concepts of diseases

1. CONCEPTS OF
DISEASES
DR. MADHU S M

2. Definitions
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

3.  Illness : It is a subjective state of the person
who feels aware of not being well.
 Sickness : It is a state of social dysfunction.
 Disease : It is a physiological/ psychological
dysfunction.
 Carrier : A person with subclinical infectious
disease who can transmit the disease to
others is called a carrier.

4. Concepts of disease causation
Concepts
of disease
causation
Theories
Pathogenesis
of diseases
Iceberg
phenomenon

5. Theories of disease causation
1) Old theories (the ayurveda and the chinese
medicine )
2) Germ theory of disease
3) Biomedical model
4)Theory of multifactorial causation
5) Epidemiological triad

6.  Till the end of 18th century, various theories were in
vogue.
Ex : Supernatal theory of disease (eg- curse of god ;
an evil eye )
 The ayurveda considers that the disease is due to
imbalance of the ‘tridosha’
These are vata(air), pitta(bile) and kapha(mucus).
 The chinese medicine believes that the disease is
caused due to imbalance of male principle(yang)
and female principle(yin).
Imbalances of male principle(yang) are warm,
active, dry, sky and bright; female principle(yin) are
cool, rest, moist, earth and dark.
1) Old theories

7.  Germ theory of disease is based on the
concept that many disease are caused by
infections with microorganisms, typically
only visualized under high magnification.
 Such microoragnisms can consists of
bacterial, viral, fungal or protist species.
2) Germ theory of disease

8.  This model explains the disease as a result of
malfunctioning organs or cells.
 Ex : Diabetes is caused by malfunctioning of
pancreas.
 But the drawback with it is focuses on cause
and effect relationships, and ends to ignore
the psychological component of the disease.
3)The Biomedical model

9.  Now it is recognized that a disease is not caused by
an organism but also predisposed by many factors
contributing to its occurance, specially ‘Modern
Disease’ of civilization like lung cancer, diabetes,
coronary heart disease, mental illness etc.
 These predisposing factors are social, economic,
cultural, genetic psychological factors etc. ( including
poverty, illiteracy, ignorance and poor living
conditions).
 This theory of multifactorial causation was put
forward by Pettenkoffer Munich(1819-1901).This
theory deemphasizes the “ Germ theory” (or single
cause idea)
4)Theory of multifactorial causation

10. 5) Epidemiological triad
Epidemiologica
lTriad
Environment
Agent Host

11. 6)Web of causation

12. Natural history of disease

13. Natural history of disaese
PHASE - 1
Pre- pathogenesis phase
PHASE - 2
Pathogenesis phase

14. Prepathogenesis Phase
 This phase refers to the period before the
onset of disease. During this phase,
interaction is taking place among the three
components of epidemiological triad
namely agent, host and environment each…
 Disease agent has not entered man, but
factors favouring disease exist in the
environment.

15. PRE-PATHOGENESIS PHASE
HOST
ENVIRONMENT AGENT
Age, sex, race, genetic profile,
previous diseases, immune
status, religion, customs,
occupation, marital status,
family backgrounds
Temperature,
humidity,
altitude,
Crowding,
housing,
neighborhood,
Water, milk ,
food, radiation
Biologic- bacteria, viruses
Chemical-poison, alcohol,
smoke
Physical- trauma, radiation,
fire
Nutritional- lack, excess

16. 1) Agent factor
A disease ‘agent’ is defined as a substance, living or nonliving
or a force, the excessive presence or relative lack of which
initiates the disease process.The disease agents are
broadly classified into the following groups
Physical agents : heat, cold, radiation, noise, atmospheric
pressure, humidity etc.
Chemical agents :
Endogenous: Urea, uric acid, bilirubin, ketones, calcium
oxalate etc.
Exogenous : Dust, gas, fumes, metals, allergens etc.
Biological agents: viruses, rickettsia, bacteria, fungi,
protozoa, helminthes etc.
Mechanical agents: friction, force, injury, sprain, accidents
etc.
Nutritional agents: proteins, fats

17. 2) Host factors
Age : certain disease is peculiar in certain age
groups.
Gender : certain disease like lung cancer and
coronary heart disease are common among men
and rheumatoid arthritis, diabetes and obesity
are common among women.
Ethnicity : sickle cell anaemia is more frequent
among the negroes.
Occupation : This not only determines the income
but also the health hazards arising out of the
occupation. Ex- pneumoconiosis
Literacy level : The higher the literacy level, the
lower is the incidence of the disease.

18.  Income : This is the key factors determining the
standard of living and influences the
development of the disease. Lower
socioeconomic status predisposed for infectious
disease and higher status for non communicable
disease.
 Marital status : cancer cervix is common among
the married women than the unmarried women.
 Nutritional status : Poor nutritional status
makes a person more vulnerable to infectious
disease.
 Lifestyle factors : Like smoking, alcoholism,
drug abuse, lack of exercise, multiple sexual
partnership etc favour the development of
disease

19. 3 ) Environmental factors
 These are classified into physical, biological
and sociological environment.
 Physical environment: air, water, soil, food,
etc.
 Biological environment: plants, animals,
insects, rodents, microbes, etc.
 Sociological environment : death, divorce of
parents, desertion, loss of employment =,
birth of a handicapped child, etc.

