Epidemiology Glossary Part 2

grasshopper's version from 2017-03-26 02:03

Section 1

Question Answer
immunity, passiveImmunity conferred by an antibody produced in another host and acquired naturally by an infant from its mother or artificially by administration of an antibody-containing preparation (antiserum or immune globulin).
incidence rateA measure of the frequency with which an event, such as a new case of illness, occurs in a population over a period of time. The denominator is the population at risk; the numerator is the number of new cases occurring during a given time period.
incubation periodA period of subclinical or inapparent pathologic changes following exposure, ending with the onset of symptoms of infectious disease.
independent variableAn exposure, risk factor, or other characteristic being observed or measured that is hypothesized to influence an event or manifestation (the dependent variable).
indirect transmissionThe transmission of an agent carried from a reservoir to a susceptible host by suspended air particles or by animate (vector) or inanimate (vehicle) intermediaries.
individual dataData that have not been put into a frequency distribution or rank ordered.
infectivityThe proportion of persons exposed to a causative agent who become infected by an infectious disease.
inference, statisticalIn statistics, the development of generalizations from sample data, usually with calculated degrees of uncertainty.
interquartile rangeThe central portion of a distribution, calculated as the difference between the third quartile and the first quartile; this range includes about one-half of the observations in the set, leaving one-quarter of the observations on each side.
latency periodA period of subclinical or inapparent pathologic changes following exposure, ending with the onset of symptoms of chronic disease.
mean, arithmeticThe measure of central location commonly called the average. It is calculated by adding together all the individual values in a group of measurements and dividing by the number of values in the group.
mean, geometricThe mean or average of a set of data measured on a logarithmic scale.
measure of central locationA central value that best represents a distribution of data. Measures of central location include the mean, median, and mode. Also called the measure of central tendency.

Section 2

Question Answer
measure of dispersionA measure of the spread of a distribution out from its central value. Measures of dispersion used in epidemiology include the interquartile range, variance, and the standard deviation.
medianThe measure of central location which divides a set of data into two equal parts.
medical surveillanceThe monitoring of potentially exposed individuals to detect early symptoms of disease.
midrangeThe halfway point or midpoint in a set of observations. For most types of data, it is calculated as the sum of the smallest observation and the largest observation, divided by two. For age data, one is added to the numerator. The midrange is usually calculated as an intermediate step in determining other measures.
modeA measure of central location, the most frequently occurring value in a set of observations.
A measure of central location, the most frequently occurring value in a set of observations.Any departure, subjective or objective, from a state of physiological or psychological well-being.
mortality rateA measure of the frequency of occurrence of death in a defined population during a specified interval of time.
mortality rate, infantA ratio expressing the # of deaths among children under one year of age reported during a given time period divided by the number of births reported during the same time period. The infant mortality rate is usually expressed per 1,000 live births.
mortality rate, neonatalA ratio expressing the # of deaths among children from birth up to but not including 28 days of age divided by the number of live births reported during the same time period. The neonatal mortality rate is usually expressed per 1,000 live births.
mortality rate, postneonatalA ratio expressing the # of deaths among children from 28 days up to but not including 1 year of age during a given time period divided by the number of lives births reported during the same time period. The postneonatal mortality rate is usually expressed per 1,000 live births.
natural history of diseaseThe temporal course of disease from onset (inception) to resolution.
necessary causeA causal factor whose presence is required for the occurrence of the effect (of disease).
nominal scaleClassification into unordered qualitative categories; e.g., race, religion, and country of birth as measurements of individual attributes are purely nominal scales, as there is no inherent order to their categories.
normal curveA bell-shaped curve that results when a normal distribution is graphed.
normal distributionThe symmetrical clustering of values around a central location. The properties of a normal distribution include the following: (1) It is a continuous, symmetrical distribution; both tails extend to infinity; (2) the arithmetic mean, mode, and median are identical; and, (3) its shape is completely determined by the mean and standard deviation.
numeratorThe upper portion of a fraction.

Section 3

Question Answer
observational studyEpi study in situations where nature is allowed to take its course. Changes or differences in one characteristic are studied in relation to changes or differences in others, without the intervention of the investigator.
odds ratioA measure of association which quantifies the relationship between an exposure and health outcome from a comparative study; also known as the cross-product ratio.
ordinal scaleClassification into ordered qualitative categories; e.g., social class (I, II, III, etc.), where the values have a distinct order, but their categories are qualitative in that there is no natural (numerical) distance between their positive values.
outbreakSynonymous with epidemic. Sometimes the preferred word, as it may escape sensationalism associated with the word epidemic. Alternatively, a localized as opposed to generalized epidemic.
pandemicAn epidemic occurring over a very wide area (several countries or continents) and usually affecting a large proportion of the population.
pathogenicityThe proportion of persons infected, after exposure to a causative agent, who then develop clinical disease.
percentileThe set of numbers from 0 to 100 that divide a distribution into 100 parts of equal area, or divide a set of ranked data into 100 class intervals with each interval containing 1/100 of the observations. A particular percentile, say the 5th percentile, is a cut point with 5 percent of the observations below it and the remaining 95% of the observations above it.
period prevalenceThe amount a particular disease present in a population over a period of time.
person-time rateA measure of the incidence rate of an event, e.g., a disease or death, in a population at risk over an observed period to time, that directly incorporates time into the denominator.
pie chartA circular chart in which the size of each ``slice'' is proportional to the frequency of each category of a variable.
point prevalenceThe amount of a particular disease present in a population at a single point in time.
populationThe total # of inhabitants of a given area or country. In sampling, the population may refer to the units from which the sample is drawn, not necessarily the total population of people.
predictive value positiveA measure of the predictive value of a reported case or epidemic; the proportion of cases reported by a surveillance system or classified by a case definition which are true cases.
prevalenceThe # or proportion of cases or events or conditions in a given population.
prevalence rateThe proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specified period of time.

