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Essay on the concept of disease for studentsLISHA

Disease

It is defined as any deviation from normal functioning or state of complete physical or mental well-

being. Disease has several spectrum ranging from mild cases to severe illness. The end result(outcome) of a disease may be recovery, disability or death.

Concept of causation

Previously, the germ theory of disease was in vogue. !ccording to this, diseases were thought to bedue to specific germ or agent. "ow, the concept is that diseases occur due to multiple factors i.e.,agent, host and environment. These three factors for the epidemiological triad. #or e$ampletubercule occurs not merely due to the presence of tuberculosis bacilli% (agent). &ther factors li'epoverty, overcrowding, malnutrition etc. (environment) contribute to its occurrence. !lso it is 'nownthat multiple factors li'e e$cess of fat inta'e, smo'ing, lac' of physical e$ercise and obesity areinvolved in the causation of coronary heart disease If these factors are 'nown, diseases can becontrolled or prevented by eliminating these factors.

NATURAL HISTORY OF DISEASENatura history of disease

Diseases occur due to a comple$ interaction between host, agent and environment. "atural history ofdisease is the study of evolution of disease from the earliest stage of prepathogenesis to itstermination (in the form recovery, disability or death). very disease has its own natural history. utit need not be the same in all individuals. "atural history can be established by *ohort studies,*ross-sectional and +etrospective studies.

Phases

The natural history of disease consists of two phases

. Prepathogenesis - the process in the environment

. Pathogenesis - the process in man

Prepathogenesis

This is the phase before the onset of disease in man. The disease agent has not yet entered man utthe factors needed for its interaction with the human host are already present in the environment.Potentially, we are all in the prepathogenesis phase of many diseases.

En!iron"ent

The causative factors of disease are !/"T, 0&1T and "2I+&"3"T. These three factors arereferred as epidemiological triad. The mere presence of these three factors is not sufficient to initiatea disease. !n interaction of all these three factors is necessary to initiate the disease process. Inprepathogenesis phase, the disease agent is already present but it has not entered man.

#atho$enesis

This phase begins with the entry of disease agent into man (host). There is a certain interval of timebefore the onset of clinical signs and symptoms of the disease. This period is called incubationperiod. During this period the disease agent multiplies and induces tissue and physiological changes.

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Incubation period is followed by early prepathogenesis. During this period, the signs and symptomsare not clear-cut. This is followed by late pathogenesis when there are clear-cut signs and symptoms.The final outcome of the disease may be recovery, disability or death.

I"portance of natura history

ach disease has its own natural history% but it is not necessarily the same in all individuals. If thephase of natural history is 'nown, appropriate level of prevention can be applied.

DISEASE A%ENTS

The first lin' in the chain of disease transmission is the disease agent. The disease agent is defined asa living or non- living substance or the e$cessive presence or absence of a force which may initiate orperpetuate a disease process.

Disease agents may be broadly classified as

. iologic agents

. "utrient agents

4. Physical agents

5. *hemical agents

6. 3echanical agents

7. 1ocial agents

8. !bsence or e$cess of health factors.

. iologic agents They are living organisms such as bacteria, viruses, proto9oa and fungi.

. "utrient agents They are proteins, fats, carbohydrates, vitamins and minerals. !ny e$cess ordeficiency of these nutrients can result in diseases.

4. Physical agents They are e$posure to heat, cold, pressure, electricity, radiation etc.

5 *hemical agents They may be

a) e$ogenous (present outside) such as fumes, dusts, metals, gases, etc.

b) endogenous (produced in the body) such as urea, uric acid,

'etones etc.

6. 3echanical agents 2arious mechanical forces may result in in:uries (li'e crushing, tearing,sprains) and even in death.

7. 1ocial agents They are poverty, smo'ing, alcohol, drug abuse, unhealthy life-styles, socialisolation etc.

8. !bsence or e$cess of health factors $cess or lac' of hormones,nutrients etc can lead to a varietyof diseases.

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HOST

The human host is supposed to be soil and the disease agent as the seed. The host factors areclassified as

&' Demographic characteristics such as age se$ and ethnicity.

(' iological characteristics such as genetic factors, blood groups, en9ymes, immunological factorsetc.)' 1ocial and economic characteristics such as education, occupation, income, housing etc.*' ;ife-style factors such as nutrition, e$ercise, use of alcohol, drug abuse, smo'ing etc.EN+IRON,ENT

The environment in which man lives is an important factor in the causation of diseases. nvironmentis classified as

. Physical environment

. iological environment

4. Psychological environment.

. Physical environment It refers to non-living things and physical factors such as air, water, light,noise, radiation etc. !lteration of physical environment has produced problems such as air pollution,

water pollution, noise pollution, radiation ha9ards etc. !ll these pollutions produce a variety ofdiseases.

. iological environment These are the living things which surround man including man himself.;iving things such as bacteria, viruses, insects, rodents and animals produce a variety of diseases andalso transmit them. *ontrol of these biological environments can protect the health of an individualand community.

4. Psychological environment It includes culture, customs, habits, beliefs, attitudes, moral, religion,

education, lifestyles etc. These factors also have an impact on health. The principle of healtheducation is to change the attitude and false belief of people about diseases.