1. Outbreak investigation, response and control
Integrated Disease Surveillance Programme (IDSP) district surveillance officers (DSO) course

2. Preliminary questions to the group
What is your experience in outbreak investigations?
If yes, what difficulties did you face?
What would you like to learn about outbreak investigations?
The usual warming up questions for a few minutes. 2

3. Outline of the session Outbreaks and epidemics Outbreak detection
Outbreak investigation
Managerial aspects of outbreak investigations
The outline of the session. 3

4. Endemic versus epidemic
Endemicity
Disease occurring in a population regularly at a usual level
Tuberculosis, Malaria
Epidemics
Unusual occurrence of the disease in excess of its normal expectation
In a geographical location
At a given point of time
e.g. Hepatitis E, measles, cholera
The difference between endemic and epidemic.
Self explanatory. 4
Outbreaks

5. Outbreaks versus epidemics
Occurrence of cases of an illness in excess of expected numbers
Scale
Outbreak
Limited to a small area, within one district or few blocks
Epidemic
Covers larger geographic areas
Linked to control measures in district/state
No exact precise threshold: Use a word or the other according to whether you want to generate or deflect attention
Be aware of legal implications of the use of the term “Epidemic” in India (Epidemic disease act, being revised)
The difference between outbreak and epidemic.
The take home message is: There is no formal difference. You are the one who decide how much importance you want to give to the event.
If you are having lots of measles and none wants to help, call it a major epidemic.
If it is a cluster well under controlled that the press is blowing out of proportion, call it a small outbreak. 5
Outbreaks

6. Sources of information to detect outbreaks
Event-based surveillance
Rumour register
To be kept in standardized format in each institution
Rumours need to be investigated
Community informants
Private and public sector
Media
Important source of information, not to neglect
Case-based surveillance
Review of routine surveillance data and triggers
This slide is a booster dose for the lecture on alert. 6
Detection

7. Early warning signals for an outbreak
Clustering of cases or deaths
Increases in cases or deaths
Single case of disease of epidemic potential
Acute febrile illness of an unknown etiology
Two or more linked cases of disease with outbreak potential
(e.g., Measles, Cholera, Dengue, Japanese encephalitis or plague)
Unusual isolate (Cholera O 139)
Shifting in age distribution of cases (Cholera O 139)
High vector density
Natural disasters
The early warning signals for an outbreak.
Provide additional examples. 7
Detection

8. Importance of timely action: The first information report (Form C)
Filled by the reporting unit
Submitted to the District Surveillance Officer as soon as the suspected outbreak is verified
Sent by the fastest route of information available
Telephone
Fax
The First Information Report is a quick document, a sort of post card from the field that says: This is the alert, we are on our way, we will investigate and we will bring more information. 8
Detection

9. The rapid response team
Composition
Epidemiologist, clinician and microbiologist
Entomologist when vector-borne disease
Gathered on ad hoc basis when needed
Role
Confirm and investigate outbreaks
Responsibility
Assist in the investigation and response
Primary responsibility rests with local health staff
Self explanatory. 9
Detection

10. Objectives of an outbreak investigation
Host
Environment
Agent
An outbreak comes from a change in the way the host, the environment and the agent interact: This interaction needs to be understood to propose recommendations
Verify
Recognize the magnitude
Diagnose the agent
Identify the source and mode of transmission
Formulate prevention and control measures
An outbreak comes from a break in the balance between the host, the environment and the agent.
We need to understand this breach of balance to propose effective control measures.
Hence the objectives of the investigations. 10
Investigations

11. The balance between investigation and control while responding to an outbreak
Source / transmission
Known
Unknown
Etiology
Control +++
Investigate +
Control +
Investigate +++
This is an important slide.
There is a balance between investigation and control measures in outbreak response.
Underline the 2 x 2 table matrix that is the way we think in epidemiology ;-) 11
Investigations

12. Steps in outbreak response
Verifying the outbreak
Sending the rapid response team
Monitoring the situation
Declaring the outbreak over
Reviewing the final report
The steps in outbreak response.
Response is a broader term that covers (1) investigations and (2) control measures. 12
Investigations

