What does infectiousness refer to?

The ability to transmit infection

Who is the new host in disease transmission?

A recipient of the disease agent

Incidence density rate (ID) measures the rate of:

Newly developed cases in a specified population

What represents a rate in the given examples?

Speed at which students become zombies

What is a limitation when studying open populations?

Cannot estimate a true (unbiased) risk

What methods assume normal data in statistics?

ANOVA, t-tests, linear regression

What is required for transmission via contact?

Adequate contact per transmission route

What does the basic reproductive number (R0) represent?

The expected number of secondary cases from one infection

What does "uncertainty" describe for individuals?

Inability to predict individual outcomes

Why might theoretical transmission modes lack empirical evidence?

They have not been studied under practical conditions

Can animals be infectious for different transmission modes?

Yes, they could be infectious for one mode but not another

What influences resistance factors in hosts?

Genetic susceptibility and immunity

What is the formula for the mortality rate?

(Number of deaths) ÷ (Total population-time at risk)

What is required for an individual to be included in incidence measurements?

Must have previously been outcome-free

How is a disease agent transmitted?

Through direct or indirect contact

What factors drive disease transmission?

Infectious individuals and immunity levels

What defines a disease agent?

The pathogen causing the disease

What can cause differences in crude rates between regions?

Differences in age structures or risk factors

What is required for a valid proportion?

Numerator is included in denominator

What is the relationship between odds and probabilities?

Odds can be close to probabilities

What model assumes random chance is not part of the causal pathway to disease?

Deterministic model of causation

Why is adequate contact a theoretical concept?

It requires precise experimental conditions

Which of the following will increase the prevalence of insulin-dependent diabetes?

Increasing survival time with the disease

What does the formula p = K / (N - 1) represent in disease transmission?

Probability of adequate contact

Can animals be infectious for different transmission modes?

Yes, they could be infectious for one mode but not another

How is uncertainty defined in this context?

Unpredictability; indeterminacy; indefiniteness

Which is an example of a proportion?

Percent of class that is a zombie

Another possible denominator for cumulative incidence is:

number of people who spent time in population and were at risk for disease

How is airborne transmission different from direct contact?

It can occur over greater distances

What is the primary goal of epidemiology?

Produce valid population estimates

Cumulative incidence is calculated as:

(# of new cases) / (Total population at risk)

Calc CI use total number of individuals who spent time in the population & were at risk for disease would:

Include individuals who may not have been present for the full duration

What does the denominator of the mortality rate represent?

Total population-time at risk during the study

Why are specific rates more accurate for comparisons between regions?

They account for age and other risk factors

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Epidemiology: Data Types II & Disease Outbreak, Measures of Disease I

