The Glossary of CDC's Principles of Epidemiology in Public Health Practice

active immunity

active immunity is your body's own immune system learning to fight a specific disease, either by fighting the real infection or through vaccination.

active surveillance

active surveillance is a proactive public health system where staff systematically contact healthcare providers or the public to actively seek out and gather data on health conditions to provide more accurate and timely information than passive methods.

age-adjusted mortality rate

A weighted average of age-specific death rates, using a standard population's age distribution (like the 2000 U.S. standard) to create a summary measure, allows fair comparison of mortality risk across different populations or over time by removing the influence of varying age structures.

agent

A factor (e.g., a microorganism or chemical substance) or form of energy whose presence, excessive presence, or in the case of deficiency diseases, relative absence is essential for the occurrence of a disease or other adverse health outcome.

age-specific mortality rate

The rate of death within a specific age group, calculated by dividing the number of deaths in that age group by the total population in that same age group, often expressed per 1000 or 100000 people to show risk for the particular age bracket.

alternative hypothesis

Complement to the null hypothesis, the alternate hypothesis is the statement that researchers are seeking to support through their investigation.

analytic epidemiology

Study focused on identifying and quantifying relationships between exposures (behaviors, genes, environment) and health outcomes using comparison groups to test how and why diseases occur.

analytic study

Tests hypotheses to quantify the relationship between an exposure and a health outcome, using comparison groups (really similar to the analytic epidemiology card lol)

antibody

Any of a variety of proteins in the blood that are produced in response to an antigen as an immune response.

antigen

Any substance (e.g., a toxin or the surface of a microorganism or transplanted organ) recognized as foreign by the human body and that stimulates the production of antibodies.

applied epidemiology

The practical application of epidemiological methods to control and prevent health problems in communities involving surveillance, field investigations, research, evaluation, and policy development to protect and improve public health.

arbovirus

Any of a group of viruses that are transmitted between hosts by mosquitoes, ticks, and other arthropods.

arithmetic mean

See mean, arithmetic.

arithmetic-scale line graph

See line graph, arithmetic-scale.

arthropod

An organism that has jointed appendages and segmented external skeleton (e.g., flies, mosquitoes, ticks, or mites).

association

The statistical relation between two or more events, characteristics, or other variables.

asymmetrical

A type of distribution where the shape to the right and left of the central location is not the same.

attack rate

A form of incidence that measures the proportion of persons in a population who experience an acute health event during a limited period.

attack rate, secondary

A measure of the frequency of new cases of a disease among the contacts of known patients.

attributable proportion

See proportion, attributable.

attributable risk percent

See proportion, attributable.

attribute

A risk factor that is an intrinsic characteristic of the individual person, animal, plant, or other type of organism under study.

axis

One of the dimensions of a graph in a rectangular graph, the x-axis is the horizontal axis, and the y-axis is the vertical axis.

bar chart

A visual display in which each category of a variable is represented by a bar or column.

bar chart, 100% component

A stacked bar chart in which all bars or columns are the same length, and the measured axis represents 0%-100%.

bar chart, deviation

A bar chart displaying either positive or negative differences from a baseline.

bar chart, grouped

A bar chart displaying quantities of two variables, represented by adjoining bars or columns of categories of one variable.

bar chart, stacked

A bar chart displaying quantities of two variables, represented by subdivided bars or columns.

cohort

A well-defined group of persons who have had a common experience or exposure and are then followed up, as in a cohort study or prospective study, to determine the incidence of new diseases or health events.

cohort, birth

A group of persons born during a particular period or year.

cohort study

See study, cohort.

common-source outbreak

See outbreak, common-source.

community immunity

See immunity, herd.

community trial

See trial, community.

comparison group

A group in an analytic study (e.g., a cohort or case-control study) with whom the primary group of interest is compared.

confidence interval

A range of values for a measure constructed so that the range has a specified probability of including the true value of the measure.

confidence limits

The end points (i.e., the minimum and maximum values) of a confidence interval.

confounding

The distortion of the association between an exposure and a health outcome by a third variable that is related to both.

contact

Exposure to a source of an infection; a person who has been exposed.

contact, direct

Exposure or transmission of an agent from a source to a susceptible host through touching.

contagious

Capable of being transmitted from one person to another by contact or close proximity.

contingency table

A two-variable table of cross-tabulated data.

control

In a case-control study, a member of the group of persons without the health problem under study.

crude

An overall or summary rate for a population, without adjustment.

cumulative frequency

The number or proportion of observations with a particular value and any smaller value.

cumulative frequency curve

A plot of the cumulative frequency rather than the actual frequency for each class interval of a variable.

death-to-case ratio

The number of deaths attributed to a particular disease divided by the number of new cases of that disease identified during the same period.

decision analysis

Application of quantitative methods to decision-making.

decision tree

A branching chart that represents the logical sequence or pathway of a clinical or public health decision.

demographic information

Personal characteristics of a person or group used in descriptive epidemiology to characterize patients or populations.

