Outbreak Alert and Response Systems: a review February 2004 Ayana Yeneabat, MD, MPH Epidemiologist, WHO

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


• 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

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mu

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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




• 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




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




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

Documents

Outbreak Alert and Response Systems: a review February 2004 Ayana Yeneabat, MD, MPH Epidemiologist, WHO