Lecture 2: Descriptive Epi and Measures of Disease Freq

Question 1

2 aspects of DISTRIBUTION of a disease

Answer 1

Frequencies and Patterns

Question 2

Frequency of disease occurrence considers

Answer 2

Counts in relation to size of a population

Question 3

3 aspects of PATTERNS of disease occurrences

Answer 3

Person, Place, Time

Question 4

Distribution of disease= __ Epidemiology

Answer 4

Descriptive Epi (who, where, when)

Question 5

When to use Descriptive Epidemiology

Answer 5

When occurrence of disease is more frequent than usual or greater compared to other areas.

Question 6

3 types of surveillance systems

Answer 6

Passive, active, syndromic

Question 7

System waits for disease/conditions to come to them

Answer 7

Passive Surveillance System

Question 8

Search through communities for new cases of disease/conditions

Answer 8

Active Surveillance System

Question 9

Focus is looking for signs/symptoms that could lead to disease/conditions

Answer 9

Syndromic Surveillance System

Question 10

subtype of Syndromic Surveillance; looks for signs/symps not just in humans, but also in animals, plants, environment.

Answer 10

Biosurveillance

Question 11

Induction/Incubation period

Answer 11

Time between exposure and onset (disease process starts) of disease

Question 12

Latency period

Answer 12

Time between onset and detection of disease

Question 13

Timeline for Disease

Answer 13

1. Susceptability
2. 5 (Exposure)
3. Subclinical changes (pathologic changes occur)
4. 5 (Onset of symptoms)
5. Clinical Stage (usual time for diagnoses)
6. Recovery, Disability, or Death stage

Question 14

Element that must be defined before ‘Who’

Answer 14

Case Definition

Question 15

Define disease/condition for public health surveillance

Answer 15

Case Definitions

Question 16

Department that makes case definitions (infectious and non)

Answer 16

Council of State and Territorial Epidemiologists (CSTE)

Question 17

Department that collects specific types of disease from subnational (state, local, etc) health departments in order to monitor, control, prevent disease

Answer 17

National Notifiable Diseases Surveillance System (NNDSS)

Question 18

Confirmed vs Probable case defs

Answer 18

Probable-likely to have condition but key factor for accurate diagnosis has not been met
Confirmed-key factor for diagnosis has been met

Question 19

Newsletter based from NNDSS that reports notifiable diseases at the national level

Answer 19

Morbidity and Mortality Weekly Report (MMWR)

Question 20

Disease occurrence is higher than normal.

Answer 20

Epidemic

Question 21

Localized higher than normal increase in disease occurrence (smaller scale compared to epidemic)

Answer 21

Outbreak (aka cluster)

Question 22

Higher than normal disease occurrence is a norm in a given area.

Answer 22

Endemic

Question 23

Pre-pandemic alert that epidemic should be taken under cautionary measures

Answer 23

Emergency of International Concern

Question 24

Epidemic spread world-wide

Answer 24

Pandemic

Question 25

Graphical study monitoring outbreak/epidemic cases over time and is used to form hypotheses of occurrences; incorps Descriptive Epi (3 W's)

Answer 25

Epidemic Curve

Question 26

3 visual factors an epidemic curve presents

Answer 26

1. Magnitude (number of cases, vertical axis) 2. Timing (occurrences over time; horizontal axis) 3. Pattern (if disease is continuously spreading or not; shape of curve)

Question 27

Index or sentinel case/case zero

Answer 27

First documented person with onset of disease

Question 28

2 aspects of PATTERNS in an epicurve

Answer 28

1. Point source-common, single source that passes the disease continuously or intermittently; not propagated (ex. broadstream pump) 2. Propagated- person-person spread

Question 29

Hypotheses from epicurves include understanding

Answer 29

1. transmission route 2. probably exposure period (graph, begins at point 0) 3. incubation period

Question 30

No sentinel case; continuous over time, not propagated or repeated

Answer 30

common/point source graph with no exposure

Question 31

Yes sentinel case, continuous over time, not propagated or repeated

Answer 31

common/point source graph with index case

Question 32

There is repetition of disease occurrence

Answer 32

Common/point source graph with intermittent outbreak

Question 33

Yes sentinel case, there is propagation of infected infecting others (secondarily) and others infect others (spread)

Answer 33

person-to-person outbreak

Question 34

Maximum incubation period

Answer 34

period between time of exposure and last incident case

Question 35

Average incubation period

Answer 35

Period between exposure and highest peak of a continuous epicurve

Question 36

Minimum incubation period

Answer 36

Period between exposure and first detected incident cases

Question 37

3 numerical measures of disease frequencies

Answer 37

Proportions, Ratios, and Rates

Question 38

Proportion

Answer 38

part over whole; simple percentage; numerator is related to the denominator (ex. same individs in population)

Question 39

Ratio

Answer 39

Division of two unrelated numbers (ex. different individs from a population of interest)

Question 40

Rate

Answer 40

Proportion with time incorporated in the denominator

Question 41

3 key factors when comparing disease freqs BETWEEN groups. If factors 2 and 3 are not the same between groups, what do we do?

Answer 41

1. number of people who are infected (count) 2. size of source pop (those who have disease) OR those at risk (those who do not have disease) 3. Time-length that the population was followed We need standardize values (have a common denom)

Question 42

New cases of a disease

Answer 42

Incidence

Question 43

Existing plus new cases

Answer 43

Prevalence

Question 44

______ and ______ are proportions; they factor in the 'at risk' OR 'base' populations into the denominator

Answer 44

Incidence, prevalence

Question 45

How does prevalence decrease?

Answer 45

infected persons have gotten cured or have died

Question 46

How does prevalence increase?

Answer 46

infected persons are being treated, prevent from dying sooner

Question 47

How do you prevent incidence?

Answer 47

Prohibit actively (vaccinations) or are immune

Question 48

Equation for incidence

Answer 48

aka risk/attack rate incidence=new cases/AT RISK population (REMEMBER: in denom, subtract those who already have disease or are immune!)

Question 49

When is the equation for incidence useful?

Answer 49

When numerator and denom are unchanging (non-dynamic)

Question 50

When the incidence/risk/attack rate for a NON-DYNAMIC POPULATION is summed over multiple time periods

Answer 50

Cumulative incidence

Question 51

What to do when we are evaluating a population in which it would be near-impossible to determine who IS and who ISN’T at risk during known time?

Answer 51

Will have to estimate the population.