EPIDEMIOLOGY MIDTERM EXAM
QUESTIONS AND ANSWERS
Vertical transmission - ANSWER--mother to child transmission
Clinical disease - ANSWER--disease characterized by signs and symptoms
4 types of nonclinical disease - ANSWER-1) preclinical disease
2) subclinical disease
3) chronic disease
4) latent disease
Carrier - ANSWER--a person who harbors a specific infectious agent in the absence of
discernible clinical disease and serves as a potential source of infection
Endemic - ANSWER--the habitual presence of a disease in an area
-the usual level of disease in a population
Epidemic - ANSWER--the occurrence of disease in an area that is in excess of the
normal expectancy
Pandemic - ANSWER--a worldwide occurrence of disease beyond the normal
expectancy
-a worldwide epidemic
Epidemic curve - ANSWER--the distribution of the times of onset (appearance of
symptoms) for cases occurring during an outbreak
-tells us about occurrence of an epidemic, time and source of exposure, mode of
transmission, and causative agent
Herd immunity - ANSWER--the resistance of a group to attack by a disease because a
majority of individuals are immune; thus lessening the likelihood that a susceptible
person will come in contact with a patient with the disease
Incubation period - ANSWER--the interval between from receipt of infection (usually
indicated by the time of exposure) to the time of onset of clinical illness
-a basis for determination of quarantine period
Attack rate - ANSWER--the number of people at risk for a disease who develop the
disease compared to the total number of people who are at risk for the disease during
the outbreak period
Attack rate formula - ANSWER--number of people at risk who develop disease/total
number of people at risk
,Secondary attack rate - ANSWER--the attack rate in susceptible people who are
exposed to a primary case
Case definition - ANSWER--criteria that must be met for the patient to qualify as having
the disease
-fundamental to separate those with and without the disease
-helps ensure accuracy of disease frequency estimates
Quarantine - ANSWER--concerns clinically normal people or animals that might have
been exposed to an infectious agent
-reduced contact with healthy population
Isolation - ANSWER--concerns clinically ill (and likely contagious) individuals
-separated from healthy population
Association - ANSWER--the disease (outcome) is more/less common in people
more/less exposed to some agent
Case - ANSWER--a person identified as having a particular disease, health disorder, or
condition under investigation according to a set of criteria
Incidence - ANSWER--the number of new cases of a disease occurring during a
specified period of time in a population at risk for the disease
-how fast are people getting sick?
-measure of disease frequency
Cumulative incidence - ANSWER--incidence calculated when all persons within the
denominator are considered to be at risk for the disease for the same period of time
-people at risk who are observed throughout a defined (same) time period
-use this as long as the population at risk is relatively stable
-measures RISK
Incidence density - ANSWER--the number of new cases per population at risk in a given
time period
-denominator is the sum of person-time of the at risk population
-measures SPEED
Prevalence - ANSWER--how much disease exists/how many people are sick
-measure of disease frequency
-number of cases of a disease present in the population at a specified time/ number of
persons in the population at that specified time
=incidence x duration
Period prevalence - ANSWER--measure of how many people have a certain
disease/health outcome over a specified period of time
, -may be month, year, etc.
