This document discusses concepts related to disease, including definitions of disease, illness, and sickness. It covers concepts of causation from earlier theories to the germ theory and multifactorial causation. The natural history of disease and spectrum of disease are described. Risk factors, risk groups, and the iceberg model of disease are also summarized. The document concludes with concepts of disease control and monitoring.

2. 2
CONCEPT OF DISEASE
Dr Nabeela Basha
Seminar - 7

3. CONTENTS
 INTRODUCTION
 CONCEPTS OF DISEASE
 CONCEPTS OF CAUSATION
 NATURAL HISTORY OF DISEASE
 CONCEPTS OF CONTROL
 CONCEPTS OF PREVENTION
 CHANGING PATTERN OF DISEASE
 CONCLUSION
 REFERENCES
 PREVIOUS YEAR QUESTIONS
3

4. 4
• Disease the word itself has a negative vibe and recalls a
memory of suffering.
• Earlier disease was viewed as an curse or punishment for sins
committed by man i.e. it has its own fear factor.
• Later perceptions on disease were changed . It is now viewed
as a channel to explore more crevices in understanding human
body its capabilities, limitations, interactions etc.
• The concept of disease has been the subject of a vast, vivid
and versatile debate.

5. 5DEFINITIONS
“A condition in which body function is impaired, departure from a
state of health, an alteration of the human body interrupting the
performance of the vital functions.”
“The condition of body or some part of organ of body
in which its functions are disrupted or deranged.”
“Disease is considered a social phenomenon, occuring in all
societies and defined and fought in terms of the particular
cultural forces prevalent in the society.”
‘a maladjustment of human organism to the environment’

6. TO KEEP IT SIMPLE
Simplest definition – OPPOSITE TO HEALTH .
6
Any deviation from normal functioning or state of
complete physical or mental well-being.

7. DISEASE ILLNESS SICKNESS7
DISEASE
is a physiological/
psychological
dysfunction.
ILLNESS
is a subjective
state of the person
who feels aware
of not being well.
SICKNESS
is a state of social
dysfunction i.e. a
role that the
individual
assumes when ill
(sickness role).
Susser

8. 8
WHO has defined health but not disease,
because of the following limitations?
• Disease has got many shades(spectrum)
• Onset – acute or chronic
• Healthy outside infect others carriers…..

9. 9
• The same pathogen - more than one disease
(eg:streptococci).
• The same disease - more than one organism (e.g.
diarrhoea).
• The course of the disease may be short or prolonged
• It is difficult to demarcate between normal and
abnormal state as in hypertension, diabetes, mental
illness, etc.
• The final outcome of the disease isvariable, i.e.
recovery, disability or death.

10. SOCIAL SIGNIFICANCE
OF DISEASE
 Living with disease is very difficult.
 Disease has significant social or economic implications.
 Lepers - group of afflicted individuals, historically
shunned and the term "leper" still evokes social stigma.
Fear of disease can still be a widespread social
phenomena, though not all diseases evoke extreme social
stigma.
10

11.  Sickness confers the social legitimization of certain
benefits, such as illness benefits, work avoidance, and
being looked after by others.
 In return, there is an obligation on the sick person to seek
treatment and work to become well once more.
11

12.  As a comparison, consider pregnancy, which is not a state
interpreted as disease or sickness by the individual.
 On the other hand, it is considered by the medical
community as a condition requiring medical care and by
society at large as a condition requiring one's staying at
home from work.
12

13. Disease can be…….
 INFECTIOUS – resulting from infection.
 CONTAGIOUS –Transmitted through contact.
eg: scabies, trachoma, leprosy, STD.
 COMMUNICABLE – Illness due to specific infectious agent or
its toxic products capable of being directly or indirectly
transmitted from man to man, animal to animal or from
environment to man or animal (through air, dust, soil, water,
food, etc)
13

