1. Principles of Outbreak Management

2. Definition of outbreak
Occurrence of more cases of disease than expected in a given area among a specific group of people over a particular period of time or
Two or more linked cases of the same illness

3. Objectives of outbreak investigations
To control continuing outbreaks
To prevent future outbreaks
To provide statutorily mandated services
To strengthen surveillance at local level
To advance knowledge about a disease
To provide training opportunities

4. Specific demands when investigating outbreaks
Unexpected event
Need to act quickly
Need for rapid control
Work carried out in the field
Systematic approach

5. Steps of an outbreak investigation
Confirm outbreak and diagnosis
Case definition and identification
Descriptive data collection and analysis
Develop hypothesis
Analytical studies to test hypotheses
Special studies
Implementation of control measures
Communication, including outbreak report

6. Detection Is this an outbreak? Routine surveillance
Clinical / Laboratory
General public
Media
Detection
Is this an outbreak?
Diagnosis verified ?
clinical + laboratory
Link between cases?
Expected numbers?

7. Sequence of Events in outbreak detection and confirmation (I)
Primary
Case
1st case
at HC
Report
to DMO
Samples
taken
Lab
result
Response
begins
CASES
Opportunity
for control
DAY

8. Sequence of events in outbreak detection and confirmation (II)
Response
begins
PRIM HC
REP
SAMP
RES
Potential
Cases Prevented
CASES
DAY

9. Outbreak confirmed
Immediate control
measures?
Further
investigation?

10. Outbreak confirmed Immediate control measures? Further investigation?
Unknown aetiology
(pathogen/source/transmission)
Cases serious
Cases still occurring
Public pressure
Training opportunity
Scientific interest
Prophylaxis
Exclusion / isolation
Public warning
Hygienic measures
Assistance ?

11. Outbreak Investigation Team?
FIELD
Epidemiologist
Microbiologist
Environmental specialist
Ministry / Government
Press officer
Others
Outbreak Investigation Team?

12. Clinicians Epidemiology Coordination Education Laboratory Authorities
Vector
Reservoir
Dead
Sick
Investigation
Surveillance
Prediction
Exposed
Clinicians
Epidemiology
Coordination
Education
Laboratory
Clinical
Health
personnel
Specimen
transfer
Special
groups
General
population
Diagnostic
Media
Authorities
Decisions
Infrastructure
Regulations
Vaccinations etc

13. Outbreak Investigation Team?
Epidemiologist
Microbiologist
Environmental specialist
Ministry / Government
Press officer
Others
Outbreak Investigation Team?
Assess situation
Examine available information
Preliminary hypothesis ?
Case definition
Case finding
Descriptive epidemiology

14. Case definition
Standard set of criteria for deciding if a person should be classified as suffering from the disease under investigation.
Clinical criteria, restrictions of time, place, person
Simple, practical, objective
Sensitivity versus specificity

15. Case definition: example
Patient older than 5 years with severe dehydration or dying of acute watery diarrhoea in town “x” between 1 June and 20 July 1998

16. Case definition: categorisation
Possible
Patient with severe diarrhoea
Probable
Patient older than 5 years with severe dehydration or dying of acute watery diarrhoea in town “x” between 1 June and 20 July 1998
Confirmed
Isolation of Vibrio cholerae from stool of patient

17. Perform descriptive epidemiology
Clearly identifiable groups
Hospitals
Laboratories
Schools
Workplace, etc
Identify & count cases
Obtain information
Perform descriptive epidemiology

18. Perform descriptive epidemiology
Identify & count cases
Identifying information Demographic information
Clinical details
Risk factors
Obtain information
Perform descriptive epidemiology

19. Perform descriptive epidemiology
Identify & count cases
Obtain information
Orient cases in
- time
- place
- person
Perform descriptive epidemiology

20. Cases Time Person Place Evaluate information Pathogen? Transmission?
Source?

21. Cases of viral meningitis by date of admission (n=416) Cyprus, 5 July - 5 November 5 1996

22. Examples of epidemic curves
Point source
Examples of epidemic curves
Multiple waves -person to person or further outbreak
Continuing common source

23. Admissions per 100,000 population for viral meningitis by age group
Admissions per 100,000 population for viral meningitis by age group. Cyprus, 5 July - 5 November 1996

24. Admissions per 100,000 population for viral meningitis by district; Cyprus, 5 July - 5 November 1996
Nicosia
F. Famagusta
Paphos
Larnaca
1-49
50-99
100 +
No data
Cases per 100,000
Limassol

26. Compare hypotheses with facts
Develop hypotheses
Who is at risk of becoming ill?
What is the disease causing the outbreak?
What is the source and the vehicle?
What is the mode of transmission?
Compare hypotheses with facts

27. Test specific hypotheses Analytical epidemiological studies
Cohort
Case-control

28. Implement control measures May occur at any time during the outbreak!!
Control the source of the pathogen
Interrupt transmission
Modify host response
Prevent recurrence

29. Control the source of pathogen
Remove source of contamination
Remove persons from exposure
Inactivate / neutralise the pathogen
Isolate and/or treat infected persons

30. Interrupt transmission
Interrupt environmental sources
Control vector transmission
Improve personal sanitation

31. Modify host response Immunise susceptibles
Use prophylactic chemotherapy

32. Aetiology Source/Transmission Investigation +++ Control +
unknown
known
Investigation +++
Control +
known
Investigation +
Control +++
Aetiology
Investigation +++
Control +++
Investigation +++
Control +
unknown
Source: Goodman 1990

33. At the end Prepare written report Communicate public health messages
Influence public health policy
Evaluate performance

34. Thank you