Natural History of Disease

Nishitha A7th term

Objectives

• Introduction• Phases• Epidemiological Triad• Factors causing disease: Agent, Environment, Host• Risk Factors• Risk groups• Spectrum of Disease• Iceberg of Diseases

FAQ’s in RGUHS

• Natural history of Disease with stages• Macroenvironment• Risk Factors in Disease• Epidemiological Triad• Iceberg Phenomenon• Spectrum of Disease

Introduction

• Natural history of disease refers to the progress of a disease process in an individual over time, in the absence of treatment or prevention.

• Key concept in Epidemiology• Each disease has its own, unique natural

history.

Phases of Disease

Disease Process

Pre-Pathogenesis Pathogenesis

Pre-Pathogenesis

• Period of disease before man is involved• Process of disease in the environment• Man in the Midst of disease• 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.

Epidemiologic triad

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 .

Agent

• A substance , living or non-living, or a force, the excessive presence or relative lack of which may initiate or perpetuate a disease process.

• May be a single agent/combination of 2 independent agents

Types of Agents

Agents

Biological Nutrient Physical Chemical Mechanical Social

Biological Agents

Nutrient Agents

Physical Agents

Chemical Agents

Endogenous Exogenous

Social Agents

Host factors

Host Factors

Demographic

Biological

Socio-economic

Lifestyle

Host Factors

Environmental Factors

Environment

Physical Social Psychosocial

Macro-environment

All that which is external to the individual human host, living and non-living, and with which he is in

constant interaction.

Physical Enviroment

Biological Environment

Psychosocial Environment

Risk Factors

• Applicable to those diseases where the disease agent cannot be established.

• Definition : An attribute or exposure that is signifiantly associated with the development of a disease.

• Presence of a risk factor disease will occur• Absence of a risk factor absence of disease

Risk Factors- Types

ModifiableUnmodifiable

Risk Factors

Prominent Risk Factors- Heart Diseaes

Risk Groups

Spectrum of Disease

Spectrum of Disease

Iceberg Concept of Disease

References

• Park’s Textbook of Preventive & Social Medicine – 23rd Edition

• www.googleimages.com

Thank You