Principles of Surveillance
Lazareto de Mahón, Menorca, Spain
11 October 2011
Katharina Alpers (2009), Martin Donaghy (2008), Susan Hahné (2007, 2006),
Suzanne Cotter (2005), Denise Werker (2004)
Content
 aim of lecture
 surveillance: context, definitions and history
 aims of surveillance
 the process
 surveillance versus research
 steps in setting up surveillance
 criteria for undertaking surveillance
 challenges & opportunities
 summary
Aim
After the lecture, you should be able to…
Define:
 surveillance
 its three main components
Describe:
 the contexts / historical perspective of surveillance
 possible aims
 criteria for undertaking surveillance
 the difference between surveillance and research
 the different steps in setting up surveillance
 some challenges and opportunities
Intervention Epidemiology
 Surveillance
 Outbreak investigation
 Applied epidemiological research
Surveillance in EPIET Introductory Course
Lectures
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Principles of surveillance
Event-based surveillance
Analytical tools in surveillance
Evaluation of a surveillance system
H1N1 surveillance in Europe
Case studies
 Implementation of H1N1 surveillance
 Surveillance data analysis
 Evaluation of surveillance systems
The Concise Oxford Dictionary
n. Close observation, especially of a suspected
spy or criminal
ORIGIN French, from sur- 'over' + veiller 'watch'
Source: The Concise Oxford Dictionary. Ed. Pearsall J. Oxford University Press, 2001.
Tools for Control of Communicable Diseases
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isolation
treatment
vaccination
prophylaxis
disinfection
quarantine
surveillance
‘Close observation of individuals
suspected of incubating serious infectious diseases
in order to detect initial symptoms of disease
in time to institute treatment and isolation’
First use of data for Public Health Action
William Farr (1807 – 1883)
 Superintendent of statistical department,
General Register Office, England and Wales
 Collected, analysed, interpreted vital statistics
 Described epidemics of infectious diseases
 Drew conclusions, made recommendations
 Disseminated information
Definition by Alexander Langmuir
(1910 – 1993)
“Continued watchfulness
over the distribution and trends of incidence,
through
the systematic collection, consolidation and evaluation
of morbidity and mortality reports and other relevant data
together with the timely and regular dissemination
to those who need to know”
21st World Health Assembly (1968)
 Systematic collection of pertinent data
 Orderly consolidation and evaluation of these
data
 Prompt dissemination of the results to those who
need to know
"Information for action"
Aims of Surveillance
 Assess public health status (monitor trends,
detect outbreaks)
- prevent and control disease
 Define public health priorities
- plan considering impact of hazard, exposure, disease
 Evaluate public health programmes
- take decisions regarding interventions
 Stimulate or inform research
- generate hypotheses, inform methodologie
Examples for Interventions
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manage contacts of a case
detect outbreaks
early warning
design/change vaccination policy
design policy re antimicrobial resistance
evaluate interventions to improve them
certify elimination / eradication
Surveillance is a cyclical process
Health Care System
Public Health Authority
Reporting
Event
Real world! …
expected
changes
Capture
Data
Analysis &
Interpretation
Dissemination
Intervention
Information
Surveillance versus Research
Surveillance
 Applies existing knowledge to guide health
authorities in the use of known control measures
 Directly relevant to monitoring and control needs
Research
 Pursues new knowledge from which better
control measures will result
 Systematic investigation, testing and evaluation,
designed to develop or contribute to knowledge
What we have seen so far
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Contexts of surveillance
Historical perspective
Definitions
Aims
Three main components
Surveillance versus research
Steps in setting up surveillance (1)
1. Understand the problem
2. Identify opportunities for prevention &
control
- interventions
- target audience
3. Set objectives
4. Specify attributes to meet objectives
5. Design
- case definitions & indicators
- data needed
- data sources
- data transfer
Steps in setting up surveillance (2)
6. Translate information into action
- analyse
- interpret
- disseminate
7. Evaluate surveillance system
1. Understand the problem
- Criteria for priority setting
Public Health importance
 burden of disease (incidence / prevalence)
 severity, mortality
 epidemic potential, threat
 costs, socio-economic impact
 preventability / opportunities for control
 intervention programme in place
 public concern and news-worthiness
Feasibility
 costs
 availability of data
2. Opportunities for intervention
Transmission
Exposure
1. Vaccination
6. eg. hygiene precautions,
vector control
Source
infection
Infection
2. Prophylaxis
4. Isolation/ treatment
Disease
5. Ecological Management
3. Treatment
Recovery
Death
Disability
Reservoir
3. Target audiences
 Public Health professionals
 Government / Politicians
 Clinicians / Microbiologists / Control of Infection
staff
 Environmental Health professionals
 Health service managers
 Health educators / teachers
 NGOs
 Public
3. Set objectives
SMART
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Specific
Measurable
Acceptable and Action oriented
Realistic
Time related
3. Set objectives - examples
Vague...