Section 4

Question Answer
propagated outbreakAn outbreak that does not have a common source, but instead spreads from person to person.
proportionA type of ratio in which the numerator is included in the denominator. The ratio of a part to the whole, expressed as a ``decimal fraction'' (e.g., 0.2), as a fraction (1/5), or, loosely, as a percentage (20%).
proportionate mortalityThe proportion of deaths in a specified population over a period of time attributable to different causes. Each cause is expressed as a percentage of all deaths, and the sum of the causes must add to 100%. These proportions are not mortality rates, since the denominator is all deaths, not the population in which the deaths occurred.
public health surveillanceThe systematic collection, analysis, interpretation, and dissemination of health data on an ongoing basis, to gain knowledge of the pattern of disease occurrence and potential in a community, in order to control and prevent disease in the community.
race-specific mortality rateA mortality rate limited to a specified racial group. Both numerator and denominator are limited to the specified group.
random sampleA sample derived by selecting individuals such that each individual has the same probability of selection.
rangeIn statistics, the difference between the largest and smallest values in a distribution. In common use, the span of values from smallest to largest.
rateAn expression of the frequency with which an event occurs in a defined population.
rate ratioA comparison of 2 grps in terms of incidence rates, person-time rates, or mortality rates.
ratioThe value obtained by dividing one quantity by another.
relative riskA comparison of the risk of some health-related event such as disease or death in two groups.
representative sampleA sample whose characteristics correspond to those of the original population or reference population.
reservoirThe habitat in which an infectious agent normally lives, grows and multiplies; reservoirs include human reservoirs, animals reservoirs, and environmental reservoirs.
riskThe probability that an event will occur, e.g. that an individual will become ill or die within a stated period of time or age.
risk factorAn aspect of personal behavior or lifestyle, an environmental exposure, or an inborn or inherited characteristic that is associated with an increased occurrence of disease or other health-related event or condition.

Section 5

Question Answer
sampleA selected subset of a pop. A sample may be random or non-random and it may be representative or non-representative.
scatter diagramA graph in which each dot represents paired values for two continuous variables, with the x-axis representing one variable and the y-axis representing the other; used to display the relationship between the two variables; also called a scattergram.
seasonalityChange in physiological status or in disease occurrence that conforms to a regular seasonal pattern.
secondary attack rateA measure of the frequency of new cases of a disease among the contacts of known cases.
secular trendChanges over a long period of time, generally years or decades.
sensitivityThe ability of a system to detect epidemics and other changes in disease occurrence. The proportion of persons with disease who are correctly identified by a screening test or case definition as having disease.
sentinel surveillanceA surveillance system in which a pre-arranged sample of reporting sources agrees to report all cases of one or more notifiable conditions.
sex-specific mortality rateA mortality rate among either males or females.
skewedA distribution that is asymmetrical.
specificityThe proportion of persons without disease who are correctly identified by a screening test or case definition as not having disease.
sporadicA disease that occurs infrequently and irregularly.
spot mapA map that indicates the location of each case of a rare disease or outbreak by a place that is potentially relevant to the health event being investigated, such as where each case lived or worked.
standard deviationThe most widely used measure of dispersion of a frequency distribution, equal to the positive square root of the variance.
standard error (of the mean)The standard deviation of a theoretical distribution of sample means about the true population mean.
sufficient causeA causal factor or collection of factors whose presence is always followed by the occurrence of the effect (of disease).
survival curveA curve that starts at 100% of the study population and shows the percentage of the population still surviving at successive times for as long as information is available. May be applied not only to survival as such, but also to the persistence of freedom from a disease, or complication or some other endpoint.

Section 6

Question Answer
tableA set of data arranged in rows and columns.
table shellA table that is complete except for the data.
transmission of infectionAny mode or mechanism by which an infectious agent is spread through the environment or to another person.
trendA long-term movement or change in frequency, usually upwards or downwards.
universal precautionsRecommendations issued by CDC to minimize the risk of transmission of bloodborne pathogens, particularly HIV and HBV, by health care and public safety workers. Barrier precautions are to be used to prevent exposure to blood and certain body fluids of all patients.
validityThe degree to which a measurement actually measures or detects what it is supposed to measure.
variableAny characteristic or attribute that can be measured.
varianceA measure of the dispersion shown by a set of observations, defined by the sum of the squares of deviations from the mean, divided by the number of degrees of freedom in the set of observations.
vectorAn animate intermediary in the indirect transmission of an agent that carries the agent from a reservoir to a susceptible host.
vehicleAn inanimate intermediary in the indirect transmission of an agent that carries the agent from a reservoir to a susceptible host.
virulenceThe proportion of persons with clinical disease, who after becoming infected, become severely ill or die.
vital statisticsSystematically tabulated information about births, marriages, divorces, and deaths, based on registration of these vital events.
years of potential life lostA measure of the impact of premature mortality on a population, calculated as the sum of the differences between some predetermined minimum or desired life span and the age of death for individuals who died earlier than that predetermined age.
zoonosesAn infectious disease that is transmissible under normal conditions from animals to humans.