View
218
Download
4
Category
Tags:
Preview:
Citation preview
Outbreak Alert and Response Systems: a review
February 2004
Ayana Yeneabat, MD, MPHEpidemiologist, WHO
What is an outbreak?
• 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
A(H1N1) A(H2N2) A(H3N2)
1918: “Spanish Flu” 1957: “Asian Flu” 1968: “Hong Kong Flu”
20-40 million deaths 1-4 million deaths 1-4million deaths
Credit: US National Museum of Health and Medicine
Total population of the SEA Region = 1.5 billion
Total population at risk = 1.3 billion (87%)
DF/DHF re-emerging infectious diseases
No report
Sou
rce:
FA
O
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
• Anticipation/Prediction• Preparedness• Early warning/Surveillance• Effective and co-ordinated response• Evaluation
Components of Effective Outbreak Management
• Anticipation/Prediction• Preparedness• Early warning/Surveillance• Effective and co-ordinated
response• Evaluation
Reported cases of encephalitis in Nepal, 1997-1998: Prediction/trends
0
50
100
150
200
250
300
350
1 5 9 13 17 21 25 29 33 37 41 45 49
Week No
Cas
es
1997
1998
Source: EWARS
Co
mp
osi
te r
ain
y d
ays
x r
ain
fall
su
rplu
s (1
2 m
on
th a
ccu
mu
late
d f
igu
re) RVF EPIZOOTICS
Davies et al. 1985. Bull. WHO. 63:941-3.
Effect of rainfall in producing RVF Epizootics in Kenya 1950-1982:
Forecast/Metrological Data
Components of Effective Outbreak Management
• Anticipation/Prediction• Preparedness• Early warning/Surveillance• Effective and co-ordinated
response• Evaluation
• What should be done ?
• Who should do it ?
• What resources or supplies will be required ?
Epidemic Preparedness and Response
Plan
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
• 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 ?
• 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 periodNeed to establish trend
Absolute rate over a period Population at risk and index cases (2/100,000)
Statistical cut-offs Time series modeling (deviations)
0
10
20
30
40
50
60
70
80
90
DAY
CASES
Labconfirmation
Outbreak Detection and Response: no functional EWS
Response
Opportunity for control
Detection/Reporting
First Case
0
10
20
30
40
50
60
70
80
90
DAY
CASES
Outbreak Detection and Response: functional EWS
First Case
Detection/Reporting
Confirmation
Response
Opportunity for control
How can early warning systems contribute to outbreak management ?
• 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
Number of outbreaks reported under the drought management information system available form the SRC's office, Orissa
0
2
4
6
8
10
12
14
16
1/3
1
2/1
5
2/2
8
3/1
5
3/3
1
4/1
5
4/3
0
5/1
5
5/3
1
6/1
5
6/3
0
7/1
5
7/3
1
8/1
5
8/3
1
9/1
5
9/3
0
10/1
5
10/3
1
11/1
5
11/3
0
12/1
5
12/3
1
Fortnight end date
Nu
mb
er
of
ou
tbre
ak
s r
ep
ort
ed
Mapping of Reported Disease Outbreaks, Orissa, MIS/OMDSS, 2003
Components of Effective Outbreak Management
• Anticipation/Prediction• Preparedness• Early warning/Surveillance• Effective and co-ordinated
response• Evaluation
Confirm outbreak and diagnosis
Diagnosis verified ? clinical + laboratory
Link between cases?Expected numbers?
DetectionRoutine surveillanceClinical / LaboratoryGeneral publicMedia
Outbreak confirmed
Further investigation?
Immediate control measures?
Control can happen at any time during the outbreak! But you still
may need to investigate
0
5
10
15
20
25
1 3 5 7 9 11 13 15 17 19
0
5
10
15
20
1 5 9 13 170
5
10
15
20
1 4 7 10 13 16 19
Examples of epidemic curves
Point source
Continuing common source Multiple waves -person to person or further outbreak
Post outbreak Tasks
• Prepare written report
• Communicate public health messages
• Convince public health policy
• Evaluate performance
PREPAREDNESS OUTBREAK CONTROL
Detect & Confirm
Investigate
Analyse
Respond
Evaluate
Predict & Prevent
TreatControl
CommitteePriorities
PlanCo-ordination
ResponsibilitiesResourcesSuppliesTraining
SurveillanceRapid Response
Attributes: detection, alert, response • 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
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
Recommended