Point prevalence - ANSWER--"snapshot" of how many people have a certain
disease/health outcome at a specified point in time
Ratio - ANSWER--expresses a relationship of one element to a different element where
the numerator is not necessarily a subset of the denominator
Mortality - ANSWER--the number of deaths occurring during a period of time within a
specified population
Case fatality rate - ANSWER--the proportion of persons with a disease who died of that
disease within a specific time frame
-an index of severity of disease
Proportionate mortality - ANSWER--proportion of deaths due to specific cause among
all deaths
Measures of natality - ANSWER--birth rate
-fertility rate
-rate of natural increase
Years of Potential Life Lost - ANSWER--YPLL
-measure of burden of disease
-sum of life expectancy-age at death for all subjects
Disability-adjusted life year - ANSWER--DALY
-a measure of overall disease burden, expressed as the number of years lost due to ill-
health, disability or early death
Standardized rates - ANSWER--differences in age structure of populations is the most
common reason for this practice
-accounting for any number of factors that has an impact of mortality and morbidity in
populations
-definition: artificial constructs to allow easy comparison between populations
2 standardization methods - ANSWER-1) Direct
2) Indirect
Stratum-specific rate - ANSWER--specific rates of disease or death derived from the
population(s) you wish to compare
Standard (reference) population - ANSWER--the population distribution or structure of a
reference population
QUESTIONS AND ANSWERS
Vertical transmission - ANSWER--mother to child transmission
Clinical disease - ANSWER--disease characterized by signs and symptoms
4 types of nonclinical disease - ANSWER-1) preclinical disease
2) subclinical disease
3) chronic disease
4) latent disease
Carrier - ANSWER--a person who harbors a specific infectious agent in the absence of
discernible clinical disease and serves as a potential source of infection
Endemic - ANSWER--the habitual presence of a disease in an area
-the usual level of disease in a population
Epidemic - ANSWER--the occurrence of disease in an area that is in excess of the
normal expectancy
Pandemic - ANSWER--a worldwide occurrence of disease beyond the normal
expectancy
-a worldwide epidemic
Epidemic curve - ANSWER--the distribution of the times of onset (appearance of
symptoms) for cases occurring during an outbreak
-tells us about occurrence of an epidemic, time and source of exposure, mode of
transmission, and causative agent
Herd immunity - ANSWER--the resistance of a group to attack by a disease because a
majority of individuals are immune; thus lessening the likelihood that a susceptible
person will come in contact with a patient with the disease
Incubation period - ANSWER--the interval between from receipt of infection (usually
indicated by the time of exposure) to the time of onset of clinical illness
-a basis for determination of quarantine period
Attack rate - ANSWER--the number of people at risk for a disease who develop the
disease compared to the total number of people who are at risk for the disease during
the outbreak period
Attack rate formula - ANSWER--number of people at risk who develop disease/total
number of people at risk
,Secondary attack rate - ANSWER--the attack rate in susceptible people who are
exposed to a primary case
Case definition - ANSWER--criteria that must be met for the patient to qualify as having
the disease
-fundamental to separate those with and without the disease
-helps ensure accuracy of disease frequency estimates
Quarantine - ANSWER--concerns clinically normal people or animals that might have
been exposed to an infectious agent
-reduced contact with healthy population
Isolation - ANSWER--concerns clinically ill (and likely contagious) individuals
-separated from healthy population
Association - ANSWER--the disease (outcome) is more/less common in people
more/less exposed to some agent
Case - ANSWER--a person identified as having a particular disease, health disorder, or
condition under investigation according to a set of criteria
Incidence - ANSWER--the number of new cases of a disease occurring during a
specified period of time in a population at risk for the disease
-how fast are people getting sick?
-measure of disease frequency
Cumulative incidence - ANSWER--incidence calculated when all persons within the
denominator are considered to be at risk for the disease for the same period of time
-people at risk who are observed throughout a defined (same) time period
-use this as long as the population at risk is relatively stable
-measures RISK
Incidence density - ANSWER--the number of new cases per population at risk in a given
time period
-denominator is the sum of person-time of the at risk population
-measures SPEED
Prevalence - ANSWER--how much disease exists/how many people are sick
-measure of disease frequency
-number of cases of a disease present in the population at a specified time/ number of
persons in the population at that specified time
=incidence x duration
Period prevalence - ANSWER--measure of how many people have a certain
disease/health outcome over a specified period of time
, -may be month, year, etc.
Point prevalence - ANSWER--"snapshot" of how many people have a certain
disease/health outcome at a specified point in time
Ratio - ANSWER--expresses a relationship of one element to a different element where
the numerator is not necessarily a subset of the denominator
Mortality - ANSWER--the number of deaths occurring during a period of time within a
specified population
Case fatality rate - ANSWER--the proportion of persons with a disease who died of that
disease within a specific time frame
-an index of severity of disease
Proportionate mortality - ANSWER--proportion of deaths due to specific cause among
all deaths
Measures of natality - ANSWER--birth rate
-fertility rate
-rate of natural increase
Years of Potential Life Lost - ANSWER--YPLL
-measure of burden of disease
-sum of life expectancy-age at death for all subjects
Disability-adjusted life year - ANSWER--DALY
-a measure of overall disease burden, expressed as the number of years lost due to ill-
health, disability or early death
Standardized rates - ANSWER--differences in age structure of populations is the most
common reason for this practice
-accounting for any number of factors that has an impact of mortality and morbidity in
populations
-definition: artificial constructs to allow easy comparison between populations
2 standardization methods - ANSWER-1) Direct
2) Indirect
Stratum-specific rate - ANSWER--specific rates of disease or death derived from the
population(s) you wish to compare
Standard (reference) population - ANSWER--the population distribution or structure of a
reference population