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Questions 200

Answers

1
Decreasing recovery rate (e.g., withholding therapy) would:
Increase incidence
Decrease prevalence
Increase prevalence
Have no effect on disease presence
2
In an open population, it is not possible to calculate risk without:
Using time-at-risk data
Including withdrawals
Accounting for disease resolution
Error
3
What does infectiousness refer to?
The presence of clinical signs
The ability to transmit infection
The severity of disease symptoms
4
What commonly occurs in open populations?
No population changes
Censoring
Complete closure
5
Who is the new host in disease transmission?
An immune individual
A recipient of the disease agent
The transmitting vector
6
Incidence density rate (ID) measures the rate of:
Total cases in a fixed population
Disease recurrence in a population
Newly developed cases in a specified population
Disease resolution over time
7
What represents a rate in the given examples?
Proportion infected by lecture end
Speed at which students become zombies
Percent of zombie epidemiologists
8
What is a limitation when studying open populations?
Lack of disease data
Cannot estimate a true (unbiased) risk
Difficulty tracking births
9
What methods assume normal data in statistics?
ANOVA, t-tests, linear regression
Non-parametric tests
Regression with large samples
10
Time component must be specified for which of the following calculations?
Cumulative incidence
Prevalence
Recovery rate
Survival analysis
11
What is required for transmission via contact?
All contacts are sufficient
Adequate contact per transmission route
Contact must include symptoms
12
What does the basic reproductive number (R0) represent?
The total number of infected individuals
The expected number of secondary cases from one infection
The number of infections in an immune population
13
What does "uncertainty" describe for individuals?
Inability to predict individual outcomes
Exact probability of disease
Rate of disease transmission
14
Why might theoretical transmission modes lack empirical evidence?
They are less common than other modes
They have not been studied under practical conditions
They do not involve susceptible hosts
15
Can animals be infectious for different transmission modes?
Only during clinical disease
No, they are always infectious by all modes
Yes, they could be infectious for one mode but not another
16
What influences resistance factors in hosts?
Only the environment
Pathogen mutation
Genetic susceptibility and immunity
17
How is incidence density rate similar to "mph"?
Both measure total distance over time
Both remain constant
Both are instantaneous rates
18
What is the formula for the mortality rate?
(Number of deaths) ÷ (Total population-time at risk)
(Deaths) × (Population at risk)
(Total cases) ÷ (Population size)
19
What is required for an individual to be included in incidence measurements?
Must have previously been outcome-free
Must have been vaccinated
Must already have the disease
20
What must be specified when calculating rates?
Time units
Disease severity
Population size
21
How is a disease agent transmitted?
Only via air
Through direct or indirect contact
By shedding alone
22
What factors drive disease transmission?
Genetic mutations and host behavior
Infectious individuals and immunity levels
Only the presence of infected hosts
23
What defines a disease agent?
A genetic mutation
The pathogen causing the disease
A protective substance
24
What can cause differences in crude rates between regions?
Variations in population density
Differences in age structures or risk factors
Similar age structures
25
What is required for a valid proportion?
Numerator is included in denominator
Numerator always > denominator
All data points are continuous
26
What is the relationship between odds and probabilities?
Odds and probabilities are the same
Odds can be close to probabilities
Probabilities always exceed odds
27
What model assumes random chance is not part of the causal pathway to disease?
Deterministic model of causation
Probabilistic model of risk
Stochastic model of causation
28
What does an R0 value of 1 indicate?
Disease is increasing in the population
Disease will not spread in the population
Disease is at an endemic state
29
Why is adequate contact a theoretical concept?
It requires precise experimental conditions
It does not involve host factors
It's only relevant for viruses
30
The most commonly cited denominator in cumulative incidence calculation is:
The number of individuals who recovered
The total population at the end of the study
The number of withdrawals during the study
The initial population size
31
Which of the following will increase the prevalence of insulin-dependent diabetes?
Decreasing incidence of the disease
Increasing survival time with the disease
Increasing recovery rate
Decreasing survival time with the disease
32
What does the formula p = K / (N - 1) represent in disease transmission?
Probability of disease persistence
Probability of adequate contact
Pathogen mutation rate
33
Can animals be infectious for different transmission modes?
Only during clinical disease
No, they are always infectious by all modes
Yes, they could be infectious for one mode but not another
34
What does an R0 value of 1 indicate?
Disease will not spread in the population
Disease is increasing in the population
Disease is at an endemic state
35
How is uncertainty defined in this context?
Unpredictability; indeterminacy; indefiniteness
Probability of outcomes in a population
Predictability and determination
36
Which is an example of a proportion?
