Epidemiology Terms

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Epidemiology Terms
2013-09-22 09:43:33
Epidemiology Terms

Terminology used in Vet Med Epidemiology
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  1. age-adjusted mortality rate
    A mortality rate statistically modified to eliminate the effect of different age distributions in the different populations.
  2. agent
    • A factor, such as a microorganism, chemical substance, or form of radiation, whose presence, excessive presence, or (in deficiency diseases) relative absence is essential for the
    • occurrence of a disease.
  3. age-specific mortality rate:
    • A mortality rate limited to a particular age group. The numerator is the number of deaths in that age group; the denominator is the number of persons in that age group in
    • the population.
  4. analytic epidemiology
    The aspect of epidemiology concerned with the search for health-related causes and effects. Uses comparison groups, which provide baseline data, to quantify the association between exposures and outcomes, and test hypotheses about causal relationships.
  5. analytic study
    A comparative study intended to identify and quantify associations, test hypotheses, and identify causes. Two common types are cohort study and case-control study.
  6. applied epidemiology
    The application or practice of epidemiology to address public health issues.
  7. association
    Statistical relationship between two or more events, characteristics, or other variables
  8. attack rate
    A variant of an incident rate, applied to a narrowly defined population observed for a limited period of time, such as during an epidemic.
  9. attributable proportion
    • A measure of the public health impact of a causative factor; proportion of a disease in a group that is exposed to a particular factor which can be attributed to their exposure to
    • that factor.
  10. bar chart
    A visual display of the size of the different categories of a variable. Each category or value of the variable is represented by a bar.
  11. bias
    Deviation of results or inferences from the truth, or processes leading to such systematic deviation. Any trend in the collection, analysis, interpretation, publication, or review of data that can lead to conclusions that are systematically different from the truth.
  12. biologic transmission
    The indirect vector-borne transmission of an infectious agent in which the agent undergoes biologic changes within the vector before being transmitted to a new host.
  13. 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).
  14. carrier
    • A person or animal without apparent disease who harbors a specific infectious agent and is capable of transmitting the agent to others. The carrier state may occur in an individual with an infection that is inapparent throughout its course (known as
    • asymptomatic carrier), or during the incubation period, convalescence, and postconvalescence of an individual with a clinically recognizable disease. The carrier state may be of short or long duration (transient carrier or chronic
    • carrier).
  15. case
    In epidemiology, a countable instance in the population or study group of a particular disease, health disorder, or condition under investigation. Sometimes, an individual with the particular disease.
  16. case-control study
    A type of observational analytic study. Enrollment into the study is based on presence (``case'') or absence (``control'') of disease. Characteristics such as previous exposure are then compared between cases and controls.
  17. case definition
    A set of standard criteria for deciding whether a person has a particular disease or health-related condition, by specifying clinical criteria and limitations on time, place, and person.
  18. case-fatality rate
    The proportion of persons with a particular condition (cases) who die from that condition. The denominator is the number of incident cases; the numerator is the number of cause-specific deaths among those cases.
  19. cause of disease
    A factor (characteristic, behavior, event, etc.) that directly influences the occurrence of disease. A reduction of the factor in the population should lead to a reduction in the occurrence of disease.
  20. cause-specific mortality rate
    The mortality rate from a specified cause for a population. The numerator is the number of deaths attributed to a specific cause during a specified time interval; the denominator is the size of the population at the midpoint of the time interval.
  21. census
    • The enumeration of an entire
    • population, usually with details being recorded on residence, age, sex,
    • occupation, ethnic group, marital status, birth history, and relationship to
    • head of household.
  22. chain of infection
    • A process that begins when an
    • agent leaves its reservoir or host through a portal of exit, and is conveyed by
    • some mode of transmission, then enters through an appropriate portal of entry
    • to infect a susceptible host.
  23. class interval
    • A span of values of a
    • continuous variable which are grouped into a single category for a frequency
    • distribution of that variable
  24. cluster
    An aggregation of cases of a disease or other health-related condition, particularly cancer and birth defects, which are closely grouped in time and place. The number of cases may or may not exceed the expected number; frequently the expected number is not known.
  25. cohort
    • A well-defined group of people who have had a common experience or exposure, who are then followed up for the incidence of new diseases or events, as in a cohort or prospective study. A
    • group of people born during a particular period or year is called a birth cohort.
  26. cohort study
    • A type of observational analytic study. Enrollment into the study is based on exposure
    • characteristics or membership in a group. Disease, death, or other health-related outcomes are then ascertained and compared.
  27. common source outbreak
    • An outbreak that results from a group of persons being exposed to a common noxious influence, such as an infectious agent or toxin. If the group is exposed over a relatively brief
    • period of time, so that all cases occur within one incubation period, then the common source outbreak is further classified as a point source outbreak. In some common source outbreaks, persons may be exposed over a period of days,
    • weeks, or longer, with the exposure being either intermittent or continuous.
  28. confidence interval
    A range of values for a variable of interest, e.g., a rate, constructed so that this range has a specified probability of including the true value of the variable. The specified probability is called the confidence level, and the end points of the confidence interval are called the confidence limits.
  29. confidence limit
    The minimum or maximum value of a confidence interval.
  30. contact
    Exposure to a source of an infection, or a person so exposed.
  31. contagious
    Capable of being transmitted from one person to another by contact or close proximity.
  32. contingency table
    A two-variable table with cross-tabulated data.
  33. control
    In a case-control study, comparison group of persons without disease.
  34. crude mortality rate
    The mortality rate from all causes of death for a population.
  35. cumulative frequency
    In a frequency distribution, the number or proportion of cases or events with a particular value or in a particular class interval, plus the total number or proportion of cases or events with smaller values of the variable.
  36. 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, quartiles, and other percentiles.
  37. death-to-case ratio
    The number of deaths attributed to a particular disease during a specified time period divided by the number of new cases of that disease identified during the same time period.
  38. demographic information
    • The "person'' characteristics--age, sex, race, and occupation--of descriptive epidemiology
    • used to characterize the populations at risk.
  39. Denominator
    The lower portion of a fraction used to calculate a rate or ratio. In a rate, the denominator is usually the population (or population experience, as in person-years, etc.) at risk.
  40. dependent variable
    In a statistical analysis, the outcome variable(s) or the variable(s) whose values are a function of other variable(s) (called independent variable(s) in the relationship under study).
  41. descriptive epidemiology
    descriptive epidemiology
  42. determinant
    Any factor, whether event, characteristic, or other definable entity, that brings about change in a health condition, or in other defined characteristics.
  43. direct transmission
    • The immediate transfer of an agent from a reservoir to a susceptible host by direct contact
    • or droplet spread.
  44. dot plot
    A visual display of the actual data points of a noncontinuous variable.
  45. distribution
    In epidemiology, the frequency and pattern of health-related characteristics and events in a population. In statistics, the observed or theoretical frequency of values of a variable.
  46. droplet nuclei
    The residue of dried droplets that may remain suspended in the air for long periods, may be blown over great distances, and are easily inhaled into the lungs and exhaled.