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56 terms

Epidemiological Terms

Definitions of terms from Disease Detectives
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Epidemiology
the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems
Frequency
relationship between the number of cases of disease and the size of the population
Pattern
occurrence of health-related events by time, place, and person
Determinants
causes and other factors that influence the occurrence of disease and other health-related events
Father of Epidemiology
John Snow
Public Health Surveillance
ongoing, systematic collection, analysis, interpretation, and dissemination of health data to help guide public health decision making and action
Effectiveness
ability of a program to produce the intended results in the field
Efficacy
the ability to produce results under the ideal conditions
Efficiency
ability of the program to produce the intended results minimum expenditure of time and resources
Case Definition
a set of standard criteria used for classifying whether a person has a particular disease, syndrome, or other health condition
Descriptive Epidemiology
Type of epidemiology which only covers time place and time to describe an outbreak rather than case definition, person, place, time, and causes/risk factors/modes of transmission
Analytic Epidemiology
The type of epidemiology turned to to test hypotheses formed with information acquired through descriptive epidemiology
Experimental studies
Form of analytic epidemiology which tests hypotheses in a very controlled environment
Observational studies
Type of analytic study in which the epidemiologist simply observes the exposure and disease status of each participant. (Cohort, case-control, and cross-sectional)
Cohort Study
Epidemiologist tracks whether or not the participant is exposed and then tracks them to see if they develop the disease. It is the most reliable form of analytic study, but most expensive and time-consuming.
prospective study
A study which monitors exposure first, then looks forward to see if disease is developed.
retrospective study
starts with people already diseased, then traces back to see if they had been exposed
Case-control study
enroll people with disease and use people without the disease. they then compare previous exposures between the two groups
cross-sectional study
the least expensive and least effective analytic study
Epidemiological triad
agent host environment
agent
A microbe which causes disease
Host
the human who develops the disease
environment
extrinsic factors that affect the agent and the opportunity for exposure
Incubation period
the stage of subclinical disease extending from the time of exposure to onset of disease symptoms for infectious diseases
Latency period
the stage of subclinical disease extending from the time of exposure to onset of disease symptoms for chronic disease
Spectrum of disease
the disease process resulting in illness which is mild, severe, or fatal and eventually ends in recovery, disability, or death
Infectivity
the proportion of exposed persons who become infected
pathogenicity
the proportion of infected individuals who develop clinically apparent disease
virulence
the proportion of clinically apparent cases that are severe or fatal
carriers
persons who are infectious but have subclinical disease
reservoir
the habitat in which the agent normally lives, grows, and multiplies
portal of exit
the path by which a pathogen leaves its host
mode of transmission
the way through which an agent is transmitted to its host
portal of entry
the manner in which the pathogen enters a susceptible host
direct transmission
an infectious agent is transferred from a reservoir
direct contact
skin to skin contact
droplet spread
spray with relatively large, short-range aerosols produced by sneezing, coughing, or even talking
indirect transmission
the transfer of an infectious agent from a reservoir to a host by suspended air particles, inanimate objects, or vectors
airborne
transmission occurs when infectious agents are carried by dust or droplet nuclei suspended in air
herd immunity
suggests that if a high enough proportion of individuals in a population are resistant to an agent, then those few who are susceptible will be protected by the resistant majority since the pathogen will be unlikely to "find those few susceptible individuals
endemic level
the amount of a particular disease that is usually present in the community
sporadic
a disease that occurs infrequently and irregularly
endemic
the constant presence and or usual prevalence of a disease or infectious agent in a population within a geographic area
common source outbreak
an outbreak in which a group of persons are all exposed to an infectious agent or toxin from the same source
point source outbreak
if the group is exposed over a relatively brief period, so everyone who becomes ill does so in on incubation period, then the common source outbreak is further classified as a point source outbreak
continuous common-source outbreak
common source outbreaks in which patients have been exposed over a period of days, weeks, or longer
intermittent common-source outbreak
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propagated outbreak
results from transmission from one person to another
mixed epidemics
an epidemic with features of both a common-source outbreak and a propagated outbreak
ratio
the relative magnitude of two quantities or a comparison of any two values
proportion
the comparison of a part to the whole
rate
a measure of the frequency with which an event occurs in a defined population over a specified period of time
incidence rate
conveys a sense of speed with which disease occurs in a population, and seems to imply that this pattern has occurred and will continue to occur for the foreseeable future
attack rate
the proportion of the population that develops illness during an outbreak
case fatality rate
the proportion of persons with the disease who die from it
prevalence rate
the proportion of the population that has a health condition at a point in time