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Epidemiology > Unit 1 > Flashcards

Unit 1 Flashcards

1
Q

Epi

A

about or upon

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2
Q

Demos

A

populace or people

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3
Q

Logos

A

discoursing, writing, or talking about

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4
Q

Epidemiology

A

the study of disease in populations, with intention to institute control

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5
Q

List the 4 aims of epidemiology:

A

describe, explain, predict, control

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6
Q

We are not administering a fixed treatment, and we don’t control the exposure factor (temperature). We are not randomizing the animals.

A

Observational study

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7
Q

Principle type of epidemiologic study:

A

observational

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8
Q

What are the main types of observational studies?

A

cohort, case-control, and prevalence

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9
Q

What is action of primary care:

A

intended to prevent disease

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10
Q

What is the action of secondary care?

A

detect disease early with intention to reduce impact

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11
Q

What is the action of tertiary care?

A

extend/improve life after diagnosis

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12
Q

List the steps of the generalized disease pathway?

A

induction –> incubation period –> signs

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13
Q

Subjects are randomized to treatment, and receive specific treatments (randomization and control)

A

true experiments

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14
Q

Like a true experiment except no randomization (control without randomization)

A

quasi-experiments

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15
Q

Neither randomization nor control; subjects self select their treatment

A

observational studies

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16
Q

Measures of disease frequency:

A

rate, risk

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17
Q

What is the simplest measure of epidemiology?

A

count of cases

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18
Q

What type of frequency are we typically interested in?

A

relative frequency

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19
Q

Mathematically, what do we commonly use for measuring frequencies?

A

proportions, ratios, rates

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20
Q

What are the 2 ways to express incidence?

A
  • incidence rate (incidence density)

- cumulative incidence (risk, incidence proportion, attack rate)

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21
Q

A person can be an incident case only:

A

once

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22
Q

Indicates the movement from Well to Diseased:

A

Incidence

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23
Q

An expression to describe a change in one quantity with respect to another quantity with the denominator featuring a time component:

A

rate

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24
Q

Denominators for rates are in:

A

person-time/animal-time

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25
Q

What is the equation for incidence rate?

A

IR = (# new cases over a pd of time)/ (length of time at risk of developing disease)

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26
Q

When counting animal-time (time at risk), only count time of:

A

non-diseased animals

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27
Q

Count time for animals until:

A
  • animal gets disease
  • death from another cause
  • removed from herd
  • study terminates
  • intervention to render it non-susceptible
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28
Q

Proportion of non-disease individuals at the beginning of a period of study that become disease during the period:

A

simple cumulative incidence

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29
Q

means they can get the condition:

A

“at risk”

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30
Q

What’s the equation for cumulative incidence?

A

CI = (# of new cases over a period of time)/(number of healthy animals at beginning)

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31
Q

A cumulative incidence rate for an outbreak:

A

attack rate

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32
Q

When is it appropriate to measure attack rate?

A

when the exposure occurs in a very short and defined period of time

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33
Q

Attack rate =

A

(# of new cases)/(number of individuals exposed at the START)

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34
Q

Why is IR used less often than CI?

A

harder to interpret

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35
Q

IR is applicable to a group, while CI is applicable to:

A

a group or an individual

36
Q

What is incidence?

A

When an animal goes from healthy to sick

37
Q

How is incidence measured?

A
  • can be measures as a rate with time component in the denominator
  • risk (fraction from 0-1)
38
Q

What does incidence represent?

A

force of disease

39
Q

Prevalence at a given moment in time, generally the default understanding of prevalence

A

point prevalence

40
Q

number of cases identified over a period of time (1 year = annual prevalence):

A

period prevalence

41
Q

Prevalence can change based on:

A

the time that we choose

42
Q

Why is the other name for “prevalence”, a cross sectional study?

A

measure can be thought of as a “cross section” of a population

43
Q

Diseases with long duration can have high prevalence if:

A

they are not fatal

44
Q

Incidence can change dramatically, but why may prevalence not change?