13. Step 1: Verifying the outbreak
Validate the source of information
Change in the reporting system
Change in the population size
Acute reporting of old, chronic cases
Check with the concerned medical officer:
Abnormal increase in the number of cases
Clustering of cases
Epidemiological link between cases
Triggering event
Deaths
The step 1 of the outbreak investigation.
We need to verify not to fall in the trap of pseudo outbreaks. 13
Investigations

14. Step 2: Sending the rapid response team
Review if the source and mode of transmission are known
If not, constitute team with:
Medical officer
Epidemiologist
Laboratory specialist
Formulation of hypothesis on basis of the description by time, place and person (Descriptive epidemiology)
Does the hypothesis fits the fact
YES: Propose control measures
NO: Conduct analytical studies
Step 2.
The rapid response team is the strong arm of outbreak response. Multi-disciplinary is the key word.
The slide also introduces the key notion of the two levels:
Generating hypotheses on the basis of descriptive information
Testing hypotheses on the basis of analytical methods.
We want people to be proficient at the first and aware of the second. 14
Investigations

15. Investigating an outbreak
A flow chart presentation of the same.
If the descriptive epidemiology suggests you are dealing with a very well known classical scenario, you may not need analytical methods.
But if there is something you do not understand, then you do need them. 15

16. Example: Outbreak of acute hepatitis (E) in Baripada, Orissa, 2003
Identification of a cluster of acute hepatitis cases
Diagnosis: HEV infection
Use time, place and person analysis of surveillance data to suggests hypotheses
The following few slides will go through an example of hypothesis generation and testing.
It is an hepatitis E outbreak in Orissa. 16

17. Strike among municipal
Time: A cluster a month after a strike in the water treatment centre
Cases of acute hepatitis (E) by date of onset, Baripada, January-March 2004
Investigation 45
started
Cases 40
Deaths 35
Strike among municipal
Workers: Water
treatment stopped 30 25
Number of cases and deaths 20
This is the TIME information: What does it suggest?
Give a moment to the participants. Encourage them to follow the (1) describe and (2) analyze/ interpret steps.
Probably a point source outbreak. It leads us to look into what happened one month earlier: There was a strike in the municipal water treatment plant. 15 10 5
3/1/04
1/1/04
1/3/04
1/5/04
1/7/04
1/9/04
1/11/04
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1/25/04
1/27/04
1/29/04
1/31/04
2/2/04
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2/20/04
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2/24/04
2/26/04
2/28/04
3/3/04
3/5/04
3/7/04 17
Investigations

18. Place: Highest rates next to the pump taking water from river bed
Attack rate of acute hepatitis (E) by residence, Baripada, Orissa, India, 2004
Attack rate
Underground water supply
Pump from river bed
/ 1000
/ 1000
/ 1000
20+ / 1000
Chipat river
This is the PLACE information.
Give a moment to the participants. Encourage them to follow the (1) describe and (2) analyze/ interpret steps.
It seems the disease clusters around the one source of water supply that comes directly from the river. 18
Investigations

19. Person: Attack rate compatible with HEV
Attack rate of acute hepatitis (E) by age and sex, Baripada, Orissa, India, 2004
Cases
Population
Attack rate per 1000
Age
0-4 1
1012
0.1
5-9 11
21802 2
10-14 37
74004 5
15-44
416
51358 81
45+ 73
56153 13
Sex
Male
341
102683
3.3
Female
197
101646
1.9
This is the PERSON information.
Give a moment to the participants. Encourage them to follow the (1) describe and (2) analyze/ interpret steps.
The attack rate by age and sex is highly compatible with HEV. 19
Investigations

20. What hypotheses would you generate for the outbreak of acute hepatitis (E) in Baripada, Orissa, 2003?
Time:
It happens a month after a strike in the water treatment plant
Place:
It is clustered around a water source that takes water from the river
Person:
Adults are mostly affected
Here we summarize the time, place and person information to “connect the dots” and come with a picture that generates an hypothesis:
The hypothesis reads as:
The river water may have been supplied untreated in the area of the outbreak because of the strike at the water treatment plant
The river water may have been supplied untreated in the area of the outbreak because of the strike at the water treatment plant 20

