epidemiology epidemiology epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population. part of a series onpublic health outline subfields community health dental public health environmental health epidemiology health economics health education health promotion health policy health politics mental health occupational safety sexual and reproductive health sanitation world health (global health - international health) prevention disease surveillance health promotion (behavior change) health indicators lists and categories terminology journals national public health agencies medicine portal society portal it is a cornerstone of public health, and shapes policy decisions and evidence-based practice by identifying risk factors for disease and targets for preventive healthcare. epidemiologists help with study design, collection, and statistical analysis of data, amend interpretation and dissemination of results (including peer review and occasional systematic review). epidemiology has helped develop methodology used in clinical research, public health studies, and, to a lesser extent, basic research in the biological sciences. major areas of epidemiological study include disease causation, transmission, outbreak investigation, disease surveillance, environmental epidemiology, forensic epidemiology, occupational epidemiology, screening, biomonitoring, and comparisons of treatment effects such as in clinical trials. epidemiologists rely on other scientific disciplines like biology to better understand disease processes, statistics to make efficient use of the data and draw appropriate conclusions, social sciences to better understand proximate and distal causes, and engineering for exposure assessment. epidemiology, literally meaning "the study of what is upon the people", is derived from greek epi 'upon, among', demos 'people, district', and logos 'study, word, discourse', suggesting that it applies only to human populations. however, the term is widely used in studies of zoological populations (veterinary epidemiology), although the term "epizoology" is available, and it has also been applied to studies of plant populations (botanical or plant disease epidemiology). the distinction between "epidemic" and "endemic" was first drawn by hippocrates, to distinguish between diseases that are "visited upon" a population (epidemic) from those that "reside within" a population (endemic). the term "epidemiology" appears to have first been used to describe the study of epidemics in 1802 by the spanish physician villalba in epidemiología española. epidemiologists also study the interaction of diseases in a population, a condition known as a syndemic. the term epidemiology is now widely applied to cover the description and causation of not only epidemic, infectious disease, but of disease in general, including related conditions. some examples of topics examined through epidemiology include as high blood pressure, mental illness and obesity. therefore, this epidemiology is based upon how the pattern of the disease causes change in the function of human beings. history the greek physician hippocrates, known as the father of medicine, sought a logic to sickness; he is the first person known to have examined the relationships between the occurrence of disease and environmental influences. hippocrates believed sickness of the human body to be caused by an imbalance of the four humors (black bile, yellow bile, blood, and phlegm). the cure to the sickness was to remove or add the humor in question to balance the body. this belief led to the application of bloodletting and dieting in medicine. he coined the terms endemic (for diseases usually found in some places but not in others) and epidemic (for diseases that are seen at some times but not others). modern era