denominator

The lower portion of a fraction used in calculating a ratio, proportion, or rate.

determinant

Any factor that brings about change in a health condition or in other defined characteristics.

direct transmission

See transmission, direct.

distribution

The frequency and pattern of health-related characteristics and events in a population.

dose-response

Association between an exposure and health outcome that varies as the amount of exposure increases.

droplet nuclei

The residue of dried droplets of infectious agents that can remain suspended in air.

droplet spread

The direct transmission of an infectious agent by means of aerosols produced in sneezing, coughing, or talking.

effect

The result of a cause.

effectiveness

The ability of an intervention or program to produce the intended or expected results in the field.

efficacy

The ability of an intervention or program to produce the intended or expected results under ideal conditions.

efficiency

The ability of an intervention or program to produce the intended results with a minimum expenditure of time and resources.

EIS

Epidemic Intelligence Service; CDC's 2-year training program in applied epidemiology for public health professionals.

endemic

The constant presence of an agent or health condition within a given geographic area or population.

environmental factor

An extrinsic factor that affects an agent and the opportunity for exposure.

epidemic

The occurrence of more cases of disease than expected in a given area or among a specific group during a particular period.

epidemic curve

A histogram that displays the course of an outbreak or epidemic by plotting the number of cases according to time of onset.

epidemiologic triad

The traditional model of infectious disease causation having three components: an external agent, a susceptible host, and an environment.

epidemiology

The study of the distribution and determinants of health conditions or events among populations.

evaluation

Systematic and objective examination of activities to determine their relevance, effectiveness, and impact.

excess risk

Risk difference, calculated as the risk among the exposed group minus the risk among the unexposed group.

exposed group

A group whose members have had contact with a suspected cause of a particular health problem.

exposure

Having come into contact with a cause of a particular health problem.

false-negative

A negative test result for a person who actually has the condition.

false-positive

A positive test result for a person who actually does not have the condition.

fomite

An inanimate object that can be the vehicle for transmission of an infectious agent.

forest plot

A graph that displays the point estimates and confidence intervals of individual studies included in a meta-analysis or systematic review as a series of parallel lines.

frequency

The amount or number of occurrences of an attribute or health outcome among a population.

frequency distribution

A complete summary of the frequencies of the values or categories of a variable, often displayed in a two-column table with the individual values or categories in the left column and the number of observations in each category in the right column.

frequency polygon

A graph of a frequency distribution in which values of the variable are plotted on the horizontal axis, and the number of observations are plotted on the vertical axis. Data points are plotted at the midpoints of the intervals and are connected with straight lines.

geometric mean

See mean, geometric.

graph

A visual display of quantitative data arranged on a system of coordinates.

health

A state of complete physical, mental, and social well-being and not merely the absence of disease or other infirmity.

health indicator

Any of a variety of measures (e.g., mortality rate) that indicate the state of health of a given population.

health information system

A combination of health statistics from different sources. Data from these systems are used to learn about health status, health care, provision and use of services, and the impact of services and programs on health.

healthy worker effect

The observation that employed persons generally have lower mortality rates than the general population, because persons with severe, disabling disease (who have higher mortality rates) tend to be excluded from the workforce.

herd immunity

See immunity, herd.

high-risk group

A group of persons whose risk for a particular disease, injury, or other health condition is greater than that of the rest of their community or population.

HIPAA

The Health Insurance Portability and Accountability Act, enacted in 1996, which addresses the privacy of a person's medical information as well as postemployment insurance and other health-related concerns.

histogram

A visual representation of the frequency distribution of a continuous variable. The class intervals of the variable are grouped on a linear scale on the horizontal axis, and the class frequencies are grouped on the vertical axis.

host

A person or other living organism that is susceptible to or harbors an infectious agent under natural conditions.

host factor

An intrinsic factor (e.g., age, race/ethnicity, sex, or behaviors) that influences a person's exposure, susceptibility, or response to an agent.

hyperendemic

The constant presence at high incidence and prevalence of an agent or health condition within a given geographic area or population.

hypothesis

A supposition, arrived at from observation or reflection, that leads to refutable predictions; any conjecture cast in a form that will allow it to be tested and refuted.

hypothesis, alternative

The supposition that an exposure is associated with the health condition under study.

hypothesis, null

The supposition that two (or more) groups do not differ in the measure of interest (e.g., incidence or proportion exposed); the supposition that an exposure is not associated with the health condition under study.

immunity, active

Resistance developed in response to an antigen (i.e., an infecting agent or vaccine), usually characterized by the presence of antibody produced by the host.

immunity, herd

The resistance to an infectious agent of an entire group or community as a result of a substantial proportion of the population being immune to the agent.

immunity, passive

Immunity conferred by an antibody produced in another host. This type of immunity can be acquired naturally by an infant from its mother or artificially by administration of an antibody-containing preparation.

incidence

A measure of the frequency with which new cases of illness, injury, or other health condition occurs among a population during a specified period.

incidence proportion

The fraction of persons with new cases of illness, injury, or other health condition during a specified period.