The basics of health and disease

What does healthy mean? Some would call it the absence of disease, or when a person can fully use all of his or her physical or mental capacities. But when what we understand as the concept of health is disrupted, in some way or another (which happens inevitably), we call it disease.

The study of the cause of this disease is what we call etiology and the field of etiological study can be specific, as in viral etiology or genetic etiology. Or, when the etiology of a disease is unknown, then idiopathic.

Unlike genetic etiology (think cystic fibrosis), which comes with a genetic structural or functional defect, congenital etiology has to do with factors affecting an embryo’s development in utero (think fetal alcohol syndrome).

The largest category of etiology is acquired disease. These are diseases that develop despite normal genes and embryonic development. Think everything else from tuberculosis to flu, to heart disease and cancer.

Diseases come with symptoms, signs or both. Signs are what is observable by another person – like clammy hands, fever, or irregular pulse. Symptoms are those that are found through physical examination with lab tests, x-rays, surgery.

When there’s a combination of signs and symptoms associated with a disease, we call it a syndrome (as in metabolic syndrome, Down’s syndrome).

After an examination of signs and symptoms, the pattern of development of the disease is pathogenesis. The pathogenesis could describer some kind of initial impact that produced the disease. The resulting condition is a sequela. If the pathogenesis had a rapid onset, it’s acute, and if it develops over time of months or years, then it’s chronic. When pathogenesis involves minor changes, the onset is said to be insidious.

The diagnosis, or identification, of a disease happens (or should happen) after a complete analysis of signs and symptoms with pathogenesis explained. Then, therapy follows with the goal of curing or reducing a patient’s signs or symptoms. The prognosis is the analysis of how a body responds to the therapy.


Nowak TJ, Hanfod AG. Pathophysiology: Concepts and applications for health care professionals, 3rd ed. 2004. New York, McGraw-Hill.

Published by David Despain, MS, CFS

David is a science and health writer living on Long Island, New York. He's written for a variety of publications including Scientific American, Outside Online, the American Society for Nutrition's (ASN) Nutrition Notes Daily, and Institute of Food Technologists' (IFT) Food Technology magazine and Live! blog. He's also covered new findings reported at scientific meetings including Experimental Biology, AAAS, AOCS, CASW, Sigma Xi, IFT, and others on his personal blog "Evolving Health." David is also an active member of organizations including the National Association of Science Writers (NASW), the American Association for the Advancement of Science (AAAS), the American Society for Nutrition, the Institute of Food Technologists, and the National Audubon Society. David has a master's degree in human nutrition from the University of Bridgeport, and a bachelor's degree in English from University of Illinois at Springfield. He also earned his Certified Food Scientist credential from the Institute of Food Technologists.

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