14.  ENDEMIC : (en: in , demos: people)
It refers to constant presence of a disease or infectious
agent with a given geographic area or population group,
without importation from outside.
eg: common cold.
 SPORADIC – Cases that occur irregularly, haphazardly
from time to time, and generally infrequently.
eg: Tetanus, herpes zoster, meningococcol meningitis.
14

15.  EPIDEMIC :
The unusual occurrence in a community or region, of
disease, specific health related behavior or other health
related events clearly in excess of normal expected
occurrence.
eg: MERS, Ebola virus disease, Typhus
15

16.  PANDEMIC – An epidemic usually affecting large
population, occurring over a wide geographic area such
as section of nation, the entire nation, a continent or the
world.
eg: influenza, cholera,
16

17. CONCEPT OF CAUSATION
Discovery of microbiology - turningpoint
 GERM THEORY OF DISEASE
 Microbes as sole cause of disease
17
EARLIER THEORIES
• Supernatural theory
• Theory of Humors
• Concept of contagion
• Miasmatic theory
• Theory of spontaneous generation
Contagion theory
Miasmatic theory

18. Limitations of Germ Theory
• Why only some people suffer from the
disease even after exposure
• Why certain people carry pathogens but
do not show manifestations of disease
• Why a disease would be epidemic
sometimes
• It does not take into account the multi-
factorial causation even in the diseases
in which micro-organism is the
“necessary cause”.
18

19. EPIDEMIOLOGICAL TRIAD 19

20. THE TETRAD OF EPIDEMIOLOGY 20
 Mission of epidemiology – break one of the legs of triangle
and disrupt the connection between these and thereby stopping
outbreak.

21. MULTIFACTORIAL CAUSATION
 CONCEPT- disease is due to multiple factors and not a
single one.
 PETTENKOFER OF MUNICH (1819-1901)-early
proponent of this concept. “Germ theory of disease "or
“single cause idea "in late 19th century overshadowed the
multiple cause theory.
21

22. 22
DISEASE
Other factors are responsible for disease…..
Socioeconomic factors.
Psychological factors.Cultural factors.
Genetic factors.

23. 23
Poor nutrition
Low immunity
Concurrent disease
Poverty
Overcrowding
malnutrition
Mycobacterium
tuberculi
Eg: TB

24. ADVANCED MODEL OF THE TRIANGLE
OF EPIDEMIOLOGY
24
Causative Factors
Groups or
populations and
their
characteristics
Environment
behaviour, culture
physiological factors
ecological elements
TIME

25. WEB OF CAUSATION
 Suggested by- Mac Mahon and Pugh.
 “Web of causation” considers all the predisposing factors of
any type and their complex interrelationship with each other.
Removal or elimination of just one link or chain may be
sufficient to control the disease, provided that link is
sufficiently important in the pathogenetic process.
25

26. Web of causation for Myocardial
Infarction
26

27. NATURAL HISTORY OF
DISEASE
27
 For successful prevention, control or eradication of
disease in community one should know the natural
history of the disease. Any disease has 2 phases
namely:-
1. Pre-pathogenesis phase
2. Pathogenesis phase

28. PRE PATHOGENESIS PHASE
• Disease agent has not entered man, but factors favouring disease
exist in the environment.
• What required is an interaction of these factors to initiate the
disease process.
Agent Host
Environment
28

29. PATHOGENESIS PHASE
 Entry of disease agent in susceptible human host.
 Disease agent multiplies and induces tissue and physiological
changes.
 Final outcome- recovery, disability or death.
 This phase may be modified by intervention measures such as
immunization, chemotherapy
29

30. 30

31. AGENT FACTORS 31
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.
1. Biological Agents – Infectivity Pathogenicity Virulence
2. Nutrient
3. Physical
4. Chemical
5. Mechanical
6. Absence or insufficiency
of a factor
7. Social

32. HOST FACTORS
 Human host - SOIL Disease agent – SEED
Classified as
 Demographic characteristics
 Biological characteristics
 Social & Economic
 Lifestyle factors
32

