Week 1 - Overview of the Discipline of Epi & Descriptive Epidemiology

Question 1

What is the definition of Epidemiology?

Answer 1

A basic science that studies the determinants and distribution of a disease in a population in order to control a disease and illness and promote health

Question 2

What are the STEPS Epidemiologists take? Data Source Assess Hypothesis Testing Action

Answer 2

Data Source = descriptive Epi. 3Ws Assessment = Inference (possibly stat analysis) Hypothesis Testing = Analytic Epi. (compare groups, rates, etc.) Action = community intervention

Question 3

What are the STEPS Physicians take?

Answer 3

Date Source = history and physical exam Assessment = differential diagnosis Hypothesis testing = lab work, X-rays, etc. Action = diagnose/treatments

Question 4

What are the objectives and activities in Epidemiology? (6)

Answer 4

1. Identify patterns in groups over time. 2. Determine extent of the disease. 3. Identify causes of risk factors 4. Study the diseases natural course 5. Evaluate effectiveness of treatment and preventative measures 6. Develop public health policies in POPULATIONS

Question 5

What are the Epidemiological assumptions? (3)

Answer 5

1. Disease occurrence is not random 2. Systematic investigation of different populations can id associations and causal/preventative factors and changes/adjustments can improve health of that pop. 3. Making comparisons should be done for systematic disease assessments and investigations

Question 6

What are the distribution factors? (2) (Description Epi 3Ws)

Answer 6

1. Frequencies of occurrence - in relation to population size 2. Patterns of occurrence - person, place, time

Question 7

What are the determinants? (4) (Analytic Epi 1W/1H)

Answer 7

Why/How 1. Factors of susceptibility/exposure/risk 2. Etiology/cause of disease 3. Mode(s) of transmission 4. Social/Environmental/Biological elements

Question 8

What are the core functions of Epidemiology? (6)

Answer 8

1. Public health surveillance (passive/active) 2. Field Investigation 3. Analytic studies 4. Evaluation 5. Linkages 6. Policy development

Question 9

What is the purpose of public health surveillance? What are the key skills?

Answer 9

Find ongoing patterns, to develop, and apply investigation, control, and preventative measure. i.e. reportable disease registry (NNDSS/NEDSS), morbidity/mortality/birth registries Skills: data collection instruments, data management, data interpretation, scientific writing and presentation

Question 10

What is the purpose of Analytic studies?

Answer 10

to advance the hypothesis that was generated. Key skills: design, conduct, analysis, interpretation and communication of research study data and findings

Question 11

What is the purpose of Field investigation?

Answer 11

To determine the source of vehicle of disease, learn about its natural history, clinical spectrum; descriptive epi. i.e. ground beef as an E. coli source, eggs as Salmonella source

Question 12

What is the purpose of Linkages?

Answer 12

To collaborate/link with other professionals

Question 13

What is the purpose of policy development?

Answer 13

To provide input, testimony, and recommendations regarding disease control and prevention strategies, reportable disease regulations and health-care policy

Question 14

What is descriptive epidemiology used for?

Answer 14

To know if a site/location is experiencing disease occurrence more frequently than usual. Must first determine the CASE definition (diagnostic criteria)

Question 15

What are surveillance systems used for?

Answer 15

To determine if a disease is occurring and to count the frequency of that disease

Question 16

What are the 2 surveillance systems?

Answer 16

Passive Active Syndromic - patients who have predefined systems/signs that are being reported or evaluated. Biosurveillance

Question 17

What are CASE definitions?

Answer 17

Uniform criteria to define a disease/condition for public health surveillance to classify and count cases consistenly across reporting jurisdictions. Probable vs. Confirmed case definitions

Question 18

Epidemic

Answer 18

Excess of normal expentancy; abnormally high

Question 19

Outbreak/Cluster

Answer 19

Epidemic that’s limited to a localized increase, more concentrated area

Question 20

Endemic

Answer 20

Constant presence within a given area/population in excess of normal levels elsewhere i.e. HIV in Africa

• There’s NO end!

Question 21

Pandemic

Answer 21

Worldwide epidemic occurrence i.e. Swine Flu

Question 22

What does the epidemic curve help us locate? (2)

What can they help us form hypothesis on? (3)

Answer 22

1. Pattern of spread - (shape) common or point source (continous & intermittent)
2. Magnitude of impact - sentinel case/peak/outliers, time trends (rate of occurrence), start/stop/duration

Hypothesis: routes of transmission, probably exposure period, incubation period

Question 23

What is a common point source (common source outbreak)

Answer 23

An outbreak that comes from one source; common

Question 24

What is the National Notifiable Diseases Surveillance System (NNDSS)?

Answer 24

A public health surveillance system that’s classified and counted by cases consistently; via a set of uniform criteria that’s used to define a disease/condition for this surveillance.

Question 25

Syndromic Surveillance

Answer 25

A type of surveillance system where patients who have predefined signs/symptoms that are being reported or evaluated.

Question 26

Sentinel/Index Case

Answer 26

peak/outliers/isolated case

Question 27

How does a graph look that has an intermittent outbreak that is repeated?

Answer 27

Question 28

Graphical representations of incubation periods on a graph:

Answer 28

Question 29

What are the 3 basic types of relative measures of dieases frequencies utilized by epis?

Answer 29

1. Ratios - division of 2 unrelated numbers (numerator is not apart of the denominator)
2. Proportions - division of 2 related numbers (num is a subset of the denominator)
3. Rates - division of 2 numbers with time in the denominator

Question 30

Absolute differences

Answer 30

The absolute difference of two real numbers; the absolute value of their difference

Question 31

Case Definitions

Answer 31

Clinical criteria on whether an individual is included as a case in an outbreak investigation

Question 32

Case fatality rate

Answer 32

A measure of the severity of a disease, the proportion of reported cases of a specified condition/disease which are fatal within a specified time (measure of severity within a specified time)

Question 33

Cumulative Incidence

Answer 33

The probability that a particular disease has occurred before a given time

Question 34

Incidence

Answer 34

The occurrence, rate, or frequency of a disease

Question 35

Incidence Rate

Answer 35

The number of new cases per population at risk in a given time period

Question 36

Incidence density

Answer 36

• The number of new cases in a given area expressed at person-time of those AT RISK

When the denominator is the sum of the person-time of the at risk population

Question 37

Period Prevalence

Answer 37

The proportion of a population that has the condition at some time during a given period, includes people who already have the condition at the start of the study period and during that period

Question 38

Prevalence vs. Incidence

Answer 38

Prevalence is widespread; all affected individuals at a particular time.

Incidence is a measurement of the # of newly affected individuals who contract disease during a particular time period

Question 39

Attack Rate/Incidence Proportion

Answer 39

The rate at which a new case occurs within a given time period; the demonimator is the population at risk

Question 40

Crude Morbidity Rate

Answer 40

Disease rate with a given time span

Question 41

Crude Mortality Rate

Answer 41

Death rate within a given time span