20. 2. Pathogenesis phase
 The pathogenesis phase begins with the entry of the
disease ‘agent’ in the susceptible host.
 The further events in the pathogenesis phase are
clear cut in infectious disease, the disease agent
multiply and induces tissue and physiological
changes, the disease progresses through a period of
incubation and later through early and late
pathogenesis.
 The final outcome of disease may be recovery,
disability or death.
 The pathogenesis phase may be modified by
intervention measures such as immunization and
chemotherapy.

21. Exposure
Host
Disease
recovery
Disability
Death

22. cont..
 The infection may be clinical or sub clinical
and when it is subclinical, the person will not
have recognizable signs and symptoms nut
may spread the disease agent to others,
acting as a ‘carrier’ as in typhoid and
diphtheria.
 When the person develops clinical signs and
symptoms, he is called a ‘clinical case’.

23. Natural history of disease
Stage of susceptibility
Stage of prepathogenesis
Stage of clinical disease

24. 3) Iceberg phenomenon of disease
 According to this concept, the disease in the
community is compared to an iceberg.
 When a piece of ice is allowed to float on
water, a small portion is visible and a major
portion is submerged in the water.
 The visible tip of ice is compared to clinical
cases, which the physician sees in the
community.

25. Cont…
 The major submerged portion of ice
corresponds to the hidden mass of
unrecognized disease such as latent cases, in
apparent, carriers, asymptomatic, and
undiagnosed cases in the community, which
are all responsible for the constant
prevalence of the disease in the community.

27. Thank you

28. Concepts of control

29. Concept 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 effects of infection including physical and
psychological complication.
 The financial burden to the community.

30. Cont…
 Disease control includes…..
Control : public policy intervention that restricts the circulation of an infectious agent
beyond the level that would result from spontaneous, individual behaviours to
protect against infection.
Elimination: Reduction to zero of the incidence of a specified disease in a defined
geographical area as a result of deliberate efforts.
Eradication : termination of all transmission of infections by extermination of
infectious agents.
Extinction :The specific infectious agent no longer exists in nature or in the
laboratory

31. Disease monitoring:
 Defined as “the performance and analysis of routine
measurement aimed at detecting changes in the
environment or health status of population.”
 Ex: 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”.
 Ex: poliomyelitis surveillance programme ofWHO.

32. 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.

33. Concepts of prevention

34. Concepts of prevention
The goal of medicine are to
 Promote health
 To preserve health
 To restore health when it is impaired
 And to minimize suffering and distress.
These goals are embodied in the word “prevention”

35. Cont..
 Actions aimed at eradicating, eliminating or
minimizing the impact of disease and
disability, or if none of these are feasible,
retarding the progress of the disease and
disability.
 The concept of prevention is best defined in
the context of levels, traditionally called
primordial, primary, secondary and tertiary
prevention. A fourth level, called primordial
prevention, was later added.

36. Leavell’s levels of prevention
Stage of disease Level of prevention Type of response
Pre - disease Primary prevention Health promotion and
specific protection
Latent disease Secondary prevention Pre-symptomatic diagnosis
and treatment
Symptomatic disease Tertiary prevention •Disability limitation for
early symptomatic disease
•Rehabilitation for late
symptomatic disease

37. Primordial prevention
 Definition:
“ 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 is primordial prevention is through individual
and mass health education.
2 approaches (WHO) –
1) Mass strategy –
Directed towards socioeconomic, behavioural and lifestyle changes.
2) High risk strategy-
Aims to bring preventive care to individual at special risk.

38. Primary prevention
 Primary prevention can be defined as the action
taken prior to the onset of disease, which
removes the possibility that the disease will ever
occur.
 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.

39. Secondary prevention
 Action which halts the progress pf the at its
incipient stage and prevents complications.
 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.

40. 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.

41. Modes of
Intervention

42. 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

43. Health promotion
 It is the process of enabling people to
increase control over disease, 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):
 Health education
 Environmental modification
 Nutritional Intervention
 Lifestyle and behavioural changes

44. Specific protection
 Currently available interventions
 Immunization
 Use of specific nutrients
 Chemoprophylaxis
 Protection against occupational hazards
 Protection against accidents
 Protection from carcinogens
 Avoidance of allergens

45. 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 cervix and
breast cancer

46. Disability limitation
 Objective – Is to prevent or halt the transition
of the disease process from impairment to
handicap.
 Sequence of events leading to disability amd
handicap:
Disease
Impairment
Disability
Handicap

47.  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.

48. Rehabilitation
 “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.

49. Changing patterns of disease
 Although diseases have not changed
significantly through human history, their
patterns have.
 Every decade produces its own patterns of
disease.

50. 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.

51. ICD-10 arranged in 21
different chapters
 Major categories of the international classification of diseases and
related health problems(10th Revision)
 Certain infectious and parasitic diseases
 Neoplasms
 Diseases of the blood
 Endocrine, nutritional and metabolic disorders
 Mental and behavioural disorders
 Diseases of the nervous system
 Diseases of the eye and adnexa
 Diseases of the ear and mastoid process
 Diseases of the circulatory system
 Diseases of the respiratory system
 Diseases of the digestive system
 Diseases of the skin and subcutaneous tissue

52. Conclusion
 Understanding disease pathology is the first
step towards formulating preventive
measures.
 As a physiotherapist or public health worker it
is our primary responsibility for the
prevention of diseases in community as well
as individual.

53. Thank you