Speed at which students become zombies
Percent of class that is a zombie
Number of zombies per hour
37
What do some sources incorrectly refer to this calculation as?
A prevalence rate
A cumulative incidence (CI)
A proportional mortality rate
38
Another possible denominator for cumulative incidence is:
The total population at the end of the study
The number of people who were affected by the disease
The initial population size
number of people who spent time in population and were at risk for disease
39
How is airborne transmission different from direct contact?
It can occur over greater distances
It only happens via vectors
It requires close physical proximity
40
What drives disease translocation?
Immune suppression
Factors enhancing transmission
Lack of vaccination
41
If time-at-risk information is available for all individuals, it may be better to calculate incidence as:
A prevalence
A rate
A proportion
A cumulative incidence
42
What is true about the shape of a normal histogram?
Multiple modes
Skewed distribution
Bell-shaped with one mode
43
What increases the likelihood of disease transmission?
Presence of infectious individuals
Both A and B
Level of population immunity
44
What is the range of incidence density rates?
0 to 100
0 to infinity
1 to 10
45
What does the "distance traveled" represent in this analogy?
New cases of disease
Total cases of disease
Risk of disease
46
What is the primary goal of epidemiology?
Diagnose individual patients
Produce valid population estimates
Identify rare genetic mutations
47
Cumulative incidence is calculated as:
(# of cases during a period) / (Total population during the period)
(# of new cases) / (Total population at risk)
(# of old cases) / (Total population at risk)
Total cases/Population at risk
48
What is important to specify when calculating an average rate?
The age of the population
The geographic location
The time period of evaluation
49
Calc CI use total number of individuals who spent time in the population & were at risk for disease would:
Include individuals who may not have been present for the full duration
Exclude sick individuals from the calculation
Ignore withdrawals and additions
Only consider new cases
50
What does the denominator of the mortality rate represent?
Average population size
Total time elapsed in the study
Total population-time at risk during the study
51
Why are specific rates more accurate for comparisons between regions?
They reflect total population
They only measure mortality
They account for age and other risk factors
52
The numerator in cumulative incidence (CI) calculations is:
The total population at risk
The total duration of disease development
The number of recovered cases
The number of new cases of disease
53
How can an epidemic be prevented based on R0?
The immune proportion must exceed (1 - 1/R0)
Immunity must be less than (1/R0)
Disease transmission must be less than 1
54
Which method of transmission involves vectors or fomites?
Indirect contact
Direct contact
Venereal disease
55
Epidemiologists are most interested in incidence because it measures:
The current presence of a disease in a population
The rate at which new disease cases develop
The duration of disease in affected individuals
The number of recoveries during a time period
56
What does population immunity influence?
Risk of disease spread
Severity of individual symptoms
Probability of disease translocation
57
What is considered adequate contact for disease transmission?
Contact causing transmission between infectious and susceptible hosts
Contact between immune hosts
Any contact, regardless of immunity
58
Which of the following is an example of a closed population?
Closed dairy herds
Urban wildlife populations
Free-ranging animal groups
59
What method evaluates normality assumptions?
Plotting histograms and descriptive stats
Statistical hypothesis testing
Using mean and variance only
60
What does the numerator of the mortality rate represent?
Number of deaths during the study period
Total population size
Number of new cases of disease
61
How is the probability of adequate contact between hosts calculated?
By the equation 1 - (1 - p)^Ct
By multiplying p with N
By the number of susceptible individuals
62
What does the denominator of the mortality rate represent?
Time elapsed since the disease outbreak
Population time at risk of dying
Total population size
63
An example of cumulative incidence could be:
The recovery rate of students who fall asleep
The number of new cases of falling asleep during lecture #1
The total number of cases of falling asleep during the semester
The rate of disease recurrence
64
Epidemiology typically seeks to identify factors associated with:
Recovery rate
Disease treatment options
Disease prevalence
Disease development
65
In acute diseases, prevalence might be low even when incidence is high because:
The disease is rare
The disease resolves quickly
Recovery rates are high
The disease develops slowly
66
How can incidence be measured?
As a percentage or total cases
As a prevalence or an average
As a proportion or a rate
67
What is a characteristic of a closed population?
Members join through migration
Members stay unless disease or death occurs
Censoring occurs frequently
68
What is the key feature of cause-specific rates?
Compare death rates across different age groups.
Measures disease by a specific cause
Measure the total death rate in a population.
69
What is another method to estimate population time at risk?
Adjusting the initial population of risk
Ignoring additions or withdrawals
Using the total population size
