Epidemiology Glossary

The difference in the rate of a condition between an exposed and unexposed population, representing the amount of disease that can be attributed to the exposure.

A group of nine principles proposed in 1965 to assess the strength of evidence for a causal relationship between an exposure and a disease, including temporality, strength, consistency, and biological gradient.

The proportion of individuals diagnosed with a specific disease who die from that disease within a specified time period, reflecting disease severity.

An observational analytic study that compares individuals with a specific disease (cases) to individuals without the disease (controls) with respect to prior exposures.

An observational analytic study in which a defined group of individuals is followed over time to determine the incidence of an outcome, comparing those exposed and unexposed to a factor of interest.

A mixing of effects where a third variable, associated with both the exposure and the outcome, distorts the observed association between them.

An error in interpretation that occurs when relationships observed at the group or aggregate level are incorrectly assumed to hold true at the individual level.

A situation in which the strength or direction of the association between an exposure and outcome varies according to the level of a third variable, reflecting real biological or social interaction.

The habitual, constant presence of a disease or infectious agent within a given geographic area or population group at a baseline level.

The occurrence of disease cases in a community or region in excess of what is normally expected for that time and place.

A form of indirect protection from infectious disease that occurs when a sufficient proportion of a population has become immune, thereby reducing the likelihood of infection for susceptible individuals.

The number or rate of new cases of a disease occurring in a specified population during a defined time period.

Systematic error due to inaccurate measurement or classification of exposure, outcome, or other study variables, including recall bias and misclassification.

The state of being diseased or the frequency of disease in a population, quantified through measures like incidence and prevalence rates.

The frequency of death in a defined population during a specified time interval, which can be expressed as crude, age-specific, or cause-specific rates.

The ratio of the odds of exposure in the case group to the odds of exposure in the control group, used as the primary measure of association in case-control studies.

An epidemic occurring over a very wide area, typically crossing international boundaries and affecting a large number of people across multiple continents.

The total number of existing cases of a disease or condition in a population at a specific point or period in time, including both new and pre-existing cases.

The expected number of secondary cases produced by a single infection in a completely susceptible population, quantifying the transmissibility of an infectious agent.

An experimental study design in which participants are randomly allocated to receive either the intervention or a control condition, minimizing confounding and providing strong evidence for causation.

The ratio of the probability of an event occurring in an exposed group to the probability in a non-exposed group, used as the primary measure of association in cohort studies.

A systematic error in a study resulting from the way participants are selected or retained, such that the study population does not accurately represent the target population.

The ability of a test to correctly identify individuals who have the disease, calculated as the proportion of true positives among all people with the disease.

The ability of a test to correctly identify individuals who do not have the disease, calculated as the proportion of true negatives among all people without the disease.

The ongoing systematic collection, analysis, interpretation, and dissemination of health data essential for the planning, implementation, and evaluation of public health practice.