Lecture 17- Outbreak Investigation Methods

Question 1

What are the 10 steps in outbreak investigations

Answer 1

1.prepare for field work
2. Determine the existence of an outbreak
3. Confirm the diagnosis
4. Identify and count cases
5. Tabulate data and perform descriptive epidemiology
6. Consider implementing control measures
7. Develop hypotheses (analytic epidemiology)
8. Plan for additional studies
9. Implement and evaluate control measures
10. Communicate findings

Question 2

Prepare for field work what are the investigation and administration needs as well as logistics and dynamics

Answer 2

Investigation needs: supplies, lab, expertise

Administrative needs: team leader, procedures

Logistics and dynamics: where to go/who to meet, what is your rople

Question 3

Determine the existence of an outbreak

Answer 3

Is it an outbreak, epidemic or cluster

Real vs. artifcat

Question 4

What is a cluster

Answer 4

Grouping of cases in a. Given place or time

Question 5

What is the difference between real vs artifact

Answer 5

Changes in surveillance methodology can result in appearance of an outbreak when there isn’t one

Question 6

Confirm the diagnosis

Answer 6

Ensure proper diagnosis- do all individuals have same disease, lab error?

Examine initial case patients, review medical records

Question 7

Identify and count cases

Answer 7

Who is a case, index case, case definition

Question 8

What is an index case

Answer 8

Refers to the first case in a disease outbreak

Question 9

What is a working case definition

Answer 9

Criteria: 4 components
Clinical presentation
Who
Where
When

Question 10

What are the categories of certainty

Answer 10

Confirmed, probable, possible

Question 11

What are common symptoms of an outbreak

Answer 11

Fever, nausea, diarrhea, vomiting, headache, rashes, stomach pain

Question 12

Tabulate data and perform descriptive epidemiology

Answer 12

Organize and visualize data, identify patterns, identify possible causative agents based on symptom onset and incubation period, identify possible exposure sources based on symptom onset

Perform descriptive epidemiology

Question 13

Descriptive epidemiology for time, place and person

Answer 13

Time: epidemic curve
Place: orient top areas of concern-spot map
Person: describe case group

Question 14

What is line listing and what is collected

Answer 14

Table or database of case information

Information collected: demographic, clinical, epidemiological

Question 15

Epidemic curve

Answer 15

Graphical depiction of the number of cases of illness by the date of illness onset

Question 16

What are two types of epi curves

Answer 16

Common source
Propagated source

Question 17

What is a common source epidemic curve

Answer 17

All cases are exposed to agent from the same source

Point source, continuous source, intermittent sourc

Question 18

What is a propagated source epidemic curve

Answer 18

Secondary cases exposed to primary cases

Question 19

What information does epidemic curve provide

Answer 19

Patterns of spread, outliers, magnitude, time trend, exposure and/or period of incubation

Different shapes of graph reveal the type of outbreak

Question 20

Consider implementing control measures

Answer 20

Target to:
Eliminate the source, interrupt transmission, reduce susceptibility

Question 21

Develop and test hypothesis

Answer 21

Review descriptive epidemiology, explain outliers, generate hypothesis, analytic epidemiology, compare results

Question 22

What are the two case design options for analytic epidemiology

Answer 22

Cohort study and case control study

Question 23

Odds ratio

Answer 23

Measures strength of association between exposures and outcomes in case control studies

OR=ad/bc

Question 24

Odds ratio +1

Answer 24

No difference between expose and outcome

Question 25

Odds ratio <1

Answer 25

Protective effect- the outcome is less likely in the exposed group

Question 26

Odds ratio >1

Answer 26

Outcome is more likely in exposed groups the higher the number the stronger the association

Question 27

Attack rate formula

Answer 27

(# new cases/ # in population rise) x 10^n

Question 28

What is the food specific attack rate formula

Answer 28

(# ill persons who ate food/ total # who ate the food) x100

Question 29

Plan for additional astudies

Answer 29

Improve quality of numerator and denominator data

Question 30

What are two additional study types

Answer 30

Environmental and laboratory

Question 31

Implement and evaluate control measures

Answer 31

Evaluate impact of control measures taken at step 6, modify as needed, active surveillance to monitor for new cases

Question 32

Communicate findings

Answer 32

Document, justify recommendations