
In primordial prevention, efforts are directed towards
discouraging children from adopting harmful lifestyles.
2. Primary prevention
“Action taken prior to the onset of disease which removes
the possibility that a disease will ever occur”.
The WHO has recommended the following approaches
for the primary prevention of chronic diseases where the
risk factors are established:
a. population (mass) strategy
b. high-risk strategy

25. Cont…
3. Secondary prevention
“Action which halts the progress of a disease at
its incipient stage and prevents complications.”
4. Tertiary prevention
“All measures available to reduce or limit
impairments and disabilities, minimize
suffering caused by existing departures from
good health and to promote the patient’s
adjustment to irremediable conditions.”

26. Modes of Intervention
1. Health promotion
2. Specific protection
3. Early diagnosis and treatment
4. Disability limitation
5. Rehabilitation

27. 1. Health promotion
“The process of enabling people to increase
control over, and to improve health.” it is not
directed against any particular disease , but is
intended to strengthen the host through a variety
of approaches. The well-known interventions in
this area are:
i. Health education
ii. Environmental modifications
iii. Nutritional interventions
iv. Lifestyle and behavioral changes

28. Cont…
2. Specific protection
To avoid disease altogether is the ideal but this is possible
only in a limited number of cases. The following are
some of the currently available interventions aimed at
specific protection:
(a) Immunization
(b) Use of specific nutrients
(c) Chemoprophylaxis
(d) Protection against occupational hazards
(e) Protection against accidents

29. Cont…
(f) Protection from carcinogens
(g) Avoidance of allergens
(h) The control of specific hazards in the
general environment, e.g., air pollution,
noise control.

30. Cont..
3. Early diagnosis and treatment
A WHO Expert committee defined early detection
of health impairment as “the detection of
disturbances of homoeostatic and compensatory
mechanism while biochemical, morphological,
and functional changes are still reversible.”
4.Disability limitation
When a patient reports late in the pathogenesis
phase, the mode of intervention is disability
limitation.

31. Cont..
Concept of disability
Disease Impairment Disability Handicap
The WHO has defined these terms as follows:
(i) Impairment
(ii) Disability
(iii) Handicap

32. 5. Rehabilitation
“The combined and coordinated use of medical, social,
educational and vocational measures for training and
retraining the individual to the highest possible level of
functional ability.”
The following areas of concern in rehabilitation have been
identified:
(a) Medical rehabilitation – restoration of function
(b) Vocational rehabilitation – restoration of the capacity to
earn a livelihood.
(c) Social rehabilitation – restoration of family and social
relationships
(d) Psychological rehabilitation – restoration of personal
dignity and confidence.

33. THANK YOU