1. Detection of unusual events
Integrated Disease Surveillance Programme (IDSP) district surveillance officers (DSO) course

2. Preliminary questions to the group
Have you ever detected an outbreak?
If yes, what difficulties did you face?
What would you like to learn about early outbreak detection?
Warm up questions for five minutes. 2

3. Outline of the session From denial to vigilance Early warning signals
Triggers in the Indian Integrated Disease Surveillance Programme (IDSP)
Outline. 3

4. Cases of cholera by date of onset, South 24 Parganas, West Bengal, India, May 2006
Here?
When to investigate? 30 25 20
Here?
Number of cases
Never? 15
Here?
Important slide.
This is an outbreak. It could be investigated either at the beginning, when the number of cases is rinsing, at the peak or never.
Ideally it should be at the beginning. But in your district, it might be never.
So what you want is to progressively improve so that it gets better.
But it might not go from no investigations to early investigations overnight. 10 5 24 25 26 4 27 28 29 30 1 2 3 4 5
April
May

5. When are outbreaks investigated in your district?
When the first cases occur?
An indication of vigilance
When there is a large cluster?
Shows reactivity
When most cases have occurred?
The team only acts under pressure
Never
Denotes denial
This provides additional explanations on the first slide.
The four bullets parallel the four arrows on the graph in the previous slide, providing more detail about what the timing of the investigation wil denote.
Fighting denial 5

6. Reasons why public health professionals might deny outbreaks
No skills to investigate
Additional work
No intervention to offer
Press pressure
Fears of sanctions
Often there are many reasons not to investigate.
Here are some.
Can you think of others?
Fighting denial 6

7. Turn challenges into opportunity
Investigation methods can be learned
Investigations become easier with practice
Data guides effective prevention measures
Good investigations impress the press
Leaders appreciate signs that the situation is under control (e.g., ongoing investigation)
But in fact, each of these “Good reasons not to investigate” can be turned into opportunities.
See how each of these bullets on this slide parallel the bullets on the previous slide.
Fighting denial 7

8. Improving the outbreak detection situation
The number one obstacle to fight is denial
Once there is a willingness to address outbreaks, technical methods may be used to ensure the earliest possible detection
The system will not go from denial to early detection overnight
But every small progress matters
It is never too late to investigate an outbreak
You will still learn, but it is more difficult
More on the same theme: You won’t change the situation overnight.
Fighting denial 8

9. Two ways to detect unusual events
Event-based surveillance
Reports of events
Case-based surveillance
Routine surveillance data analysis
There are two ways to detect unusual events.
Event-based surveillance is about event. It works like the reporter who will capture a story heard.
For example: There was an outbreak of gastro-enteritis following a major wedding in a village.
Case-based surveillance is about following trends based on regular data analysis to detect unusual rises.
For example: There is three times as much measles this month than during the same month last year.
Early warning 9

10. Components of early warning surveillance
Case-based surveillance
Event-based surveillance
Data
Reports
Analyze
Filter
Signal
Validate
Verify
Alert
Response
Assess
Whichever system is considered -like on this flowchart- there is a process to transform SIGNALS into ALERTS through either analysis and validation (case based surveillance) or through filtering and verification (event based surveillance).
When an alert is given, it leads to response.
Public health alert
Investigate Control measures
Post-outbreak strengthening
Evaluate
Early warning 10

11. Two ways to detect unusual events
Event based surveillance
Collect reports
(e.g., toll free line, internet search, press scan)
Filter
Identify signals
Verify
Case base surveillance
A development of event based surveillance. It works like journalism when a journalist checks a story.
Early warning 11

12. Early warning signals for event-based surveillance
Clustering of cases or deaths
Single case of disease of epidemic potential
Acute febrile illness of unknown etiology
Two or more linked cases of meningitis, measles
Unusual isolate
Shifting in age distribution of cases
High vector density
Natural disasters
These are the kind of events that can be signals to be filtered and verified.
Early warning 12

13. Sources of information for event-based surveillance
Rumour register in each institution
Standardized format
Investigation for each entry
Tracking system to document follow up
Community informants
Private and public sector
Media
Important source of information, not to neglect
24 x 7 call centre
To gather events you also need a reporting system. It is as for case surveillance.
Early warning 13

14. Two ways to detect unusual events
Event based surveillance
Case base surveillance
Collect data
Analyze data
Detect signals
Validate signals
This is a development of case-based surveillance.
Early warning 14

15. Challenges to surveillance data analysis to detect unusual events
Imperfect data
Changes over time
Multiple sources of information
Problem of quality and completeness
Need an in-depth knowledge of the system
Evaluation
To know what is unusual, you need to know what is usual
It is difficult to do case based surveillance because the system is not perfect.
So you must know your system.
Like if you know your old car, you will know what is really abnormal among the various noises that it makes.
Early warning 15

