Epidemiology Terms
Epidemiology studies how often diseases occur in populations, why, and how to control them. These terms cover the measures epidemiologists use, such as incidence, prevalence and the odds ratio, the main study designs, and how outbreaks spread and are stopped.
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- Basic reproduction numberEpidemiologyThe basic reproduction number, R0, is the average number of people one infectious person would infect in a population with no immunity.
- Body mass indexFood NutritionBody mass index is a screening measure that relates body weight to height, found by dividing weight in kilograms by height in meters squared.
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- Case fatality rateEpidemiologyThe case fatality rate is the share of people diagnosed with a particular disease who die of it, a basic measure of how severe that disease is.
- Case–control studyEpidemiologyA case–control study is an observational study that compares people with a disease and people without it to find past exposures linked to it.
- Cohort studyEpidemiologyA cohort study is an observational study that follows groups differing in an exposure over time to compare how often they develop an outcome.
- Communicable diseasePublic HealthA communicable disease is an infection that can pass from one person or animal to another, directly or through air, water, food, objects or vectors.
- ConfoundingEpidemiologyConfounding is a distortion in a study where a third factor, linked to both the exposure and the outcome, creates, hides or exaggerates an apparent effect.
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- EndemicEpidemiologyIn epidemiology, endemic describes a disease that is always found in a population or region at a fairly steady, expected level.
- EpidemicEpidemiologyAn epidemic is a rise in cases of a disease, often sudden, above the level normally expected in a given population, area and time.
- EpidemiologyEpidemiologyEpidemiology is the study of how often diseases and other health events occur in populations, what causes them and how they can be controlled.
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- IncidenceEpidemiologyIncidence is the number of new cases of a disease that arise in a population at risk during a specified period of time.
- Incubation periodEpidemiologyThe incubation period is the time between infection with a pathogen and the first appearance of signs or symptoms of the disease it causes.
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- MorbidityPublic HealthMorbidity is the state of having a disease, injury or disability, and also the amount of illness in a population, measured by incidence and prevalence.
- Mortality rateEpidemiologyA mortality rate is how often death occurs in a defined population over a set period, usually given as deaths per 1,000 or 100,000 people.
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- PandemicEpidemiologyA pandemic is an epidemic that crosses international borders and spreads over several continents, typically infecting very many people.
- PathogenMicrobiologyA pathogen is a microbe or other agent, such as a virus, bacterium, fungus, parasite or prion, that can cause disease in a host.
- PlaceboPharmacologyA placebo is an inactive treatment, such as a sugar pill or a sham procedure, made to look like a real one and used for comparison in clinical trials.
- PrevalenceEpidemiologyPrevalence is the share of a population living with a particular disease or condition, either at one point in time or across a set period.
- Public healthPublic HealthPublic health is the science and practice of preventing disease and injury and promoting health across whole communities rather than individual patients.
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- Randomized controlled trialEpidemiologyA randomized controlled trial is an experiment that assigns people by chance to a treatment or a comparison group to test whether the treatment works.
- Relative riskEpidemiologyRelative risk is the risk of an outcome in an exposed group divided by the risk in an unexposed group, showing how strongly the two are linked.
- Risk factorEpidemiologyA risk factor is a trait, exposure or behavior linked to a higher chance of developing a particular disease, injury or other health problem.
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- Selection biasEpidemiologySelection bias is an error that arises when the people recruited into, or remaining in, a study differ in systematic ways from the target population.
- SensitivityEpidemiologySensitivity is the proportion of people who truly have a condition whom a diagnostic or screening test correctly identifies as positive.
- Social determinants of healthPublic HealthSocial determinants of health are the nonmedical factors, such as income, education, housing and work, that shape a person's health throughout life.
- SpecificityEpidemiologySpecificity is the proportion of people who do not have a condition whom a diagnostic or screening test correctly identifies as negative.
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