A

if disease has long duration

45
Q

Diseases that have very short durations, or are highly fatal, will have:

A

prevalence near 0

46
Q

What does prevalence convey?

A

the relative need for follow-up care for those affected with a specific disease

47
Q

Useful when assessing primary control measures:

A

indicence

48
Q

Useful to assess the amount of effort needed delivering secondary and tertiary control:

A

prevalence

49
Q

Incidence or Prevalence: Which is more useful in evaluating biosecurity/infection control?

A

incidence

50
Q
  • Have time in the denominator
  • Apply to a group
  • Are scientifically precise
A

rates (incidence density)

51
Q
  • expressed as a proportion
  • applies to a group or individal
  • commonly used, may not account for withdrawals
A

cumulative incidence (risk)

52
Q

Weighted averages of the strata specific rates and strata specific populations

A

crude risks (be they death or other)

53
Q

Important strata to consider in epidemiology:

A

age, breed, sex, production cycle

54
Q

List the steps of the infectious disease events:

A
  1. encounter
  2. entry
  3. spread
  4. multiplication
  5. damage
  6. outcome (restart)
55
Q

the ease with which a disease agent in spread within a population

A

communicability

56
Q

Transmission requires:

A

a susceptible host, an agent, and the “right” environment to establish an effective contact

57
Q

Effective contact is:

A
  • contact between infected and susceptible animals

- contact the results in transmission of disease agent

58
Q

Predicts the number of new cases in the next incubation period interval:

A

reed frost model

59
Q

While a predominately conceptual model, is it very helpful with envisioning the primary elements in an infectious disease outbreak as well as a good estimate in endemic diseases:

A

Reed Frost Model

60
Q

Cases in the time t+1, where 1 represents an interval of time equal to the incubation period of the agent (reed frost)

A

C(t+1)

61
Q

Number of susceptible at time t (reed frost)

A

St

62
Q

the probability of no contact (reed frost)

A

q

63
Q

Cases at time t

A

Ct

64
Q

Each individual in the reed frost model is in one of three categories:

A

S, I, R

65
Q

Average number of secondary cases that develop from one primary case during its entire communicable period in a population of susceptible hosts

A

R0 (R naught)

66
Q

R0 =

A

(# of contacts per unit time) X (probability of transmission per contact) X (duration of infectiousness)

67
Q

If R0 is > 1:

A

the infection is maintained

68
Q

If R0 is < 1:

A

the infection cannot be maintained

69
Q

The ability to protect susceptible individuals within a group due to the high proportion of immune individuals in the same population

A

herd immunity

70
Q

Reduces the number of susceptible (St) and alters the probability of transmission per contact/effective contact:

A

resistance

71
Q

an increased or unexpected occurrence of cases

A

epidemic

72
Q

a normal or expected number of cases in time and space

A

endemic

73
Q

epidemic over a large area - country or worldwide

A

pandemic

74
Q

new cases, force of disease, probability of becoming a case

A

incidence

75
Q

cases at a point in time, “commonness” of disease, probability of being a case

A

Prevalence

76
Q

Visual display of disease occurrence in time

A

epidemic curve

77
Q

What are the two basic types of epidemics:

A

common source, propagated

78
Q

Common-Source Epidemic:

A

results from exposure to a common source (such as contaminated food or water)

79
Q

Point (or point-source) epidemic:

A

exposure is sudden and brief (potato salad at a picnic)

80
Q

Extended Common Source Epidemic:

A

exposure period is prolonged

81
Q

The initial slope of the epidemic curve is stepper when the animal density is:

A

higher

82
Q

The initial slope of the epidemic curve is steeper when the infectious period is:

A

longer

83
Q

What does the slope of the curve suggest?

A

efficiency of transmission within the population

84
Q

What’s an example of a short term trend?

A

epidemic

85
Q

What’s an example of a cyclical trend?

A
  • seasonal

- periodic changes in susceptible host population

Epidemiology (3 decks)

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