Transcript Epidemic Alert System

Outbreak Alert and Response Systems:
a review
February 2004
Ayana Yeneabat, MD, MPH
Epidemiologist, WHO
What is an outbreak?
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A public health emergency!
A political emergency!
An economic emergency!
An unusual event!
An event requiring rapid action!
Surveillance failure!
Control failure!
An opportunity !
Influenza pandemics 20th century
Credit: US National Museum of Health and
Medicine
1918: “Spanish Flu”
1957: “Asian Flu”
20-40 million deaths
1-4 million deaths
A(H1N1)
A(H2N2)
1968: “Hong Kong Flu”
1-4million deaths
A(H3N2)
DF/DHF re-emerging infectious diseases
No report
Total population of the SEA Region = 1.5 billion
Total population at risk
= 1.3 billion (87%)
Source: FAO
Ebola (Viral Haemorrhagic Fever)
in Africa
What is outbreak management?
The process of anticipating, preventing, preparing for,
detecting, responding and controlling disease outbreaks
in order that health and economic impacts are minimised
Surveillance: Information for Action
Components of Effective Outbreak
Management
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Anticipation/Prediction
Preparedness
Early warning/Surveillance
Effective and co-ordinated
response
• Evaluation
Components of Effective Outbreak
Management
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Anticipation/Prediction
Preparedness
Early warning/Surveillance
Effective and co-ordinated
response
• Evaluation
Reported cases of encephalitis in Nepal,
1997-1998: Prediction/trends
350
1997
300
Cases
250
1998
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150
100
50
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Source: EWARS
Week No
Effect of rainfall in producing RVF
Epizootics in Kenya 1950-1982:
Composite rainy days x rainfall surplus
(12 month accumulated figure)
Forecast/Metrological Data
RVF EPIZOOTICS
Davies et al. 1985. Bull. WHO. 63:941-3.
Components of Effective Outbreak
Management
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Anticipation/Prediction
Preparedness
Early warning/Surveillance
Effective and co-ordinated
response
• Evaluation
Epidemic Preparedness and Response
Plan
• What should be done ?
• Who should do it ?
• What resources or supplies will
be required ?
Components of Epidemic Preparedness
1 Established planning and co-ordination
mechanism
2. Agreed priorities
3. Implemented epidemic preparedness plan
(surveillance, response etc)
4. Functional early warning system
5. Capacity for rapid implementation of plans
Components of Effective Outbreak
Management
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Anticipation/Prediction
Preparedness
Early warning/Surveillance
Effective and co-ordinated
response
• Evaluation
What is the Early Warning/surveillance
objective for outbreaks?
• To predict, detect and confirm outbreaks
of public health importance in a timely
fashion and to disseminate that
information to those who need to know
so that effective public heath action can
be taken
What are the components of an
effective early warning system ?
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Small number of priority diseases
Syndromic reporting
Simple case definitions
Processes for dealing with rumours
Rapid case investigation and sampling
Rapid laboratory confirmation
Standard procedures for information sharing
and initiation of response
• Preparedness plans in place
Outbreak Alerts: Thresholds
 Absolute numbers
1 case of AFP or rabies
 Relative values compared to similar period
Need to establish trend
 Absolute rate over a period
Population at risk and index cases (2/100,000)
 Statistical cut-offs
Time series modeling (deviations)
Outbreak Detection and Response:
no functional EWS
First
Case
Detection/
Reporting
Lab
confirmation
Response
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Opportunity
for control
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CASES 50
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Outbreak Detection and Response:
functional EWS
First Case
Detection/
Reporting
Opportunity
for control
Confirmation
Response
DAY
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CASES 50
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How can early warning systems
contribute to outbreak management ?
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Establish the expected
Predict the future
Detect the unexpected (early warning)
Verify/Confirm the existence of an outbreak
Monitor the evolution of an outbreak
Tell you the when outbreak is over
Monitor control programme!
Early warning: tracking of unusual events;
Orissa, India, 2003
Mapping of Reported Disease Outbreaks,
Orissa, MIS/OMDSS, 2003
Components of Effective Outbreak
Management
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Anticipation/Prediction
Preparedness
Early warning/Surveillance
Effective and co-ordinated
response
• Evaluation
Detection
Routine surveillance
Clinical / Laboratory
General public
Media
Confirm outbreak and diagnosis
Diagnosis verified ?
clinical + laboratory
Link between cases?
Expected numbers?
Outbreak confirmed
Immediate control
measures?
Further
investigation?
Control can happen at any time
during the outbreak! But you still
may need to investigate
Point source
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Examples of
epidemic curves
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Continuing common source
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11 13 15 17 19
Multiple waves -person to person
or further outbreak
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Post outbreak Tasks
• Prepare written report
• Communicate public health
messages
• Convince public health policy
• Evaluate performance
PREPAREDNESS
Committee
Priorities
Plan
Co-ordination
Responsibilities
Resources
Supplies
Training
Surveillance
Rapid Response
OUTBREAK CONTROL
Investigate
Detect &
Confirm
Analyse
Respond
Treat
Control
Predict
& Prevent
Evaluate
Attributes: detection, alert, response
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EWARN, Sudan
DEWS, Pakistan
KO-SURV, Kosovo
EWORS, Indonesia
EAST TIMOR
EWARS, Nepal
• Global outbreak alert and response network (GOARN)
• Global Public Health Intervention Network (GPHIN)
• Orissa-MDSS/MIS/Early Warning
• Gujarat/Kachchh District Early Warning System
• NSPCD/IDSP In India: focus on early epidemics
Hallmark: information for prompt action
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Timely Information
Real time transfer of information
Sound Analysis
Instant and meaningful Interpretation
Prompt and effective response
Feedback
Simple and flexible to context
Partnership: Key for EWS