LECTURES 1-8

Question 1

What is Epidemiology (definition)?*

Answer 1

THE STUDY OF THE DISTRIBUTION AND DETERMINANTS OF HEALTH RELATED STATES AND EVENTS IN POPULATIONS AND THE APPLICATION OF THIS STUDY TO THE CONTROL OF HEALTH PROBLEMS

> Health related states = diseases, BMI, blood pressure, etc.

Question 2

What is an “Epidemic”?

Answer 2

THE OCCURRENCE IN A COMMUNITY OR REGION
OF CASES OF AN ILLNESS, SPECIFIC HEALTH-RELATED BEHAVIOUR, OR OTHER HEALTH-RELATED EVENTS
CLEARLY IN EXCESS OF NORMAL EXPECTANCY.

> > occurrence of disease in excess of normal expectancy

Question 3

DESCRIPTIVE EPIDEMIOLOGY

Answer 3

Examining the distribution of a disease in a population, and OBSERVING the basic features of its distribution in terms of time, place, and person.

> Typical study design: community health survey

Question 4

ANALYTIC EPIDEMIOLOGY

Answer 4

Testing a SPECIFIC HYPOTHESIS about the relationship of a disease to a putative cause by conducting an epidemiological study that relates the exposure of interest to the disease of interest.

> Typical study designs: cohort, case-control

Question 5

Ratio

Answer 5

Relationship between two numbers

– Example: males/females

Question 6

Proportion

Answer 6

A ratio where the numerator is included in the denominator

– Example: males/total births

Question 7

Rate

Answer 7

A proportion with the specification of time

– Example: (deaths in 1999/population in 1999) x 1,000

Question 8

What is “Endemic”?

Answer 8

constant presence of a disease, e.g. malaria is endemic in sub-Saharan Africa

Question 9

e. Purposes of epidemiology

Answer 9

i. Identify causes and risk factors for disease.
ii. Determine the extent of disease in the community.
iii. Study natural history and prognosis of disease.
iv. Evaluate preventive and therapeutic measures
v. Provide foundation for public policy

Question 10

1. Crude death rate

Answer 10

= deaths from all causes in a time period

a. A proportion
b. Like Cumulative Incidence but population = entire defined population, since everyone’s at risk

Question 11

2. Cause-specific mortality rate

Answer 11

deaths from one specific cause in a time period

Question 12

3. Case-fatality rate

Answer 12

= cumulative incidence of death among those who develop an illness
a. CF = (# ppl who die from specific disease) / (# ppl with the disease during that time period)

Question 13

1. Point prevalence

Answer 13

proportion of the population affected by the disease at a given point in time

a. (# cases of disease in popul’n at a specified time)/(# ppl in popul’n at that specified time)
b. Denominator includes people living with disease

Question 14

2. Period prevalence

Answer 14

proportion of the population affected by the disease during a certain time period

a. Numerator: prevalent cases + incident cases
b. (# cases of disease in popul’n during a specific time period)/(# ppl in popul’n during that time period)

Question 15

1. Cumulative incidence

Answer 15

a. (# of new cases during a time period)/(total popul’n at risk, i.e. w/o disease)
b. Proportion – ranges from 0 to 1 or 0% to 100%
c. Measures avg risk of developing outcome over certain period of time

Question 16

2. Incidence rate/Incidence Density

Answer 16

a. (# of new cases during a time period)/(people-time at risk)
b. Person-time at risk = amount of time a population is at risk for developing a disease
c. Ranges from 0 to ∞

Question 17

i. Outbreak

Answer 17

occurrence of disease that is greater than would be expected at a >particular timeparticular place

Question 18

ii. Index case

Answer 18

the first recognized case in a defined outbreak or epidemic (“patient zero”)

Question 19

iii. Primary case

Answer 19

the (true) first case in a defined outbreak or epidemic (often only determined in retrospect)

Question 20

iii. Secondary case

Answer 20

cases who were infected by the index case (i.e., same disease/strain)

Question 21

c. Attack rate

Answer 21

cumulative incidence of infection in a group of exposed susceptible hosts

i. Attack rate = (# persons infected)/(total # of exposed susceptible persons during outbreak)
1. Susceptible bc some ppl have immunizations and are actually not susceptible to a disease

Question 22

d. Basic reproductive number (Ro, “R-not”)

Answer 22

the avg # of secondary cases one case generates, e.g. if one person infects 3 others, Ro = 3

i. Infection will spread in the population if Ro > 1
ii. Infection will reach an endemic phase if Ro = 1
iii. Infection will die out in the population if Ro

Question 23

e. Herd immunity

Answer 23

Proportion of popul’n that would need to be vaccinated to prevent an outbreak

Once a certain threshold has been reached, herd immunity will result in the elimination of the disease from the population
ii. If V = herd immunity threshold, then:

V = 1 – (1/Ro)

Question 24

1. Sentinel events

Answer 24

occurrences of diseases that are harbingers of broader public health problems, e.g. suicide, wrong site surgery, fall, medication error

Question 25

Sentinel Surveillance

Answer 25

reporting of sentinel events by select institutions or individuals