Basic Terms

• Epidemiology, public health, and health
• Epidemiology = the study of the distribution and determinants of disease and health-related states and events in specified populations, and the application of study results to control of health problems (Last, 2001).
• Public Health = organized community effort [activity] to prevent disease and promote health (Institute of Medicine, 1988).
• We can look at health from several perspectives. (Definitions may be personal and culturally specific). For example, 
• Health = the absence of disease (standard medical definition)
• Health = a state of physical, mental, and social well-being (WHO definition)
• Health = a continuum of wellness, which includes many different components (e.g., physical, mental, social, spiritual).
• From a social medicine perspective, we may distinguish between:
• Disease - a physiological or mental dysfunction.
• Illness - disease as experienced by the patient.
• Sickness - a state of social dysfunction (e.g., the inability to go to work).
• For the sake of uniformity of language, we will use the term disease (abbreviated "D") to refer to any  health-related state or event (including disease, injury, disabilities, and death).
• Epidemiologists study disease occurrences in all forms, including epidemics (disease occurrences in excess of normalcy), pandemics (epidemics affecting several countries or continents), and endemics (constant, normal, or expected level of disease).
• Epidemiologists study morbidity (disease or disability) and mortality (death). They also study the natural history of disease, and outcomes of treatments and interventions intended to improve health.
• The only effective way to control diseases is to understand its cause. Thus, epidemiologists continually address disease causality, studying causality in whatever manner seems likely to shed light on disease occurrence and prevention. This includes consideration of incidence and prevalence, studies of pathophysiology and psychology. Epidemiology borrows from many different disciplines, including biology, demography, sociology, psychology, mathematics and statistics, and the physical sciences--just to name a few .