33. ENVIRONMENTAL FACTORS
 All that which is external to the individual human host,
living and non-living, and with which he is in constant
interaction.
-Macro-environment
 Physical
 Biological
 Psychosocial
33

34. RISK FACTORS
 Where the disease agent is not firmly
established, the aetiology is generally
discussed in terms of risk factors.
 The term risk factor is used by
different authors with at least two
meanings-
 An attribute or exposure that is
significantly associated with
development of disease.
 A determinant that can be modified
by intervention, thereby reducing the
possibility of occurrence of disease or
other specified outcomes.
34

35. 35
 Some risk factors can be modified while some cannot be
modified

36. RISK GROUPS
 Approach developed and promoted
by WHO is to identify precisely the
“risk groups” in the population by
certain defined criteria and direct
appropriate action to them first.
 This is known as the risk approach.
 Has been summed up as “something
for all, but more for those in need –
in proportion to the need.”
 Helps to define priorities and points
to those most in need of attention.
36

37. SPECTRUM OF DISEASE 37
 Is a graphic representation of variations in the
manifestations of disease.
 At one end are subclinical infections which are not
ordinarily identified and at the other end are fatal illnesses.
 In the middle of the spectrum lie illnesses ranging in
severity from mild to severe.

38. ICEBERG OF DISEASE
 Disease prevailing in the community may be compared to
the iceberg.
 The tip of the iceberg represents the clinical cases
prevailing in the community.
 The vast submerged portion of the iceberg represents the
hidden mass of disease in the community that is latent,
inapparent carriers.
38

39. 39
Symptomatic
disease; clinical
cases
Latent, inapparent,
presymptomatic and
undiagnosed cases
and carriers
What the
physician sees.
What the
physician does
not see.

40. CONCEPTS OF CONTROL
The term disease control refers ongoing operation aimed at
reducing:
 The incidence of disease.
 The duration of disease and the consequently the risk of
transmission.
 The effect of infection including physical and
psychological complication.
 The financial burden to the community.
40

41. Disease control includes… 41

42.  DISEASE MONITORING:
Defined as “the performance and analysis of routine
measurement aimed at detecting changes in the environment or
health status of population.” e.g. growth monitoring of child,
Monitoring of air pollution, monitoring of water quality etc.
 DISEASE SURVEILLANCE:
Defined as “the continuous scrutiny of the factors that
determine the occurrence and distribution of disease and other
conditions of ill health.”
42

43. What’s the difference?...
 Monitoring- requires careful planning, use of standardized
procedures and methods of data collection and can then be
carried over extended period of time by technicians and
automated instrumentation.
 Surveillance requires professional analysis, sophisticated
judgement of data leading to recommendation for control
activities
43

44. CONCEPTS OF PREVENTION
The goals of medicine are to
 Promote health,
 To preserve health,
 To restore health when it is
impaired
 And to minimize suffering and
distress.
44
These goals are embodied in the word "prevention"

45.  The concept of prevention is best defined in the context of
levels, traditionally called primary, secondary and tertiary
prevention. A fourth level, called primordial prevention, was
later added.
45

46. PRIMORDIAL PREVENTION
 DEFINITION
46
“It is the prevention of the emergence or development of
risk factors in countries or population groups in which they have
not yet appeared.”
 INTERVENTION
• The main intervention in
primordial prevention is through
individual and mass health education.

47. 2 approaches(WHO)-
A)Mass strategy-
Directed towards socio-economic, behavioural and lifestyle
changes
B) High-risk strategy
Aims to bring preventive care to individuals at special risk
47

48. PRIMARY PREVENTION
 Signifies intervention in the pre-pathogenesis phase of disease
or health problem.
 Relies on measures designed to promote health or to protect
against specific disease agents or hazards
 Applied to prevention of chronic diseases like CHD, HT ,
cancer based on elimination or modification of risk factors of
disease
48

49. SECONDARY PREVENTION
 Action which halts the progress of the disease at its incipient
stage and prevents complication
 Early diagnosis and treatment- arrest the disease process and
protect others in the community from acquiring the disease
 Health programs initiated by government are usually at this
level.
49