70
What happens when R0 is greater than 1?
The disease will be eradicated
Disease transmission will cease
The number of cases will increase, leading to an epidemic
71
What is the dimension of the incidence density rate?
Cases per unit time
Percentage of population
Cases per square mile
72
How is the probability of adequate contact between hosts calculated?
By the number of susceptible individuals
By the equation 1 - (1 - p)^Ct
By multiplying p with N
73
In an open population, calculating risk is challenging due to:
Lack of a clearly defined numerator
The changing population size over time
The absence of time-at-risk data
Frequent disease resolution
74
What is the source of a disease agent?
Vector
Infected host
Environment
75
How do pathogens enter via the respiratory tract?
Fecal-oral transmission
Aerosols (
Skin contact
76
How does an agent escape from the infected host?
Via vectors
By mutation
Through shedding
77
In an open population, calculating risk is not possible without:
Accounting for withdrawals
Continuous assessment of the population
Error
Using cumulative incidence
78
What unit is analogous to "time" in incidence density rates?
Hours
Population time at risk
Total population size
79
Which of the following is true for the age-specific mortality rate?
It restricts both the numerator and denominator to a specific age group
It includes all age groups in the numerator
It measures the risk of death for all age groups combined
80
How do pathogens enter through the skin?
Droplet aerosols
Injections, bites, insects
Fecal-oral route
81
How is a proportion defined in epidemiology?
A / (a + b)
A / (time at risk of becoming A)
A / B
82
What are we primarily interested in when studying disease development?
Random associations
Risk factors for recovery
Factors associated with disease development
83
What term should not be used to describe uncertainty in this class?
Determinism
Probability
Risk
84
When calculating CI in an open population, why is the initial population size typically used in the denominator?
It minimizes the effect of disease resolution
It accounts for individuals who survive through the study
It excludes individuals who leave the study
It ensures an accurate risk measurement for all participants
85
In chronic diseases, the presence of disease could be due to:
Acute disease progression
Rapid disease resolution
Decreased incidence over time
Disease development or survival with the disease
86
What are mechanical or biological vectors in disease transmission?
Infected hosts without clinical symptoms
Pathogens carried by contaminated objects
Organisms that transmit diseases to hosts
87
How is incidence defined?
Total cases in a population
Newly developed cases over time
Cases present at a single point in time
88
Which type of transmission involves contaminated feed or water?
Airborne transmission
Indirect contact
Direct contact
89
What is considered adequate contact for disease transmission?
Contact between immune hosts
Contact causing transmission between infectious and susceptible hosts
Any contact, regardless of immunity
90
How should epidemiological estimates be evaluated?
Through statistical precision
Using anecdotal evidence
By comparing clinical case studies
91
What is incidence?
Newly developed cases in a population during a period
Total cases of a disease at a specific time
Total population at risk of disease
92
What defines direct contact in disease transmission?
Physical proximity, often via respiratory or venereal routes
Airborne transmission over distance
Exposure to contaminated surfaces
93
What is the common transmission route for digestive tract infections?
Aerosols
Skin bites
Fecal-oral transmission
94
Are all infected animals infectious?
No, not all infected animals are infectious
Only if they show clinical signs
Yes, always
95
What is necessary for valid risk application to populations?
Risk corresponds to populations
Risk applied to individuals without error
Risk applies only to isolated individuals
96
The choice of denominator in cumulative incidence is often limited by:
The time spent by each individual in the population
The number of withdrawals during the study
The data available for analysis
The number of new cases observed
97
When measuring cumulative incidence of falling asleep in lecture #1, the time component is:
The total population at the end of the semester
The duration of disease development
The number of students attending the lecture
The total length of the lecture
98
Why might prevalence not be helpful in acute diseases?
Due to the rapid resolution of disease
Because incidence is low
Due to the slow progression from disease-free to diseased
Because disease duration is long
99
Which type of transmission involves contaminated feed or water?
Direct contact
Indirect contact
Airborne transmission
100
What should you multiply population numbers by to estimate population time?
Mortality rate during the study
Length of the observation period
Total number of new cases
101
Which factor increases the prevalence of a disease?
Increased recovery rate
Increased incidence or longer duration
Decreased survival time
Decreased incidence or recovery rate
102
What is a common approximation method for calculating time at risk in an open population?
Using the total number of cases
Time taken to develop the disease
The population size at the beginning of the study
Population at the mid-point of the evaluation period
103
When calculating cumulative incidence (CI) for an open population, it is common convention to use:
The initial population size as the denominator
Only those individuals who remain at risk
