Week 8

Question 1

outbreak

Answer 1

An outbreak or epidemic exists when there are more cases than expected of a particular disease among a specific group of people and/or in a given area, over a particular period of time

Question 2

pandemic

Answer 2

world wide epidemic

Question 3

epidemic

Answer 3

more cases than usual

Question 4

outbreak

Answer 4

same as an epidemic; may be smaller number of cases, area or population

Question 5

cluster

Answer 5

group/aggregation of cases usually in one specific location

Question 6

endemic

Answer 6

permanent/regular disease incidence

Question 7

why do outbreaks occur?

Answer 7

New appearance of an infectious agent (Or toxic material) from the environment or from an infected source
Arrival of susceptible people to an environment with an endemic pathogen
Introduction of effective route of transmission from source to susceptible population (e.g. climate change bringing new mosquito species)

Question 8

oubtreak investigation had

Answer 8

primary goals
secondary goals
factors that impact our process and decision making

Question 9

Outbreak investigation- primary goals

Answer 9

Identify pathogen or source
Control
Prevent future outbreaks
All the above in a timely manner

Question 10

Outbreak investigation- secondary goals

Answer 10

Learn more about a disease

Training opportunity

Question 11

Outbreak investigation- factors that impact our process and decision making

Answer 11

Case numbers
Disease severity
Risk to others
public/political/legal concerns

Question 12

Steps of an outbreak investigation

Answer 12

Prepare for field work
Verify the existence of the outbreak
Confirm the diagnosis
Define and identify cases
Describe/orient data (person, place, time)
Develop hypotheses
Evaluate hypotheses
Refine hypothesis/perform additional studies
Implement control and prevention measures
Communicate findings

Question 13

Step 1: prepare for field work

Answer 13

Epidemiological knowledge and homework 
What are the usual risk factors? Previous outbreaks? 
Supplies and equipment 
Competent laboratory 
Portable computer, phone, supplies 
Team composition 
Who should be in team? Who is in charge? 
Statistical advisors, public relations, local information 
Administrative 
Transport and communication 
travel, cash, credit cards 
immunisation, prophylaxis 
Personal

Question 14

Step 2: verify existence of outbreak

Answer 14

Defined as ‘more cases than usual’ 
What is ‘usual’? 
Must have access to baseline data 
Specific to region 
Specific to current time 
Where are the cases? 
Surveillance: monitoring of disease in populations 
passive, active, sentinel (targeted) surveillance 
Sources of information: 
Surveillance records 
local/state health departments 
Other registries (Hospital discharge records, death records, cancer or birth defect registries)
Clinicians 
Labs
Schools

Question 15

Some causes of false alarms

Answer 15

Change in surveillance/policy of reporting
Change in case deifinition
Improved diagnosis (new test, increased GP awareness, new doctor in town)
False positives from errors in diagnostic tests
Increased public awareness (media coverage leading to demand for tests)
Increased reporting (performance incentives)

Question 16

Step 3: confirm diagnosis

Answer 16

Review clinical findings 
Review lab results of cases 
Be as specific as possible about the causative agent
‘outbreak strain’ of bacteria/virus 
May need specialised lab input 
Talk to cases

Question 17

Step 4: define and identify cases

Answer 17

Case definition is important and can change
Sensitive vs specific
Components include:
Clinical features (bloody diarrhoea)
Person- who to include and exclude
Place- place of residence, where they ate
Time period of interest
Lab results
Divide into:
Confirmed- usually lab confirmed
Probable- lab results not available
Possible- often less stringent clinical criteria
Case finding
Use as many sources as you can
Health care facilities and labs
Alert the public and ask cases to identify themselves
Identify people in place of interest at time of potential exposure and directly contact them

Question 18

Barriers to case detection

Answer 18

Lack of public understanding 
Lack of communication with the public 
On existence of outbreak 
On role of imported health care workers 
Community distrust 
Lack of inclusive planning for outbreak resolution

Question 19

Step 5: describe and orient the data

Answer 19

Time: draw an epidemic curve
Number of cases on y axis
Time on x axis
May provide hints about source of outbreak
Place: map the data
Person: explore data according to personal characteristics

Question 20

Steps 6-8: develop/test/refine hypothesis

Answer 20

What is the source of the infection?
Case control or cohort study?
Other investigations?

Question 21

step 9: control and prevention

Answer 21

Once source of outbreak has been identified, aim to break links in chain of infection 
Do as soon as possible 
Examples: 
Remove contaminated food 
Sterilise contaminated water 
Spray mosquitoes/destroy breeding sites 
isolation/treatment of cases 
Immunise contacts/susceptibles 
Prophylactic medication 
Behaviour modification

Question 22

step 10: communicate findings

Answer 22

Must occur throughout outbreak investigation
Investigation team/partners/press/public
Prepare timely reports
Initial oral briefing (at time leaving the field)
Final written report
Publications
Clearly state facts
Beware of legal implications
Aim to improve practice

Question 23

Down stream factors

Answer 23

helping done in the moment
road design, safety enforcement, excessive speed, driver fatigue, alcohol consumption, use of illicit drugs, use of a mobile phone, absence of effective trauma care

Question 24

upstream factors

Answer 24

what is done to prevent happening again
car use as influenced by fossil fuel energy policies, taxation on alcohol, policing traffic laws, resource allocation to hospital trauma units

Question 25

linear regression

Answer 25

outcome variable must be continuous

exposure may be numerical or categorical

Question 26

strong negative

Answer 26

-0.8 - -1

Question 27

moderate negative

Answer 27

-0.5 - -0.8

Question 28

weak negative

Answer 28

0 - -0.5

Question 29

weak positive

Answer 29

0 - 0.5

Question 30

moderate positive

Answer 30

0.5 - 0.8

Question 31

strong positive

Answer 31

0.8 - 1

Question 32

linear regression assumptions

Answer 32

Outcome variable follows normal distribution (evaluated using histogram or box plot)
Relationship between outcome and covariate is linear
Constant variance of outcome across different values of the covariate remains the same across different values of the covariate

Question 33

residual/prediction error

Answer 33

difference between observed and predicted values

Question 34

coefficient of determination

Answer 34

r^2