Glossary of Epidemiology Terms
Agent: A causative factor, such as a biological or chemical agent that must be present (or absent) in the environment for disease occurrence in a susceptible host.
Aggregate data: Data combined from several measurements or sets of measurements.
Analytic epidemiologic studies: Studies that examine groups of individuals in order to make comparisons and associations and to determine causal relationships; also known as cohort and case-control studies.
Bias: Any process or factor at any stage of a study from, its design to its execution to the application of information from the study, that produces results or conclusions that skew the results.
Case-control study: An analytic epidemiologic study design that assembles study groups after a disease has occurred; also called a retrospective study.
Cohort study: An analytic epidemiologic study type that assembles study groups before disease occurrence to observe and compare the rates of a health outcome over time; also called a prospective study.
Confounding factor: The distortion of the effect of one risk factor by the presence of another.
Correlation study: A descriptive epidemiologic study design used to compare aggregate populations for potential exposures of disease.
Cross- sectional survey: A descriptive epidemiologic study design that uses a representative sample of the population to collect information on current health status, personal characteristics, and potential risk factors or exposures at one point in time.
Descriptive epidemiologic studies: Epidemiologic study designs that contribute to the description of a disease or condition by examining the essential features of person, place, and time.
Environment: Internal and external factors that constitute the context for agent-host interactions; one's surroundings of any type.
Epidemic: A number of cases of an infectious agent or disease (outbreak) clearly in excess of the normally expected frequency of that disease in that population.
Exposure: The process by which an agent comes into contact with a person or animal in such a way that the person or animal may develop disease.
Incidence: The number of new cases of a disease diagnosed each year.