a measure of association that quantifies the association between an exposure and a health outcome from an epidemiologic study, calculated as the ratio of incidence proportions of two groups.
an aspect of personal behavior or lifestyle, an environmental exposure, or a hereditary characteristic that is associated with an increase in the occurrence of a particular disease, injury, or other health condition.
the probability that an event will occur (e.g., that a person will be affected by, or die from, an illness, injury, or other health condition within a specified time or age span).
the habitat in which an infectious agent normally lives, grows, and multiplies, which can include humans, animals, or the environment.
a general term for measures of association calculated from the data in a two-by-two table, including risk ratio, rate ratio, and odds ratio.
in a line listing, each row is a record or observation. A record represents data related to a single case.
the relative size of two quantities, calculated by dividing one quantity by the other.
a measure of association that quantifies the relation between an exposure and a health outcome from an epidemiologic study, calculated as the ratio of incidence rates or mortality rates of two groups.
an expression of the relative frequency with which an event occurs among a defined population per unit of time, calculated as the number of new cases or deaths during a specified period divided by either person-time or the average (midinterval) population. In epidemiology, it is often used more casually to refer to proportions that are not truly rates (e.g., attack rate or case-fatality rate).
in statistics, the difference between the largest and smallest values in a distribution; in common use, the span of values from smallest to largest.
the separation of well persons who have been exposed or are suspected to have been exposed to a communicable disease, to monitor for illness and to prevent potential transmission of infection to susceptible persons during the incubation period. Quarantine refers to separation of potentially exposed but well persons; isolation refers to separation of ill persons.
the proportion of deaths among a population attributable to a particular cause during a selected period. Each cause of death is expressed as a percentage of all deaths, and the sum of the proportionate mortality for all causes must equal 100%. These proportions are
not mortality rates because, in proportionate mortality, the denominator is all deaths instead of the population among whom the deaths occurred.
a measure of the impact of a causative factor on the public health; the proportion of a health state or event among exposed persons that can be attributed to the
exposure also called attributable risk percent.
a 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), a fraction (1/5), or a percentage (20%).
a set of regulations based on the Health Insurance Portability and Accountability Act to protect the privacy of individually identifiable health information.
the amount of a particular disease, chronic condition, or type of injury present among a population at a single point in time.
the amount of a particular disease, chronic condition, or type of injury present among a population at any time during a particular period.
the proportion of a population that has a particular disease, injury, other health condition, or attribute at a specified point in time (point prevalence) or during a specified period (period prevalence).
the number or proportion of cases or events or attributes among a given population.
predictive value positive
the proportion of cases identified by a test, reported by a surveillance system, or classified by a case definition that are true cases, calculated as the number of true-positives divided by the number of true-positives plus false-positives.
portal of exit
a pathway by which an agent can leave its host.
portal of entry
a pathway into the host that gives an agent access to tissue that will allow it to multiply or act.
a graphical display of the age-sex distribution of a population, constructed with a horizontal histogram of the age distribution of males pointing to the left, and the corresponding horizontal histogram of age distribution of females pointing to the right.
the total number of inhabitants of a geographic area or the total number of persons in a particular group (e.g., the number of persons engaged in a certain occupation).
a circular graph of a frequency distribution in which each segment of the pie is proportional in size to the frequency of corresponding category.
a branching chart that indicates the evolutionary lineage or genetic relatedness of organisms.
the amount of time each participant in a cohort study is observed and disease-free, often summed to provide the denominator for a person-time rate.
the incidence rate calculated as the number of new cases among a population divided by the cumulative person-time of that population, usually expressed as the number of events per persons per unit of time.
a set of cut points used to divide a distribution or a set of ranked data into 100 parts of equal area with each interval between the points containing 1/100 or 1% of the observations. For example, the 5th percentile is a cut point with 5% of the observations below it and the remaining 95% above it.
the ability of an agent to cause disease after infection, measured as the proportion of persons infected by an agent who then experience clinical disease.
an epidemic occurring over a widespread area (multiple countries or continents) and usually affecting a substantial proportion of the population.
the probability of observing an association between two variables or a difference between two or more groups as large or larger than that observed, if the null hypothesis were true. Used in statistical testing to evaluate the plausibility of the null hypothesis (i.e., whether the
observed association or difference plausibly might have occurred by chance).
a value substantively or statistically different from all (or approximately all) of the other values in a distribution.
any or all of the possible results that can stem from exposure to a causal factor or from preventive or therapeutic interventions; all identified changes in health status that result from the handling of a health problem.
an outbreak that spreads from person to person rather than from a common source.
a common source outbreak in which the exposure period is relatively brief so that all cases occur within one incubation period.
an outbreak that results from persons being exposed to the same harmful influence (e.g., an infectious agent or toxin). The exposure period can be brief or can
extend over days, weeks, or longer, with the exposure being either intermittent or continuous.
the occurrence of more cases of disease, injury, or other health condition than expected in a given area or among a specific group of persons during a specific period. Usually, the cases are presumed to have a common cause or to be related to one another in some way. Sometimes distinguished from an epidemic as more localized, or the term less likely to evoke public panic.
a measure of association used in comparative studies, particularly case-control studies, that quantifies the association between an exposure and a health outcome; also called the cross-product ratio.