Definitions

Question 1

The absolute number of animals that have a particular disease…

Answer 1

Count

Question 2

The count of diseased animals are expressed as a fraction of the animals that could be diseased…

Answer 2

proportion

Question 3

The most common proportion is…

Answer 3

prevalence

Question 4

An expression of the change in the count or amount of disease in a defined population per unit of time…

Answer 4

rate

Question 5

Most common rates are…(2)

Answer 5

cumulative incidence and incidence density

Question 6

A fraction in which the numerator is NOT part of the denominator…

Answer 6

ratio

Question 7

The ratio of the number of diseased to the number NOT diseased…

Answer 7

Odds ratio

Question 8

The proportion of the study population that is diseased at any one time…or the measure of the amount of disease in the population at any one time…

Answer 8

prevalence

Question 9

The proportion of the study population that is diseased at a single point in time…or the probability that an individual in the study pop. is diseased at the time of study…

Answer 9

point prevalence

Question 10

How do you calculate point prevalence?

Answer 10

cases of disease present in the pop. at a particular time/ total pop. at that specified time

Question 11

The proportion of the study pop. that is diseased during a specified period of time that measures all the cases of disease in the study pop. over a period of time is…

Answer 11

period prevalence

Question 12

What type of prevalence includes old cases of disease that were present at the beginning of the time period AND new cases of disease that occur over the time period?

Answer 12

period prevalence

Question 13

How do you calculate period prevalence?

Answer 13

cases of disease present in the pop. over a period of time/ total pop. over that period of time

Question 14

What is the number of new cases of disease that occur in the study pop. over time?

Answer 14

Incidence

Question 15

Incidence is used to predict…

Answer 15

case occurrence in a population

Question 16

Incidence only counts…

Answer 16

NEW CASES of disease

Question 17

The proportion of disease-free (susceptible) individuals in a pop. who became diseased during a specified period of time…

Answer 17

cumulative incidence

Question 18

How do you calculate cumulative incidence?

Answer 18

new cases of disease or events during the time period/ total disease free pop. at risk at the beginning of the time period

Question 19

What is often determined by cross-sectional studies and surveys?

Answer 19

Point Prevalence

Question 20

What is cumulative incidence during an epidemic or the probability (risk) of becoming diseased during the course of an epidemic?

Answer 20

Attack Rate

Question 21

How do you calculate attack rate?

Answer 21

new cases of disease during an epidemic/ total pop. at risk or exposed during that epidemic

Question 22

What is an instantaneous rate of occurrence of new cases of disease among non-diseased animals in the population?

Answer 22

Incidence density (incidence rate)

Question 23

How do you calculate incidence density or incidence rate?

Answer 23

new cases of disease during the study/sum of length of time during which each individual in the pop. is at risk

Question 24

How do you report incidence density?

Answer 24

reported as animal-time at risk

Question 25

How do you report period prevalence?

Answer 25

cases/animal/time

Question 26

How do you report cumulative incidence?

Answer 26

cases/animal/time

Question 27

What measures the amount of disease in a population?

Answer 27

prevalence

Question 28

What measures the rate of disease occurrence?

Answer 28

incidence

Question 29

What is the best measure to assess the overall burden of the disorder, including the costs and resources and reflects the overall magnitude of the disease?

Answer 29

prevalence

Question 30

What is the best measure to asses increasing or decreasing trends in disease frequency and is used to asses the risk factors/causes for the disease?

Answer 30

incidence

Question 31

What is defined as the probability of becoming disease?

Answer 31

Disease risk

Question 32

When an individual is not diseased but is capable of becoming diseased, we say these individuals are...

Answer 32

at risk

Question 33

What are factors that increase the probability of becoming diseased?

Answer 33

risk factors

Question 34

What is the incidence of death in a given time period?

Answer 34

Mortality rate

Question 35

How do you calculate Mortality Rates?

Answer 35

#deaths during the time period/ total pop. during the same time

Question 36

What is the mortality rate due to a specific disease or event?

Answer 36

cause-specific mortality rate

Question 37

How do you calculate cause-specific mortality rates?

Answer 37

#deaths from a specific cause or incident/ total pop. during the same time

Question 38

What is defined as the # of cases that are fatal, within a specified time, following disease onset or diagnosis?

Answer 38

Case Fatality Rate

Question 39

How do you calculate case-fatality rate?

Answer 39

#individual cases of disease that die/total #individuals with the disease

Question 40

In enzootic disease, transmission is sustained over time due to...

Answer 40

1. the result of regularly occurring exposures | 2. a continuous supply of susceptible animals

Question 41

What is a concept in nature of a pop.-level phenomenon which accounts for the reduction in transmission of infectious disease?

Answer 41

herd immunity

Question 42

What are the sources of immunity?

Answer 42

innate, passive or acquired

Question 43

Highly infectious diseases require what amount of immunity?

Answer 43

approximately 95% immunity

Question 44

How can you measure herd immunity?

Answer 44

study the prevalence of antibodies in a population

Question 45

What is the number of secondary cases caused by an infected individual in an entirely susceptible population that determines whether a disease can persist and is valuable for assessing management options?

Answer 45

R0

Question 46

What is a measure of the basic reproductive rate, transmissibility, or spreading potential of an infection in a population?

Answer 46

R0

Question 47

How is R0 calculated?

Answer 47

(#contacts per day) X (probability of transmission per contact) X (duration of infectivity)

Question 48

Diseases are controlled when the R0 is...

Question 49

How do you approximate what % of the pop. that needs to be immune to prevent or stop disease transmission by manipulating R0?

Answer 49

Multiply R0 by the proportion of the pop. that is NOT immune --> R0 X (%naive pop.) If this reduces R

Question 50

What is based upon the probability of transmission from a population of infected cases to a population of susceptible animals?

Answer 50

Reed-Frost Model

Question 51

The Reed-Frost Model is an iterative model that provides a "snapshot" in time, allowing predictions of entire epidemic curves and accounts for the effects of immunity by...

Answer 51

removing immune animals from the "S" or susceptible population with each iteration.

Question 52

The Reed-Frost Model is good when dealing with what type of population?

Answer 52

Large, closed populations

Question 53

Goals of epidemiological studies are...

Answer 53

1. describe the disease (descriptive studies) | 2. identify associations (analytical studies)

Question 54

A good study should be...

Answer 54

1. Scientifically sound 2. Valid 3. Precise 4. Efficient

Question 55

Most Epidemiological studies are...observational or experimental?

Answer 55

Observational

Question 56

When researchers do not know the treatment or exposure status of the subjects, this is called...

Answer 56

blinding

Question 57

What type of study is Ecologic Fallacy a disadvantage and what does that mean?

Answer 57

Ecologic Fallacy is found in Ecological (Analytical) studies. Ecologic Fallacy = the relationship in the pop. may not be true at an individual level

Question 58

What is a tool or method for collecting information about individuals in populations? What studies commonly utilize this method?

Answer 58

Surveys | Cross-Sectional Studies commonly utilize surveys.