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
What is the equation for incidence rate?
IR = (# new cases over a pd of time)/ (length of time at risk of developing disease)
26
When counting animal-time (time at risk), only count time of:
non-diseased animals
27
Count time for animals until:
- animal gets disease - death from another cause - removed from herd - study terminates - intervention to render it non-susceptible
28
Proportion of non-disease individuals at the beginning of a period of study that become disease during the period:
simple cumulative incidence
29
means they can get the condition:
"at risk"
30
What's the equation for cumulative incidence?
CI = (# of new cases over a period of time)/(number of healthy animals at beginning)
31
A cumulative incidence rate for an outbreak:
attack rate
32
When is it appropriate to measure attack rate?
when the exposure occurs in a very short and defined period of time
33
Attack rate =
(# of new cases)/(number of individuals exposed at the START)
34
Why is IR used less often than CI?
harder to interpret
35
IR is applicable to a group, while CI is applicable to:
a group or an individual
36
What is incidence?
When an animal goes from healthy to sick
37
How is incidence measured?
- can be measures as a rate with time component in the denominator - risk (fraction from 0-1)
38
What does incidence represent?
force of disease
39
Prevalence at a given moment in time, generally the default understanding of prevalence
point prevalence
40
number of cases identified over a period of time (1 year = annual prevalence):
period prevalence
41
Prevalence can change based on:
the time that we choose
42
Why is the other name for "prevalence", a cross sectional study?
measure can be thought of as a "cross section" of a population
43
Diseases with long duration can have high prevalence if:
they are not fatal
44
Incidence can change dramatically, but why may prevalence not change?
if disease has long duration
45
Diseases that have very short durations, or are highly fatal, will have:
prevalence near 0
46
What does prevalence convey?
the relative need for follow-up care for those affected with a specific disease
47
Useful when assessing primary control measures:
indicence
48
Useful to assess the amount of effort needed delivering secondary and tertiary control:
prevalence
49
Incidence or Prevalence: Which is more useful in evaluating biosecurity/infection control?
incidence
50
- Have time in the denominator - Apply to a group - Are scientifically precise
rates (incidence density)
51
- expressed as a proportion - applies to a group or individal - commonly used, may not account for withdrawals
cumulative incidence (risk)
52
Weighted averages of the strata specific rates and strata specific populations
crude risks (be they death or other)
53
Important strata to consider in epidemiology:
age, breed, sex, production cycle
54
List the steps of the infectious disease events:
1. encounter 2. entry 3. spread 4. multiplication 5. damage 6. outcome (restart)
55
the ease with which a disease agent in spread within a population
communicability
56
Transmission requires:
a susceptible host, an agent, and the "right" environment to establish an effective contact
57
Effective contact is:
- contact between infected and susceptible animals | - contact the results in transmission of disease agent
58
Predicts the number of new cases in the next incubation period interval:
reed frost model
59
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:
Reed Frost Model
60
Cases in the time t+1, where 1 represents an interval of time equal to the incubation period of the agent (reed frost)
C(t+1)
61
Number of susceptible at time t (reed frost)
St
62
the probability of no contact (reed frost)
q
63
Cases at time t
Ct
64
Each individual in the reed frost model is in one of three categories:
S, I, R
65
Average number of secondary cases that develop from one primary case during its entire communicable period in a population of susceptible hosts
R0 (R naught)
66
R0 =
(# of contacts per unit time) X (probability of transmission per contact) X (duration of infectiousness)
67
If R0 is > 1:
the infection is maintained
68
If R0 is < 1:
the infection cannot be maintained
69
The ability to protect susceptible individuals within a group due to the high proportion of immune individuals in the same population
herd immunity
70
Reduces the number of susceptible (St) and alters the probability of transmission per contact/effective contact:
resistance
71
an increased or unexpected occurrence of cases
epidemic
72
a normal or expected number of cases in time and space
endemic
73
epidemic over a large area - country or worldwide
pandemic
74
new cases, force of disease, probability of becoming a case
incidence
75
cases at a point in time, "commonness" of disease, probability of being a case
Prevalence
76
Visual display of disease occurrence in time
epidemic curve
77
What are the two basic types of epidemics:
common source, propagated
78
Common-Source Epidemic:
results from exposure to a common source (such as contaminated food or water)
79
Point (or point-source) epidemic:
exposure is sudden and brief (potato salad at a picnic)
80
Extended Common Source Epidemic:
exposure period is prolonged
81
The initial slope of the epidemic curve is stepper when the animal density is:
higher
82
The initial slope of the epidemic curve is steeper when the infectious period is:
longer
83
What does the slope of the curve suggest?
efficiency of transmission within the population
84
What's an example of a short term trend?
epidemic
85
What's an example of a cyclical trend?
- seasonal | - periodic changes in susceptible host population