Epidemiology is the branch of medical science that investigates all the factors that determine the presence or absence of diseases and disorders. Epidemiological research helps us to understand how many people have a disease or disorder, if those numbers are changing, and how the disorder affects our society and our economy.

• Epidemiology is the study of how the disease is distributed in populations and the factors that influence or determine this distribution.
• It is defined as “the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control of health problems.”
• Information from epidemiologic studies frequently is used to plan new health services and to evaluate the overall health status of a given population.
• The field of epidemiology is highly interdisciplinary. In addition to its close ties to statistics, particularly biostatistics, it relies heavily on the concepts, knowledge, and theories of such disciplines as biology, pathology, and physiology in the health and biomedical sciences as well as on the disciplines of anthropology, psychology, and sociology in the behavioral and social sciences.

 Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in defined populations.

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 is the branch of medical science that investigates all the factors that determine the presence or absence of diseases and disorders. Epidemiological research helps us to understand how many people have a disease or disorder, if those numbers are changing, and how the disorder affects our society and our economy.