Principles of CDC and Outbreak Management

Question 1

Full steps for outbreak recognition & management

Answer 1

1. verify and validate source
2. Laboratory definition
3. Initial information: who are they, work, family, location, symptoms
4. gather info to create risk assessment and decide whether high risk or low risk - consider:
   a) severity
   b) number of cases
   c) how infectious/how fast spread
   d) is it happening in a risk setting e.g. school,
5. Risk assessment should decide whether need to Get a control team together (lab, surveillance, communications, school representative, infection control, local authority, minute taker)
6. Devise a case definition and search for further cases
7. Act, notify proper authority, institute disease prevention and control measures
8. Monitor outbreak
9. Establish a working case hypothesis (possible causes of outbreak)
10. further information gathering and data analysis to test case hypothesis
11. debriefing, feedback, report writing at end of outbreak.
    All needs to happen within 24-48 hours.

Question 2

What is forward contact tracing

Answer 2

Focus on who the case has been in contact with that they may have passed it to – doesn’t identify the source

Question 3

Forward and Backward Contact Tracing

Answer 3

To try to identify the source & many more cases

Much more effectively identifies chains of transmission

Question 4

Why don’t always do forward and backward contact tracing?

Answer 4

Don’t have time and resources

Question 5

Public Health Countermeasures to Outbreaks

Answer 5

Hygiene
Social/physical distancing
Isolation
PPE
Treatment as prevention (to prevent transmission)
Chemoprophylaxis - about preventing transmission - you don’t know if the person you are treating has the infection
Vaccination

Question 6

4 overall steps in outbreak management

Answer 6

1. Identify the problem - find out you have a problem
2. Understand the problem - characterise and describe
3. Assess risk
4. Respond to threat - put measures in place to control outbreak and prevent more cases

Question 7

Formal (passive) Surveillance pros and cons

Answer 7

Pros:
- provides baseline
- useful for time-trend analysis
- lab reports are accurate and timely
Cons:
- limited range of diseases
- often delayed
- frequently absent
- may only show tip of the iceberg

Question 8

Examples of formal sources of surveillance

Answer 8

surveillance data
reports from labs
disease notifications from HCPs

Question 9

Examples of informal sources of surveillance

Answer 9

key informants in affected community e.g. head teacher at affected school

Question 10

Enhanced Surveillance pros and cons

Answer 10

Pros:
- much more accurate picture
- good clinical data –> good epidemiology
Cons:
- labour intensive
- not useful for bigger picture
- needs commitment

Question 11

What information is needed to understand the problem
(Clinical, microbiology, epidemiology)

Answer 11

Clinical:
- what is the presentation suggestive of
- is this a clinical or microbiological diagnosis
- how severe is it
Microbiology:
- do we have an organism
Epidemiology:
- do we have an outbreak?
- how many cases
- are they associated
- is there evidence of a point source
- is there evidence of person to person spread

Question 12

When to do a cohort vs case control study (in epidemiology)

Answer 12

If have a full cohort - do cohort; if you don’t know the whole cohort, do a case control

Question 13

What to look at in a risk assessment

Answer 13

Certainty - are you sure of cause and source
Spread - how many are infected, how wide is spread
Severity - how severe are the outcomes? How bad can it get
Sensitivity to PH Measures - how easy is it to control?
“Anxiety” - how much public, political and media concern is there

Question 14

Who should be in an incident management team? (IMT aka OCT (outbreak control team)

Answer 14

Depends on incident
- health protection specialists
- infectious disease physicians
- microbiologist
- environmental health officers
- laboratory staff e.g. food scientists
- health authority/commissioners
- regional and national experts as required
- who is involved in similar work e.g. WHO, UNICEF, NGOs etc

Question 15

How to do case finding?

Answer 15

• active surveillance
• alert local clinicians and other relevant stakeholders e.g. environmental health
• encourage sampling to identify cases
• alert regional contacts
• alert national and international contacts as required

Question 16

Further investigations in outbreak management

Answer 16

• identify the at risk group e.g. family, school class, club, neighbourhood
• identify a common factor in the cases e.g. food item, place of work, residence, behaviour,
• generate or review hypothesis
• consider a case control or cohort study to test hypothesis

Question 17

What case definition would you use for persons with possible novel coronavirus infections who have recently travelled to/from the Middle East?

Answer 17

• Persons with a fever >38C (or history of a fever) AND severe respiratory symptoms (SoB, cough)
  AND
• with a history of recent travel to or from countries in the Middle East where there have been reports of novel coronavirus infections (e.g. Saudi Arabia, Jordan)

Question 18

What should a working hypothesis determine?

Answer 18

Causative agent of disease
Likely source
who is likely to be at risk
What exposure predisposes to disease
What risk factors predispose to disease
How to prevent more cases

Question 19

Identifying the source

Answer 19

There is often insufficient evidence - lab confirmation often needed
Need to sample widely to identify source
By the time microbiological sampling is carried out, the source of the outbreak may no longer be around –> therefore it is also useful to carry out direct observation e.g. observing food preparation and hygiene practices in a restaurant

Question 20

Source-receptor pathway for infection control

Answer 20

• Kill or inactivate infectious agent at source (Abx for index cases, environmental measures (decontamination, sterilisation, heat treatment)
• Interrupt pathway of transmission (isolation of vulnerable and affected individuals, environmental hygiene measures, personal hygiene, PPE)
• Protect the receptor/host (isolation of vulnerable persons, immunisation, chemoprophylaxis)

Question 21

For diarrhoeal disease outbreak, what indicators would you use to monitor the situation

Answer 21

• number of persons with symptoms (cases)
• number of persons hospitalised
• number of persons who die as a result of the disease (case fatality)

Question 22

What considerations would determine frequency of monitoring and approach for monitoring (routine or active surveillance)

Answer 22

• risk posed by the infectious agent (spread/severity of disease)
• reliability of routine reporting systems
• completeness of routine reporting systems (what proportion of cases are detected and reported)
• timeliness of routine reporting systems (are there delays, is reporting too infrequent etc.)
• ## practical considerations (availability of resources to implement and sustain heightened surveillance)

Question 23

What to consider in a risk assessment

Answer 23

Severity
Number of cases
How infectious/how fast spread
Is it happening in a risk setting e.g. a school