The total population at the end of the study
Half of the withdrawn individuals
104
What defines direct contact in disease transmission?
Exposure to contaminated surfaces
Physical proximity, often via respiratory or venereal routes
Airborne transmission over distance
105
What defines risk in epidemiology?
Deterministic model predicting outcomes
Number of outcomes over time
Percentage of animals affected
106
Why are odds considered over probabilities in epidemiology?
Easier to compute
Odds are more accurate
Used in specific study designs
107
What does the formula p = K / (N - 1) represent in disease transmission?
Pathogen mutation rate
Probability of disease persistence
Probability of adequate contact
108
Incidence density rate is useful when:
The disease is acute with a short duration
The population is fixed during the period of study
The population at risk changes over time
There is no disease resolution
109
What do specific rates measure?
Frequency of disease for specific sub-populations
Only the death rate in a population
Total number of cases in all populations
110
When individual-level data is not available for rate calculations, it is best to refer to the measures as:
Incidences
Exact rates
Prevalence
Proportions or approximate rates
111
Cumulative incidence (CI) can be calculated in several ways, but the numerator:
Varies depending on the study
Always remains the same
Is based on the recovery rate
Depends on the time period
112
How is airborne transmission different from direct contact?
It only happens via vectors
It requires close physical proximity
It can occur over greater distances
113
How are additions to the population accounted for?
Add all additions to the population
Ignore additions entirely
Add ½ of the additions, assuming random entry
114
Which factor most influences indirect transmission?
Immune response
Intermediate entities
Pathogen shedding rate
115
Which of the following statements about cumulative incidence is true?
The denominator is always the same
The numerator changes based on the study method
Cumulative incidence is unaffected by time component
The numerator is always the number of new cases
116
When you have time-at-risk data for all individuals, why might it be better to calculate incidence as a rate?
It avoids the need to define a numerator
It accounts for the population at risk over time
It excludes withdrawals
It is easier to calculate than cumulative incidence
117
What defines "odds" in epidemiology?
Prob of occurrence : Prob of non-occurrence
Events : Outcomes
Proportion of events : Total events
118
Which factor directly impacts the measurement of prevalence?
Recovery rate
Disease development rate
Disease duration
Incidence of new cases
119
What determines the choice of "population time"?
Disease and study context
Population size
The total cases observed
120
What does a proportion represent in epidemiology?
Rate of occurrence over time
Speed of outcome development
Risk or probability
121
What is the incidence density rate analogous to?
The fuel efficiency of a car
The distance a car travels
The speed of a car
122
What is required to measure incidence?
Population with existing outcomes
Population with random changes
Population previously outcome-free
123
How can an epidemic be prevented based on R0?
Disease transmission must be less than 1
Immunity must be less than (1/R0)
The immune proportion must exceed (1 - 1/R0)
124
What does the incidence density (ID) rate measure?
Speed of disease occurrence in a population
Prevalence of existing cases
Total number of cases over time
125
An alternative definition of the denominator for cumulative incidence might include:
Half of the new cases added to the initial population
Subtracting half of sick and withdrawals, adding half of the additions
Only the individuals who were diagnosed
Only the population that survived through the study
126
How can epidemiological knowledge improve health?
By replacing clinical medicine
By disease prevention and prediction
By ignoring underlying biology
127
When calculating incidence, it is important to:
Use only the total population size
Define both the numerator and denominator clearly
Always subtract withdrawals from the denominator
Include only individuals who developed the disease
128
What is R0 proportional to?
The rate of adequate contact and duration of infectiousness
The number of susceptible individuals
The number of infected individuals only
129
Incidence can be measured as:
A rate or a prevalence
A recovery rate or rate of new cases
A proportion or a rate
A proportion or survival time
130
Why might theoretical transmission modes lack empirical evidence?
They are less common than other modes
They have not been studied under practical conditions
They do not involve susceptible hosts
131
The confusion in calculating incidence arises due to:
Time periods being inconsistent
Differences in disease recovery rates
Different ways of calculating the numerator
Variability in population at risk
132
What does prevalence measure?
Disease presence at a specific time or period
Disease development during a period of time
Risk of disease in healthy populations
133
What is the incidence density rate of death called?
Mortality rate
Survival rate
Prevalence rate
134
What must an animal be to transmit infection?
Showing severe symptoms
Infected with the pathogen
A carrier of disease
135
What describes a new host in disease transmission?
Intermediate carrier
Agent recipient
Agent transmitter
136
Prevalence is defined as:
The incidence of a disease over a year
Total number of cases in a population at a specific time
