THIS PRESENTATION HIGHLIGHTS ABOUT THE NATURAL EVOLUTION OF DISEASE IN THE NATURE. This focuses on how a disease start developing in a human body. It focuses on the pre- pathogenesis and pathogenesis phase of disease.

1. NATURAL HISTORY OF
DISEASE
PRESENTED BY FALAQ IKRAM
BHMS (2018-2024)
BAKSON HOMOEOPATHIC MEDICAL COLLEGE
EMAIL: drfalaqikram@gmail.com

2. DEFINITION
• NOD signifies 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.
• Best understood by cohort studies.
Stage of
Pre- patho-
genesis
Pre-symptomatic
stage
Clinically
manifest disease
Progress to a fatal termination
Remission and relapses
Regress spontaneously,
leading to recovery
Risk Factors Precursors Effect of Treatment Prognostic factor

3. PERIOD OF PRE- PATHOGENESIS
• It refers to the period preliminary to the onset of disease in man.
• It starts when the factors affecting the disease are present but the agent has not
yet entered the body.
• Also referred to as ‘MAN IN MIDST OF DISEASE’ or ‘MAN EXPOSED TO THE RISK
OF DISEASE’

4. HOST
ENVIRONMENT
Epidemiological triad interaction of these three factors are required to initiate the
disease process in man.

5. PHASE OF PATHOGENESIS
• This period begins with the entry of disease ‘agent’ in the susceptible human
host.
• In cases of infectious disease, agent multiplies and induces tissue and
physiological changes  disease progresses through a period of INCUBATION 
early and late pathogenesis  recovery, disability and death.
• EXPOSURE  HOST  DISEASE  RECOVERY, DISABILITY, DEATH.
• This stage may be modified by interventions such as immunization or
chemotherapy.
• In this stage, infection (clinical or subclinical), host (carrier or w/o clinical ds).

6. • In chronic ds, early pathogenesis stage is referred as pre- symptomatic phase.
• Pathologically changes are below the clinical horizon (wont be visible enough).
• Clinical stage begins when there are recognizable signs and symptoms.
• When signs and symptoms appear  ds stage is advanced enough ( stage of late
pathogenesis)
• CHRONIC DISEASE  PRE SYMPTOMATIC PHASE & SYMPTOMATIC PHASE (early
and late )

9. RISK FACTORS
• An attribute or exposure that is significantly associated with development of a
disease.
• A determinant that can be modified by intervention  reduces chances of
occurrence of ds or other specific conditions.
• They are observable or identifiable prior to the event they predict.
• Risk factors  1. truly causative 2. merely contributory 3. predictive
• Risk factors can be modifiable or unmodifiable factors.
• Helps in prevention and intervention.

10. SPECTRUM OF DISEASE
• Graphic representation of variations in manifestations of disease.
• This sequence can be interrupted by early diagnosis and treatment or by
preventive measures, which if introduced at a particular point will prevent or
retard the future development of disease.

11. Floating tip= what a
physician sees in a
community= clinical
cases
Water line= represent
demarcation between
apparent and
inapparent diseases.
Submerged portion=
hidden man of ds.
Latent cases, pre-
symptomatic cases,
undiagnosed cases
and carriers.

12. HAPPY LEARNING.