50. TERTIARY PREVENTION
 Signifies intervention at late pathogenesis stage.
 All measures available to reduce or limit impairment and
disabilities, minimise suffering caused by existing departure
from good health and to promote patient adjustment to
irremediable conditions.
 Through disability limitation and rehabilitation.
50

51. MODES OF INTERVENTION
 Intervention is any attempt to intervene or interrupt the
usual sequence in the development of disease.
 Five modes of intervention corresponding to the natural
history of any disease are:
 Health Promotion
 Specific Protection
 Early Diagnosis and Adequate Treatment
 Disability Limitation
 Rehabilitation
51

52. HEALTH PROMOTION
 It is the process of enabling people to increase control over
diseases, and to improve their health. It is not directed against
any particular disease but is intended to strengthen the host
through a variety of approaches(interventions):
52

53. SPECIFIC PROTECTION
Currently available interventions
1. Immunization
2. Use of specific nutrients
3. Chemoprophylaxis
4. Protection against occupational hazards
5. Protection against accidents
6. Protection from carcinogens
7. Avoidance of allergens
53

54. EARLY DIAGNOSIS AND
TREATMENT
WHO defined early detection of health impairment as “the
detection of disturbances of homeostatic and compensatory
mechanism while biochemical, morphological, and functional
changes are still reversible.”
Ex – essential hypertension, cancer of cervix and breast cancer
54

55. DISABILITY LIMITATION
 Objective- is to prevent or halt the transition of the disease process
from impairment to handicap.
Sequence of events leading to disability & handicap:
 Disease → Impairment → Disability→ Handicap.
WHO defined these terms-
 Impairment: Loss or abnormality of psychological,
physiological/anatomical structure or function.
 Disability: Any restriction or lack of ability to perform an activity in
a manner considered normal for one’s age, sex, etc.
 Handicap: Any disadvantage that prevents one from fulfilling his
role considered normal.
55

56.  “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”.
 Areas of concern in rehabilitation: medical, vocational,
social, psychological.
56REHABILITATION

57. CHANGING PATTERN OF
DISEASE
 Although diseases have not changed significantly through
human history, their patterns have.
 Every decade produces its own patterns of disease.
57

58. 58

59. DISEASE CLASSIFICATION
 A system of classification was needed whereby diseases
could be grouped according to certain common
characteristics , that would facilitate the statistical study of
disease phenomena.
 International classification of disease (ICD) by WHO -
accepted for national and international use.
 Revised once in 10 years.
59

60. ICD-10 ARRANGED IN 21 DIFFERENT
CHAPTERS
60

61. CONCLUSION
 Understanding disease pathology is the first step towards
formulating preventive measures.
 As a dentist or public health worker it is our primary
responsibility for the prevention of diseases in community
as well as individual.
61

62.  Park, Park’s Textbook of Preventive & Social Medicine,
23rd Edition, Jabalpur: Banarsidas Bhanot,2015.
 Soben Peter. Essentials of Public Health Dentistry. 4th ed.
New Delhi: Arya Publising House; 2013.
 Epidemiology, L. Gordis, Fourth ed, 2009, Saunders
 Gupta MC, Mahajan BK. Textbook of preventive and
social medicine 3rd Edition, Jaypee publishers,2003
62REFERENCES

63.  Hiremath S.S. Textbook of preventive and community
dentistry. 3rd ed. Elsevier publishers, New Delhi; 2016.
 www.who.int
 www.oraldiseaserisk.com
 www.googleimages.com
63

64. PREVIOUS YEAR QUESTIONS
 Epidemiological triad. [10 marks] RGUHS M.D.S.
DEGREE EXAMINATION
 Concepts of disease. [10 marks] RGUHS M.D.S.
DEGREE EXAMINATION 2004.
 Risk factors and risk groups. [7 marks] RGUHS M.D.S.
DEGREE EXAMINATION May 2012.
64

65. Thank You!