21. Descriptive versus analytical investigations
Descriptive investigations
Based upon cases only
Look at time, place and person epidemiology
Raise hypotheses
Analytical investigations
Based upon a study of the cases and non-cases
Compare:
Cases with controls with respect to exposure
Exposed with unexposed with respect to incidence
Test hypotheses
How could we test the hypothesis for the Baripada investigation?
Again we emphasize the difference between the two levels:
Descriptive / hypothesis raising
Analytical / hypothesis testing
We want them to be proficient at the first and aware of the second.
Brainstorm with the participants how to go about the analytical approach. 21
Investigations

22. Requires assistance from qualified field epidemiologist (FETP)
Steps of a full outbreak investigation using analytical epidemiology to identify the source of infection
Determine the existence of an outbreak
Confirm the diagnosis
Define a case
Search for cases
Generate hypotheses using descriptive findings
Test hypotheses based upon an analytical study
Draw conclusions
Compare the hypothesis with established facts
Communicate findings
Execute prevention measures
Requires assistance from qualified field epidemiologist (FETP)
If we go for a fully fledged investigation with analytical methods, we will use the classical 10 steps.
But that is beyond the skills we expect from the participants of the course.
We would need help from a 2-year scholars of a Field Epidemiology Training Programme. 22

23. Consumption of pipeline water among acute hepatitis (E) cases and controls, Baripada, Orissa, India, 2004
Acute hepatitis
Control
Total
Drunk water from river bed pump
493
134
627
Did not drink pump water 45
404
449
538
1076
92% of cases (493/538) drunk water from suspected source versus 25% (134/538) of controls
If we get back to the Baripada HEV example, this is how the analytical epidemiology was approached with a case control study.
See the language in purple at the bottom: The objective is to remain at a broad, conceptual level.
Analytical epidemiology compares cases and non cases or exposed versus unexposed to test the hypothesis generated on the basis of the time, place and person description 23
Investigations

24. 3. Monitoring the situation
Trends in cases and deaths
Implementation of containment measures
Stocks of vaccines and drugs
Logistics
Communication
Vehicles
Community involvement
Media response
Back to our steps in the investigations. Now step 3: Monitoring the situation. 24
Investigations

25. 4. Declaring the outbreak over
Role of the district surveillance officer / Medical health officer
Criteria
No new case during two incubation periods since onset of last case
Implies careful case search to make sure no case are missed
And step 4. 25
Investigations

26. 5. Review of the final report
Sent by medical officer of the primary health centre to the district surveillance officer / medical and health officer within 10 days of the outbreak being declared over
Review by the technical committee
Identification of system failures
Longer term recommendations
… and step 5. 26
Investigations

27. Outbreak preparedness: A summary of preparatory action
Formation of rapid response team
Training of the rapid response team
Regular review of the data
Identification of ‘outbreak seasons’
Identification of ‘outbreak regions’
Provision of necessary drugs and materials
Identification and strengthening appropriate laboratories
Designation of vehicles for outbreak investigation
Establishment of communication channels in working conditions (e.g., Telephone)
But we do not wait for an outbreak to happen.
We want to be prepared.
Here is a list of the actions to undertake to be ready. 27
Management

28. Managerial aspects of outbreak response
Logistics
Human resources
Medicines
Equipment and supplies
Vehicle and mobility
Communication channels
Information, education and communication
Media
Daily update
So far we have gone through the logical, methodological , intellectual aspects of outbreak investigations.
But there is a managerial aspect also. 28
Management

29. Control measures for an outbreak
General measures
Till source and route of transmission identified
Specific measures, based upon the results of the investigation
Agent
Removing the source
Environment
Interrupting transmission
Host
Protection (e.g., immunization)
Case management
The control measures to undertake.
They should be based on the results of the investigations.
If the outbreak says it was the food handler of the village there is no point in chlorinating the well! 29
Management

30. Take home messages Do not ignore or hide outbreaks
Respond to early warning signals
Investigate outbreaks to:
Control the current outbreak
Learn about the disease in the local setting
Outbreaks require an organized, well managed response
The take home messages. 30

31. Additional reading CDC text book on principles of epidemiology
Section 5 of operations manual
Module 8 of training manual
Here are the additional resources you can use. 31
Detection