A Novel Definition and Three-Stage Model for Health and Sickness
Dean D. Ad El

Abstract
Current definitions of health and sickness are too vague for application in bio models of disease processes. We propose a three-stage model identifying the boundary between the two states. Model Stage one is health, when multiple patho-physiological processes may occur but do not progress to disease due to host immunity. Stage two is subclinical disease, when pathophysiological processes may still be altered by medical diagnosis and treatment, and stage three is overt clinical disease. There is a critical threshold between the first and second stages at which the innate immunity is overcome, leading to the appearance of clinical symptoms. This model has important implications for interventional and preventive medicine.

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