Lectures 3-7: Descriptive Epidemiology; Measures of Disease Frequency

Question 1

Descriptive Epidemiology

Answer 1

the Person (WHO), Place (WHERE, Time (WHEN) regarding disease occurrence

Question 2

Case definition

Answer 2

a set of uniform criteria used to define a disease/condition for public health surveillance (like diagnostic criteria in a clinical setting)

Question 3

Epidemic

Answer 3

occurrence of disease clearly in excess of normal expectancy

Question 4

Outbreak

Answer 4

an epidemic limited to a localized increase in the occurrence of disease (may be interchanged with “cluster”)

Question 5

Endemic

Answer 5

constant presence of a disease within a given area or population in excess of normal levels in other areas

Question 6

Pandemic

Answer 6

epidemic occurring over a very wide area involving a large number of people - many times multi-region or multi-national

Question 7

Ratios

Answer 7

Division of 2 unrelated numbers (numerator not part of denominator)

Question 8

Proportions

Answer 8

Division of 2 related numbers (numerator is a subset of denominator)

Question 9

Rates

Answer 9

Division of 2 numbers with TIME incorporated into the denominator

Question 10

Absolute difference

Answer 10

Raw subtraction between two variables

ex: # live births - # total deaths in community

Question 11

Adjusted disease/mortality rates

Answer 11

representation of rates of disease or death among total population, generally adjusted to reflect an appropriate population (such as age-adjusted rates)

ex: age-specific mortality rate: # of deaths of specific age group from any cause / 100,000 people per year

Question 12

Attack rate

Answer 12

new disease cases that develop/# healthy population at risk for disease

*We would have to subtract individuals already diseased or vaccinated in this case

Question 13

Case fatality rate

Answer 13

cause specific deaths/# cases disease

Question 14

Cause-specific morbidity rate

Answer 14

diseased by specified cause/total population

Question 15

Cause-specific mortality rate

Answer 15

cause-specific deaths/total population

Question 16

Cause-specific survival rate

Answer 16

specific cases alive/# cases of disease

Question 17

Common source outbreak

Answer 17

outbreak in which a group of people were all exposed to a disease or toxin at the same time

Question 18

Crude morbidity rate

Answer 18

people with disease/total population

Question 19

Crude mortality rate

Answer 19

deaths/total population

Question 20

Cumulative incidence

Answer 20

new cases of disease/# in candidate population over specified period of time

Question 21

Fertility rate

Answer 21

live births/1,000 women of childbearing age

Question 22

Incidence

Answer 22

new cases/# persons at risk for disease

*subtract out those not at risk

Question 23

Incidence density

Answer 23

new cases of disease/total person-time in population at risk for disease

Question 24

Incidence rate

Answer 24

new cases of disease/person time at risk for disease

Question 25

Incubation period

Answer 25

amount of time from exposure to symptom presentation

Question 26

Induction period

Answer 26

time between exposure to risk factor and initiation of disease

Question 27

Infant mortality rate

Answer 27

of deaths in those less than 1 year old/1000 live births

Question 28

Infectivity

Answer 28

individuals infected/# individuals susceptible

Question 29

Latency period

Answer 29

time between biologic onset of disease and disease detection

Question 30

Live birth rate (Natality)

Answer 30

live births/1,000 population

Question 31

Maternal mortality rate

Answer 31

female deaths related to pregnancy/100,000 live births

Question 32

Morbidity

Answer 32

disease, usually as a rate or proportion of those with disease

Question 33

Neonatal mortality rate

Answer 33

deaths in those less than 28 days old/1000 live births

Question 34

Pathogenicity

Answer 34

with clinical diagnosis of disease/infected individuals

Question 35

Period prevalence

Answer 35

prevalence over a given period of time ex: during 2012, over 1 year

Question 36

Person-time

Answer 36

accounts for the amount of time each person was followed during the study ex: 100 person-years = 100 people followed over 1 year, 10 people followed for 10 years each, etc

Question 37

Propagation outbreak

Answer 37

outbreak which spreads from person-person, infects others (present as repeated spikes on epi curve)

Question 38

Point source outbreak

Answer 38

outbreak in which infected persons were exposed to disease in a single event (such as a meal); curve rises rapidly and falls gradually (present as a bell curve-like blob on the epi curve)

Question 39

Postnatal mortality rate

Answer 39

deaths in those older than 28 days, but less than 1 year/1000 live births

Question 40

Prevalence

Answer 40

of existing cases of disease/# at risk or base population

Question 41

Prevalence rate

Answer 41

incorporates time into prevalence

Question 42

Point prevalence

Answer 42

prevalence at a specific point in time ex: prevalence on January 1st

Question 43

Proportional Mortality Rate (PMR)

Answer 43

cause specific deaths/total # deaths in population

Question 44

Relative difference

Answer 44

ratio of 2 measures of disease frequency (divide them)

Question 45

Risk

Answer 45

Same as incidence; # new cases/# population at risk for disease

Question 46

Secondary attack rate

Answer 46

new cases of disease among contacts/# contacts

Question 47

Sentinel/Index case

Answer 47

original/1st case known (stands alone at beginning of epi curve)

Question 48

Survival rate

Answer 48

that survived/# infected

Question 49

Virulence

Answer 49

deaths/# individuals with disease

Question 50

What key factors are needed to compare measures of disease frequency between groups?

Answer 50

1. # of people affected/impacted (frequency) 2. Size of source population or those at risk 3. Length of time population is followed