disease detective vocab

Active immunity

Resistance developed by the body in response to an antigen (such as a pathogen or vaccine).

Age-adjusted mortality rate

A death rate statistically modified to eliminate the distorting effects of different age distributions.

Agent

An essential factor (microorganism, chemical, radiation, or physical force) required for a disease or injury to occur.

Age-specific mortality rate

A death rate calculated specifically for a distinct age group.

Alternative hypothesis

The statistical hypothesis stating that a significant relationship or difference exists between variables.

Analytic epidemiology

The branch of epidemiology that tests hypotheses to determine the causes and risks of health conditions.

Analytic study

A research study designed to examine associations, test hypotheses, and identify causes of health events.

Antibody

A blood protein produced by the immune system to destroy or neutralize specific microorganisms or toxins.

Applied epidemiology

The practical application of epidemiological methods to protect public health and control disease outbreaks.

Arithmetic mean

The average value calculated by adding all data points together and dividing by the total number of points.

Association

A statistical relationship or correlation connecting two or more events, traits, or variables.

Attack rate

The proportion of a population that develops a disease during a limited outbreak period.

Attack rate, secondary

The frequency of new disease cases occurring among the close contacts of known infected patients.

Attributable proportion

The fraction of a disease or health outcome that can be directly blamed on a specific exposure.

Bar chart

A visual graph using rectangular bars to compare the differences in size among different categories.

Bias

A systematic error or deviation from the truth in data collection, analysis, or interpretation.

Biologic transmission

Indirect vector-borne disease transfer where the agent undergoes biological changes or multiplies inside the vector.

Birth cohort

A group of individuals who were all born during the exact same year or time period.

Box plot

A visual diagram showing data distribution via its minimum, maximum, median, and interquartile range.

Carrier

An individual who harbors and transmits an infectious agent without showing any clinical symptoms.

Case

An individual instance of a particular disease, health condition, or injury.

Case-control study

A study comparing individuals with a condition (cases) to similar individuals without it (controls) to find past exposures.

Case-patient

A person selected for a study who explicitly has the disease or health condition being investigated.

Case definition

A standard set of clinical, time, place, and person criteria used to classify whether an individual has a condition.

Case-fatality rate

The proportion of individuals diagnosed with a specific condition who ultimately die from it.

Cause of disease

A specific factor, trait, or event that directly triggers the occurrence of a health condition.

Cause-specific mortality rate

A death rate calculated exclusively for a single, specific cause of death.

Census

A complete official count and demographic survey of an entire population.

Chain of infection

The step-by-step process of an agent leaving a source, being transmitted, and entering a new host.

Class

A grouped block of data values categorized together for easier frequency analysis.

Class boundaries

The specific minimum and maximum values that define the limits of a data group.

Class interval

The total span or range of continuous values contained within a single class boundary.

Clinical criteria

The physical symptoms and medical signs detected through a physician's formal examination.

Clinical disease

A disease status that has advanced enough to show clear, recognizable symptoms.

Clinical trial

An experimental study testing the safety and efficacy of medical interventions on human subjects.

Cluster

A noticeable aggregation of health cases closely grouped together in a specific time and place.

Cohort

A well-defined group of individuals sharing a common experience or exposure who are followed over time.

Common source outbreak

An epidemic where everyone is exposed to the exact same infectious or toxic source.

Community trial

An experimental study where an intervention is applied to an entire community or geographic population.

Confidence interval

A statistically calculated range of values likely to contain the true population parameter.

Confidence level

The probability that a calculated confidence interval actually contains the true target parameter.

Confidence limits

The exact upper and lower numerical endpoints of a confidence interval.

Contact

An individual who has experienced direct exposure to a source of infection.

Contagious

Capable of being transmitted directly from person to person through contact or close physical proximity.

Contingency table

A data table cross-tabulating exposures and outcomes, most commonly structured as a 2-by-2 matrix.

Continuous variable

A variable that can take on an infinite number of numerical values along a specific scale.

Control

The comparison group of individuals in a study who do not have the health condition being evaluated.

Crude mortality rate

The overall death rate for an entire population without adjusting for any demographic factors.

Cumulative frequency

A running total of the number or proportion of cases falling at or below a specific value.

Cumulative frequency curve

A graph plotting cumulative frequency against class intervals to easily locate medians and percentiles.

Death-to-case ratio

The total number of deaths from a condition divided by the number of new cases found in that same period.

Demographic information

Personal traits including age, sex, race, residence, and occupation used to define a population.

Denominator

The lower part of a fraction representing the total population at risk or total exposure time.

Dependent variable

The outcome variable being measured or predicted, which changes in response to an independent variable.

Descriptive epidemiology

The study of the distribution of health events by person, place, and time.

Determinant

Any physical, behavioral, or environmental factor that directly changes or brings about a health condition.

Direct transmission

The immediate transfer of an agent from a reservoir to a host via contact or droplet spray.

Discrete variable

A variable consisting of distinct, separate, countable values with no intermediate fractions.

Distribution

The structural pattern and frequency of health-related events and traits across a population.

Dot plot

A simple visual display where individual data points are plotted as dots along a single scale.

Droplet nuclei

Tiny dried residues of respiratory droplets that can remain suspended in the air for long periods.

Droplet spread

Direct transmission of an agent via short-range aerosols generated by sneezing, coughing, or talking.

Endemic health condition

A disease or injury that is constantly present at a baseline level in a specific geographic area.

Environmental factor

An external element (climate, geology, sanitation) that affects an agent and its odds of exposing a host.

Epidemic

An unexpected surge in the number of cases of a condition higher than what is normally anticipated.

Epidemic curve

A histogram showing an outbreak's progression by plotting case counts against their time of symptom onset.

Epidemic period

The total span of time over which an epidemic takes place.

Epidemiologic triad

The disease causation model consisting of an external agent, a susceptible host, and an environment.

Epidemiology

The study of how health conditions are distributed and determined in populations, applied to control health problems.