16. Sources of false alarm Changes in the numerator
Increased awareness about a disease
Appointment of a new surveillance person
Acute reporting of old, chronic, cases
Changes in the denominator
Population movements
Some causes of false alarm.
Early warning 16

17. Triggers in the context of the Indian Integrated Disease Surveillance Programme (IDSP)
Threshold for diseases under surveillance that trigger pre-determined actions at various levels
Based upon the number of cases in weekly report
Trigger levels depend on:
Type of disease
Case fatality (Death / case ratio)
Number of evolving cases
Usual trend in the region
To make the system easier IDSP has a number of triggers.
Triggers 17

18. Levels of response to different triggers
Significance
Levels of response 1
Suspected /limited outbreak
Local response by health worker and medical officer 2
Outbreak
Local and district response by district surveillance officer and rapid response team 3
Confirmed outbreak
Local, district and state 4
Wide spread epidemic
State level response 5
Disaster response
Local, district, state and centre
These triggers work by levels that define their significance and anticipate their level of response.
Triggers 18

19. Malaria triggers Trigger 1 Trigger 2:
Single case of smear positive in an area where malaria was not present for a minimum of three months
Slide positivity rate doubling over last three months
Single death from clinically /microscopically proven malaria
Single falciparum case of indigenous origin in a free region
Trigger 2:
Two fold rise in malaria in the region over last 3 months
More than five cases of falciparum of indigenous origin
Triggers for malaria.
Triggers 19
* State may set their own triggers

20. Cholera triggers Trigger 1 Trigger 2
A single case of cholera / epidemiologically linked cases of diarrhea
A case of severe dehydration / death due to diarrhea in a patient of >5 years of age
Clustering of cases in a particular village / urban ward where more than 10 houses have at least one case of loose stools irrespective of age per 1000 population
Trigger 2
More than 20 cases of diarrhea in a village/geographical area of 1000 population
Triggers for cholera.
Triggers 20

21. Typhoid fever triggers
More than 30 cases in a week from the entire primary health centre area
5 or more cases per week from one sub-centre of 5,000 population
More than 2 cases from a single village/urban ward/1000 population
Clustering of cases of fever
Trigger 2
More than 60 cases from a primary health centre or more than 10 cases from a sub-center
Triggers for typhoid.
Triggers 21

22. Polio trigger
One single case
Triggers for polio.
Triggers 22

23. Plague triggers Trigger 1 Trigger 2 Rat fall
At least 1 probable case of plague in community
Triggers for plague.
Triggers 23

24. Japanese encephalitis triggers
Clustering of two or more similar case from a locality in one week
Trigger 2
More than four cases from a PHC (30,000 population) in one week
Triggers for Japanese encephalitis.
Triggers 24

25. Dengue triggers Trigger 1 Trigger 2
Clustering of two similar case of probable Dengue fever in a village
Single case of Dengue hemorrhagic fever
Trigger 2
More than four cases of Dengue fever in a village with population of about 1000
Triggers for dengue.
Triggers 25

26. Triggers for syndromic surveillance
Fever
More than 2 similar case in the village (1000 Population)
Diarrhea
See cholera
Acute flaccid paralysis
1 case
Jaundice
More than two cases of jaundice in different houses irrespective of age in a village or 1000 population
Triggers for syndromic surveillance.
Triggers 26

27. Basic responses to triggers
There are triggers for each condition under surveillance
Various trigger levels may lead to local or broader response
Tables in the operation manual propose standardized actions to take following various triggers
Investigations are needed in addition to standardized actions
The operation manual defines what to do in view of each trigger.
Triggers 27

28. Progressive response Levels of alert are progressively increasing
Unusual signals require filtering / validation
The best chance of detection is to:
Analyze regularly
Be familiar with the time, place and person characteristics of the diseases in your area
The response may be of increasing magnitude.
Triggers 28

29. Public health events of international concern need to be reported as per new International Health Regulations (IHRs)
Public health events
Sudden serious and unexpected event that require immediate action
Outbreak of epidemic prone diseases
Any other event that may have impact on the health of a community (natural or man-made catastrophes)
International concern
Risk of spread beyond the borders of the affected country (agent/host/environment or capacity to contain the event)
One specific point is the International Health Regulations.
These ask for reporting of public health events of international concern.
Those are defined as on this slide.
Triggers 29

30. Take home messages
Fight denial by showing what can be usefully done about outbreaks
Investigations
Control measures based on evidence
Consider case-based and event-based surveillance
Recognize triggers and respond to them as per guidelines
Take home messages. 30

31. Additional reading Section 4 of IDSP operations manual
Module 8 of training manual
Triggers 31