The number of recoveries in a population
Total number of new cases in a population
137
What is required to calculate rates like incidence density rate?
Total number of cases observed
Average population size
Total population time at risk
138
Which method of transmission involves vectors or fomites?
Venereal disease
Direct contact
Indirect contact
139
What affects a new host's susceptibility?
Vector proximity
Disease prevalence
Immune status
140
What is an example of a vector in indirect transmission?
Mosquito
Air droplet
Surface
141
What is the formula for the incidence density rate?
(New cases) × (Risk population)
(Total cases) ÷ (Population size)
(Number of new cases) ÷ (Total population time at risk)
142
What does Ct represent in the equation for disease transmission?
The number of contacts between susceptible and infectious hosts
The total number of infected individuals
The level of immunity in the population
143
How does transmission occur via fomites?
Contaminated objects
Airborne particles
Direct host-to-host contact
144
What are mechanical or biological vectors in disease transmission?
Pathogens carried by contaminated objects
Organisms that transmit diseases to hosts
Infected hosts without clinical symptoms
145
How are disease-affected animals handled in this calculation?
Add disease-affected animals to the population
Subtract all disease-affected animals
Subtract ½ of the disease-affected animals
146
Prevalence refers to the:
Duration of time a disease lasts
Number of new cases during a time period
Rate of disease development
Presence of disease at a given time or period
147
How are withdrawals from the population accounted for?
Ignore withdrawals
Subtract all withdrawals
Subtract ½ of the withdrawals
148
Which route involves conjunctiva or oral exposure?
Respiratory tract
Skin
Mucous membranes
149
What is direct contact in disease transmission?
Through contaminated objects
From the environment to a host
Host to host transmission
150
Which diseases are typically transmitted via the urogenital route?
Insect-borne diseases
Respiratory infections
Venereal diseases
151
Which of the following is a type of specific rate?
Mortality rate
Cause-specific rate
Crude rate
152
What is a crude rate?
Rate for specific groups
Rate based on total population and cases
Rate limited to a specific cause
153
What defines a closed population?
Members leave only through disease or death
Members can freely enter or exit
Members can leave for any reason
154
What does the cause-specific mortality rate measure?
The mortality rate in a specific age group
The overall mortality rate for a region
The risk of death from a specific cause
155
What factors drive disease transmission?
Only the presence of infected hosts
Genetic mutations and host behavior
Infectious individuals and immunity levels
156
When calculating cumulative incidence (CI) for an open population, the denominator is typically:
The average population during the evaluation period
The initial population size
The total population at the end of the study
The number of new cases only
157
What happens when R0 is greater than 1?
The number of cases will increase, leading to an epidemic
The disease will be eradicated
Disease transmission will cease
158
What defines vertical transmission?
Aerosol transmission
Placenta to offspring transfer
Fecal-oral transmission
159
For both cumulative incidence and incidence density rate, what must be specified?
The disease resolution time
The time component of the study
The total population size
The duration of disease symptoms
160
In epidemiology, which measure is often used to study factors associated with disease development?
Survival time
Recovery rate
Incidence
Prevalence
161
Incidence density rate (ID) differs from cumulative incidence in that ID considers:
A fixed population
The time population is at risk
Disease duration over time
The total number of new cases in a period
162
Decreasing recovery rate in a disease would:
Have no effect on prevalence
Increase prevalence
Increase incidence
Decrease prevalence
163
The primary focus of epidemiology is often on:
Disease duration
The total number of disease cases at a specific time
Decreasing disease incidence
Factors that influence disease development
164
Why might summing each individual’s time contribution be impractical?
Data on cases is incomplete
Time periods are too short
Large populations make it difficult
165
Why is adequate contact a theoretical concept?
It requires precise experimental conditions
It's only relevant for viruses
It does not involve host factors
166
Can an infectious animal lack clinical signs of disease?
Yes, they can be carriers
Only during acute stages
No, clinical signs are necessary
167
What is a method to estimate population time?
Use only the starting population size
Count every individual's time contribution
Use the population midway through the study period
168
What influences resistance factors in hosts?
Pathogen mutation
Only the environment
Genetic susceptibility and immunity
169
What does understanding underlying biology help develop?
Public health policies
Specific tests and therapies
Randomized predictions
170
Why are all rates considered approximations in epidemiology?
Population size remains constant throughout the study
We never have continuous assessment of the population
We can accurately assess time at risk for all individuals
Disease resolution is always tracked precisely
171
How can individuals join a closed population?
By recovering from disease
By immigration
Through birth
172
What is an example of indirect transmission via vectors?
