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Event based surveillance systems
Alicia Barrasa
Introductory course 2012
Lazareto, Menorca, Spain
Infectious diseases
• Arise from many different pathogens: viruses, bacteria, parasites
• Spread in many different species: humans, insects, domestic and wild animals, aquatic animals and sometimes breach barrier between animal and humans (70% of emerging infections arise from animal population)
• Take many different routes of transmission: direct contact, vectors, food, environmental
• Affect all populations in all regions of the world
Emerging and Re-emerging infectious diseases
Cryptosporidiosis
Dengue haemhorrhagic feverCholera
E. coli O157
Typhoid
Diphtheria
E. coli O157
Lassa fever
Dengue haemhorrhagic fever
Cholera
Multidrug resistant Salmonella
E.coli non-O157Malaria
Legionnaire’s disease
Buruli ulcer
Shigellosis
Typhoid
Shigellosis
Cholera O139
Respiratoryinfection
Kyasanur f.Lyme Borreliosis Reston
Venezuelanequine encephalitis
West Nile Fever
EchinococcosisYellow fever
Ebola haemorrhagicfever Human
monkeypox
Influenza A (H5N1)
RVF/VHF
Ross River virus
Hendra virus
BSEWest Nile Virus
Nipah Virus
SARS
Human monkepox
O’nyong-nyong fever
Reston Virus
Rabies
nvCJD
Epidemic Alert and Response (EAR), WHO Regional Office for Europe
A(H1N1)v
Accidental and deliberate release of infectious agents
• Increased research, biotechnology is widely available
• Increased risk for accidental release (e.g. SARS 2004 from laboratory)
• World tensions remain and the deliberate release of infectious agents is no longer a remote threat.
International Health Regulation1374 Venice Quarantine for Plague1851 Paris 1st International Sanitary Conference1947 Geneva WHO Epidemiological Information
Service1951 Geneva International Sanitary Regulations1969 Geneva International Health Regulations
2004 Regional consultationsNov 2004 Geneva Intergovernmental Working
Group meetingFeb 2005 Geneva Intergovernmental Working
Group meetingMay 2005 Geneva Revised IHR, World Health
Assembly adopted
4 diseases that always have to be notified polio (wild type virus), smallpox, human influenza caused by a novel virus, SARS.
Diseases that always lead to the use of the algorithm : cholera, pneumonique plague, yellow fever, VHF (Ebola, Lassa, Marburg), WNF, meningitis, others
*Q1: serious graves repercussions for public health?
Q2: unusual or unexpected?
Q3: risk of international spread?
Q4: risk of travel or traffic restrictions?
Insufficient information : re-evaluate
IHR Decision Instrument
IHR Decision Instrument
International Health Regulation - 2005To decide on need for notification any public health event can be assessed by the criteria
• Is the public health impact of the event serious?
• Is the event unusual or unexpected?
• Is there a significant risk of international spread?
• Is there a significant risk of international travel or travel restrictions ?
Obligation to establish core capacities:
• Surveillance
• Response
Epidemic Intelligence
• Definition
– The systematic collection and collation of information from a variety of sources, usually in real-time, which is then verified and analysed and, if necessary, activates response
• Objective
– to speed up detection of potential health threats and allow timely response
Epidemic Intelligence - ECDC
• Establish procedures for the identification of emerging health threats in cooperation with MS
• Identify, assess and communicate current and emerging communicable disease threats
• Inform EC and MS about emerging health threats requiring their immediate attention
• Communication on emerging health threats, including to the public
Surveillance is
Information for action
Epidemic Intelligence
Data EventsCollectAnalyseInterpret
Screen/collectFilterValidate
AssessInvestigate
Signal
Response
Public health Alert
Event monitoring“Surveillance” systems
Event-based surveillanceIndicator-based surveillance
Indicator based Surveillance
Surveillance systems• Ongoing and systematic
– Collection and analysis of data – Interpretation and dissemination of results
related to health events of interest
• For action– Describe diseases– Outbreak detection– Monitor changes /interventions– Provide evidence for policy making – Generate hypothesis
Event based Surveillance
Organized and rapid capture of information about events that are a potential risk to public health:
• Events related to the occurrence to the disease in humans (clusters, unusual patterns, unexpected deaths…)
• Events related to potential exposures (diseases in animals, contaminated food or water, environmental hazards…)
Need confirmation
Indicator vs event based
Indicator based Event based
Definitions - Clinical presentation
- Characteristics of people
- Laboratory criteria
- Specific
- ...events that are a potential risk
- ...unusual events in the community
- Sensitive
Timeliness - Weekly / monthly
(some may be immediate)
- Possible delay between identification and notification
- All events should be reported to the system immediately
- Real time
Indicator vs event based
Indicator based Event based
Actors - Involved in the system - Might not know
Reporting structure
- Clearly defined
- Reporting forms
- Reporting dates
- Teams to analyse data at regular intervals
- No predefined structure
- Reporting forms flexible for quali and quantitative data
- At any time
- Teams to confirm evens and prepare the response
Indicator vs event based
Indicator based Event based
Trigger for action
- a pre-defined thresholds - a confirmed event
Response - depends on the delay between identification, data collection and analysis
- depends on the confirmation of the event, but ideally is immediate
Epidemic Intelligence
Data EventsCollectAnalyseInterpret
Screen/collectFilterValidate
AssessInvestigate
Signal
Response
Public health Alert
Event monitoring“Surveillance” systems
Event-based surveillanceIndicator-based surveillance
Epidemic Intelligence - ECDC
The process of Epidemic Intelligence
1. Screening/collecting
2. Filtering
3. Validating
4. Analysis
5. Assessment
6. Documentation
7. Communication
Screening / Collecting:
Monitoring known threats and detecting new threats by screening a virtually unlimited amount of information.
web-based early warning systems
Sophisticated applications able to gather, filter and classify web-based information for public health purposes
• Advantages Disadvantages
Automatic systems little or no human intervention
near real time information
False positive component, duplication, overload for analysts
Moderated systems rely on human moderation
analysts reduce redundancy and false positive
Time delay, human selection bias
Filtering:
The objective of filtering is to decide which information detected through screening might be potential public health events of National, European or international concern.
Early detection
Validation:
This is the process of confirming the accuracy and credibility of information received from non-official sources (unverified information).
Early detection
Identification of signals
Analysis:
Initial evaluation based on preliminary info available in terms of likelihood and of possible human public health impact
Risk Assessment
Documentation:
Logging information and actions taken during the EI process from the beginning is a crucial action to analyse the ongoing situation and to trace back all the steps
Communication:
To public/media and to scientific community about findings and assessment of potential public health events detected and investigated
Epidemic Intelligence - ECDC
A small summary
• Indicator and event based systems are tools for PH Surveillance
• event based systems have already been successfully used
• The challenge: confirmation of the events
Epidemic Intelligence at ECDC• 24/7 Screening of news from different sources• Round table
– Daily threat assessment– Daily & weekly reports– Communication
• Risk assessment• Response to outbreaks
WHO. The revision of the International Health Regulations. Wkly Epidemiol Rec 1996; 71: 233-5
WHO. Revision of the International Health Regulations: progress report, January 1998. Wkly Epidemiol Rec 1998; 73: 17-9
Paquet C, Coulombier D, Kaiser R, Ciotti M. Epidemic intelligence: a new framework for strengthening disease surveillance in Europe. Euro Surveill. 2006;11(12):665
WHO. A guide to establishing event-based surveillance http://www.wpro.who.int/internet/resources.ashx/CSR/Publications/eventbasedsurv.pdf
… to know more …
Thank you for your attention