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For other uses, see Epidemiology (disambiguation).
Epidemiology is the study (or the science of the study) of the patterns, causes, and effects of health and disease conditions in defined populations. It is the cornerstone of public health, and informs policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive medicine. Epidemiologists helpwith study design, collection and statistical analysis of data, and 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.[1]
Major areas of epidemiological study include disease etiology,outbreak investigation, disease surveillance and 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, andengineering for exposure assessment.
Contents  [hide] 
1 Etymology
2 History
2.1 Modern era
3 The profession
4 The practice
5 As causal inference
5.1 Bradford Hill criteria
5.2 Legal interpretation
6 Advocacy
7 Population-based health management
8 Types of studies
8.1 Case series
8.2 Case control studies
8.3 Cohort studies
8.4 Outbreak investigation
9 Validity: precision and bias
9.1Random error
9.2 Systematic error
9.2.1 Three types of bias
9.2.1.1 Selection bias
9.2.1.2 Information bias
9.2.1.3 Confounding
10 Journals
11 Areas
12 See also
13 References
13.1 Notes
13.2 Bibliography
14 External links
[edit]Etymology

Epidemiology, literally meaning "the study of what is upon the people", is derived from Greek epi, meaning "upon, among", demos, meaning "people,district", and logos, meaning "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).[2]
The distinction between "epidemic" and"endemic" was first drawn by Hippocrates,[3] to distinguish between diseases that are "visited upon" a population (epidemic) from those that "reside within" a population (endemic).[4] 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.[4] Epidemiologists also study the interaction of diseases ina population, a condition known as a syndemic.
The term epidemiology is now widely applied to cover the description and causation of not only epidemic disease, but of disease in general, and even many non-disease health-related conditions, such as high blood pressure and obesity. therefore this epidemiology is based upon how the pattern of the disease cause changes in the function of everyone.[edit]History

The Greek physician Hippocrates is known as the father of medicine, and was the first epidemiologist.[5][6] Hippocrates sought a logic to sickness; he is the first person known to have examined the relationships between the occurrence of disease and environmental influences.[7] Hippocrates believed sickness of the human body to be caused by an imbalance of the four Humors (air,fire, water and earth “atoms”). 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.[8] 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).[9]
Epidemiology is defined as the...