Vocab Flashcards
Agent
A factor that is essential for a disease, chronic conditions, or injury to occur. Examples of agents include microorganisms, chemical substances, forms of radiation, and, in the case of injury, physical force. Agents can cause a health problem by either being introduced, being present in excess, or being present at deficient levels.
Antibody
Any of a variety of proteins in the blood that are generated to produce immunity against microorganisms or their toxins.
Association
The statistical relationship between two or more events, characteristics, or other variables.
Attack rate
A form of incidence that measures frequency of disease, chronic conditions, or injury in a particular population for a limited time, such as during an outbreak. In calculating attack rates, the numerator is the number of new cases of a health problem during an outbreak, and the denominator is the population at the beginning of the period.
Secondary Attack Rate
A measure of the frequency of new cases of a disease, chronic condition, or injury among the contacts of known case-patients.
Bar chart
A visual display in which each category of a variable is represented by a bar. Bar charts are used to show variations in size among categories.
Bias
A systematic deviation from the truth; any trend in the collection, analysis, interpretation, publication, or review of data that can lead to conclusions that are systematically different from the truth.
Box plot
A visual display that summarizes data using a “box and whiskers” format to show the minimum and maximum values (ends of the whiskers), interquartile range (length of the box), and median (line through the box).
Carrier
A person or animal who harbors the infectious agent for a disease and can transmit it to others, but does not show signs of the disease. A carrier may be asymptomatic (never show signs of the disease) or may show signs of the disease only during the incubation period, convalescence, or postconvalescence. The period of being a carrier may be short (a transient carrier) or long (a chronic carrier).
Case
An instance of a particular disease, chronic condition, or type of injury. A variety of criteria may be used to identify cases (See Case definition), and the epidemiologic definition of a case is not necessarily the same as the ordinary clinical definition.
Case-patient
A person in a case-control study who has the disease or health condition under investigation.
Case definition
A set of standard criteria for determining whether a person has a particular disease or health condition. A case definition specifies clinical criteria and details of time, place, and person.
Case-fatality rate
The proportion of people with a particular condition (case-patients) who die from that condition. In calculating case-fatality rates, the numerator is the number of people who die from the condition, and the denominator is the total number of people with the condition.
Cause of disease
A factor (characteristic, behavior, event, etc.) that directly influences the occurrence of a disease. Reducing such a factor in a population should reduce occurrence of the disease.
Census
The enumeration of an entire population, usually including details on residence, age, sex, occupation, ethnic group, marital status, birth history, and relationship to head of household.
Chain of infection
A process that begins when an agent leaves its source through a portal of exit, is conveyed by some mode of transmission, and then enters through an appropriate portal of entry to infect a susceptible host.
Class
A grouping of observations of values of a variable. Classes are created for convenience in analyzing frequency.
Class boundaries
The values determining the upper and lower limits of a class
Class interval
The span of values of a continuous variable that lies between the class boundaries.
Clinical criteria
The symptoms and features of a disease that would be detected by physician analysis.
Clinical disease
A disease that has been manifested by its symptoms and features
Cluster
An aggregation of cases of a disease or other health condition that are closely grouped in time and place. The number of cases may or may not exceed the number expected, and frequently the expected number is not known. Cases of cancer and birth defects are often investigated as clusters.
Cohort
A well-defined group of people 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 conditions.
Birth Cohort
A group of people born during a particular period or year
Confidence interval
A range of values for a variable
Confidence level
The proportion of similarly constructed confidence intervals that include the parameter of interest
Confidence limits
The end points (i.e., the minimum and maximum values) of a confidence interval.
Contact
Exposure to a source of an infection; a person so exposed
Contagious
Capable of being transmitted from one person to another by contact or close proximity.
Contingency table
A table of cross-tabulated data that allows for calculating associations. The 2-by-2 table, with cases tabulated by exposure and outcome, is the contingency table most commonly used in epidemiology.
Control
The group of people without the health problem under study in a case-control study; a person in that group. For controls, investigators choose people who are as similar as possible to the cases, but without the health problem under study. In a case-control study, the control group is compared with the case group to determine associations between exposures and outcomes and to test hypotheses.
Cumulative frequency
In a frequency distribution, the number or proportion of cases with a particular value or less.
Cumulative frequency curve
A plot of the cumulative frequency rather than the actual frequency for each class interval of a variable. This type of graph is useful for identifying medians and quartiles and other percentiles.
Death-to-case ratio
The number of deaths attributed to a particular disease, chronic condition, or type of injury during a specified period divided by the number of new cases of that disease or injury identified during the same period.
Demographic information
The personal characteristics of age, sex, race, residence, and occupation. Demographic information is used in descriptive epidemiology to define the population at risk.
