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8:00 Physical agents : Heat, cold, radiation, noise, atmospheric pressure, humidity, etc. • Chemical agents : Endogenous: Urea, uric acid, bilirubin, ketones, calcium oxalate, etc. • Exogenous : Dust, das, fumes, metals, allergens, etc. • Biological agents : viruses, rickettsia, bacteria, fungi, protozoa, helminthes, etc. • Mechanical agents : friction, force, injuw, sprain, accidents, etc. • Nutritional agents : proteins, fats, II, Host Factors • Age : certain disease is peculiar in certain age-group. 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 anemia is more frequent among the Occupation : This not only determines the income but also the health hazards arising out ofthe occupation, e.g. pneumoconiosis • Literacy level : The higher the literacy level, the lower is the incidence Of the disease..

8:00 1. 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 I. Agent Factors • 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:.

8:00 • Income : This is the 'key' factors determining the standard Of living and influences the development of the disease. Lower socioeconomic status predisposes for infectious disease and higher status for non-communicable disease. Marital status : cancer of cervix is common among the married women than the unmarried women. • Nutritional status : poor nutritional status makes a person more vulnerable to infectious disease. • Life-style factors : Like smoking, alcoholism, drugabuse, lack of exercise, multiple sexual partnership, etc. favor the development of disease III. Environmental factors • These are classified into physical, biological, and sociological environment. Physical environment : Air, water, soil, food, etc. Plants, animals, insects, • Biological environment rodents, microbes, etc. • Sociological environment : death, divorce of parents, desertion, loss of employment, birth of a handicapped child, etc..

7:59 E. Epidemiological Triad : • The Germ theory of disease has many limitations. For example, it is well known that not everyone exposed to Tuberculosis develops tuberculosis. The same exposure, however in an undernourished or otherwise susceptible person, may result in clinical disease. Similarly, not everyone to beta-hemolytic streptococci develops Acute Rheumatic environment, which are equally important to determine whether or not disease will occur in the exposed host. This demanded a broader concept of disease that synthesized the basic factors of Agent, Host And Environment. Agent Disea Host se Envi onme.

8:00 F. Lazaru's theories of stress response • According to him, in the process of coping, the individual shapes as well as responds to a demand or stress, which can have an impact on the client's resistance to disease. G. Wolffs theory Ofstress, organ maladaptation and disease • He studied people's response to chronic stressors, like a frustrating job or an unhappy home life. He believed that a person's total life situation profoundly affects a person 's susceptibility to disease..

8:00 H. Holmes and rahe's theory of life changes and the onset of illness • They explored the relationship between the amount Of change in a person's life and subsequent illness. They discovered that the higher a person's life changes score, the greater is the like hood that an illness would develop. 2. PATHOGENESIS OF DISEASE • It means the evolution of a disease process in an individual, from its early stage to final stage of recovery Or death, in the absence Of any intervention such as prevention or treatment. This differs from disease and from person to person. • The natural history Of an infectious disease occurs in two phases pre-pathogenesis and pathogenesis..