Transmission through contaminated objects or surfaces
Airborne particles over distance
Direct physical touch
173
What does Ct represent in the equation for disease transmission?
The level of immunity in the population
The number of contacts between susceptible and infectious hosts
The total number of infected individuals
174
What does incidence measure?
Disease development over time
Disease presence at a point in time
Total number of diseased individuals
175
When is the term uncertainty appropriately used?
When random chance affects disease causation
When discussing disease in populations
When we don't know if an individual will develop an outcome
176
How can incidence be measured?
As a proportion or a rate
As a cumulative total
As a ratio only
177
What does the basic reproductive number (R0) represent?
The number of infections in an immune population
The total number of infected individuals
The expected number of secondary cases from one infection
178
What does estimating measures of association help infer?
Causality
Disease prevalence
Random chance
179
What does incidence density rate describe?
The rate of newly developed cases in a specified population
The proportion of existing cases over time
The total population exposed to a disease
180
An approximation method for calculating time at risk includes:
Including only the individuals who survive through the study
Using only the initial population for both numerator and denominator
Subt half of sick individuals and withdrawals, add half of the additions
Excluding individuals who developed the disease
181
What is the correct way to express potential disease development?
As uncertainty
As a risk value
As a proportion of cases
182
Which measure is more important for understanding causal associations?
Both are equally important
Incidence
Prevalence
183
How does distance affect transmission risk?
1.5 m can prevent some transmissions
Distance has no impact
Only matters for skin contact
184
What facilitates indirect contact transmission?
Vectors or fomites
Direct shedding of agents
Host immunity
185
How can you estimate population time if starting and ending population data are available?
Average beginning and ending population sizes
Use the largest population size observed
Use only the ending population size
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Which is an example of an open population?
Human populations
All-in all-out operations
Closed dairy herds
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What is R0 proportional to?
The number of susceptible individuals
The rate of adequate contact and duration of infectiousness
The number of infected individuals only
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The incidence density rate (ID) is calculated as:
(# of new cases) / (Total population at risk)
(# of new cases) / (Total population at time of risk)
(# of old cases) / (Total population at risk)
(# of new cases) / (Total population during a time period)
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What does incidence specifically measure?
Risk of recovery
Total disease prevalence
New cases over a time period
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For chronic diseases, prevalence is often more useful than incidence because:
The disease develops quickly
The time of disease development is well known
Incidence is more difficult to measure
The flow to disease is slow and presence can be long-term
191
Cumulative incidence (CI) is the:
Rate at which a disease resolves
Number of total cases in a population over time
Proportion of newly developed cases in a fixed population
Rate of recurrence of the disease
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Which of the following measures the development of disease during a specified time period?
Prevalence
Recovery rate
Incidence
Duration of illness
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Incidence refers to the:
Amount of newly developed cases
Total number of cases in a population
Duration of disease presence
Rate of disease recovery
194
What does a mortality rate measure?
The age-specific rate of death
The frequency of disease in a population
The number of deaths in a population
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Why is the incidence density rate considered a dynamic measure?
It only applies to fixed populations
It remains constant in all populations
It changes over time, like car speeds
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What determines sufficient contact for transmission?
The immunity of the contact
Distance from infectious host
The route of transmission
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What defines an open population?
No movement in or out of the population
Only birth allows new members to join
Movement into and out of the population is possible
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What does the numerator of the mortality rate represent?
The number of deaths
The number of new cases
The population size
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What is a major use of epidemiology?
Estimating measures of association
Treating individual diseases directly
Conducting laboratory experiments
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What does the cause and age-specific mortality rate measure?
The overall risk of death across all age groups
Mortality due to a specific cause in the entire population
The risk of death from a specific cause in a specific age group

Epidemiology: Data Types II & Disease Outbreak, Measures of Disease I Flashcards | StudBud