Denominator
The lower portion of a fraction. Epidemiologists use fractions to calculate rates, or ratios. The denominator is usually the population at risk, although it may also be a measure, such as person-time, that quantifies the population’s exposure.
Determinant
Any factor that brings about change in a health condition or in other defined characteristics.
Distribution
The complete summary of the frequency and pattern of the values or categories of a measurement. In epidemiology, distribution is the frequency and pattern of health-related characteristics and events in a population.
Dot plot
A visual display of the specific data points of a variable
Droplet nuclei
The residue of dried droplets that is easily inhaled and exhaled and may remain suspended in air for long periods and be blown over great distances.
Droplet spread
The direct transmission of an infectious agent by means of the aerosols produced in sneezing, coughing, or talking.
Endemic health condition
A disease, chronic condition, or type of injury that is constantly present in a given geographic area or population group; may also refer to the usual prevalence of a disease or condition.
Environmental factor
An extrinsic factor, such as geology, climate, insects, sanitation, or health services, that affects an agent and the opportunity for exposure.
Epidemic
The occurrence of more cases of a particular type of disease, chronic condition, or injury than expected in a given area, or among a specific group of people, over a particular period of time.
Epidemic curve
A histogram that shows the course of an outbreak or epidemic by plotting the number of cases of a disease, chronic condition, or injury according to time of onset.
Epidemic period
The time span of an epidemic
Epidemiologic triad
The traditional model of infectious disease causation, which has three components: an external agent, a susceptible host , and an environment that brings the host and agent together so that disease occurs.
Epidemiology
The study of the distribution and determinants of health conditions or events in populations, and the application of this study to control health problems.
Analytic Epidemiology
The aspect of epidemiology concerned with why and how a health problem occurs. Analytic epidemiology uses comparison groups to provide baseline data so that associations between exposures outcomes can be quantified and hypotheses about the cause of the problem can be tested. Examples include cohort studies and case-control studies .
Applied Epidemiology
The application or practice of epidemiology to control and prevent health problems.
Descriptive Epidemiology
The aspect of epidemiology concerned with gathering, organizing, and summarizing data on “person” (Who is ill?), “time” (When did they become ill?), and “place” (Where could they have been exposed to the illness?). This information is then used to conduct analytic epidemiology.
Evaluation
Systematic and objective examination of activities to determine how relevant and effective they are.
Exposed group
A group whose members have had contact with a cause of, or possess a characteristic that is a determinant of, a particular health problem
Exposure
Coming into contact with a cause of, or possessing a characteristic that is a determinant of, a particular health problem.
Frequency
The amount, or number of occurrences, of a disease, chronic condition, injury, or other attribute or event in a population.
Frequency distribution
A complete summary of the frequencies of the values or categories of a variable. Frequency distribution is 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 a straight line.
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 people in a defined population.
Health information system
A combination of health statistics from various sources. Data from these systems is used to learn about health status, health care, provision and use of services, and the impact of services and programs on health.
High-risk group
A group of people whose risk for a particular disease, health condition, or type of injury is higher than that of the rest of their community or population.
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 on the vertical axis. Rectangles are drawn so that their bases equal the class intervals, and their heights correspond to the class frequencies.
Host
A person or other living organism that is susceptible to an infectious agent under natural conditions
Host factor
An intrinsic factor (e.g., age, race, sex, behaviors) that influences an individual’s exposure, susceptibility, or response to an agent.
Hyperendemic health problem
A disease, chronic condition, or type of injury that is constantly present at a high incidence and/or prevalence. Examples include diabetes among the Pima Indians in Arizona and Hepatitis B in China and elsewhere in Asia
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
alternative hypothesis
The supposition that an exposure is associated with the health condition under study. The alternative is adopted if the null hypothesis proves implausible.
Null hypothesis
The supposition that an exposure is not associated with the health condition under study. The null hypothesis is the basis for most parametric tests for statistical significance.
Active immunity
Resistance developed in response to an antigen (infecting agentor vaccine) and usually characterized by the presence of antibody produced by the host.
Herd Immunity
The resistance of a group to an infectious agent. This group resistance exists because a high proportion of people in the group are immune to the agent. Herd immunity is based on the number of people who are susceptible and the probability that they will come into contact with an infected person. By vaccinating large numbers of people in a population to protect them from smallpox, health officials used herd immunity to control and eradicate the disease.
Passive immunity
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 (antiserum or immune globulin).
Incidence
A rate that measures the frequency with which a health problem, such as a new injury or case of illness, occurs in a population. In calculating incidence, the numerator is the number of new cases occurring in the population during a given period of time, and the denominator is the total population at risk during that time.
Incubation period
The period following exposure, when pathologic changes are not apparent, and ending with the onset of symptoms of an infectious disease.
Individual data
Data that have not been put into a frequency distribution