 To estimate the prevalence of hepatitis C
 To detect outbreaks of measles
Specific, measurable, action-oriented & timed
 To assess the prevalence of hepatitis C in
France in order to allow planning of specific
health care needs for the coming 20 years
 To detect early time and place clustering of
measles cases in order to ensure timely control
of outbreaks
4. Attributes of the system
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Timeliness
Sensitivity
Specificity
Completeness of information
Representativeness
Acceptability
Keep it as simple as possible!!
5. Design – options
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Sentinel vs. comprehensive
Aggregated vs. individual data
Active vs. passive
Statutory vs. voluntary
Confidential vs. anonymous
Basic vs enhanced
Indicator based versus event based
Security
5. Design – examples of data needed
 Numerators
- number of cases
- number of resistant strains
 Denominators
- population under surveillance
- live births (CRS)
- bacterial isolates (AMR)
5. Design – case definitions
Report
Lab confirmed
Clinical specimen
Seek medical attention
Symptoms
Infected
Exposed
5. Design – data set
 Case Definition
-Confirmed – Positive laboratory result
-Probable – Clinical + epidemiological link to confirmed case
-Possible - Clinical symptoms and signs
 Demographics
-Person, place and time
 Risk Factors
-Exposures
-Behaviours
Administrative
-Time reported
-Source
5. Design – issues
 cost
 representativeness
 comparability
 confidentiality
 acceptability
 data quality
 timeliness
 commercial sensitivity
5. Design – data sources: health services
– Laboratories: frontline diagnostic, reference
– Clinical services: physicians,
hospital discharge data, disease registries
– Screening programmes
(antenatal, blood donors)
– vaccination programmes
– pharmacy / over the counter drugs
5. Design – other data sources
 Veterinary
– animals (domestic, wild)
– food
 Environment
– water
– food
– air
 Population statistics
– deaths
– denominators
5. Design – data transfer
 Existing infrastructure
 Methods
– Paper
– Telephone
– Electronic
– Web-based
 Frequency
 Zero reporting
6. Information for Action (1)
 Analysis
– descriptive (time, place, person)
– analytical
– time series
– outbreak detection
– molecular epidemiology
– geographical information
systems (GIS)
 Interpretation
– system and data characteristics and changes
– chance, bias, truth
– Public health significance
6. Information for Action (2)
Dissemination of information
– develop outputs in consultation with users
– Who needs to know what?
– timing
– appropriate level of detail
– regular review of usefulness
– avoid information overload
6. Dissemination of information
 Alerts
-National and local
-Europe: EWRS
-International: IHR
 Reports
-Bulletins
-Annual statements
-Scientific journals
 Internet
 Public
-media
7. Evaluation of surveillance system
Does the system do what it set out to do?
i.e. meet specified objectives:
 Contribute to achieving public health goals?
 Meet the needs of stakeholders to improve policy,
services, public understanding?
Challenges
 Surveillance or research needed?
 Reliability
– crude and inaccurate
– incomplete
– accurate denominators
 Sustainability
– victim of success of control
 New threats
– emerging infections
– bioterrorism
 Timeliness
 Human Rights / data protection
Opportunities
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Near patient testing
Less invasive diagnostics (oral fluid, urine)
New molecular typing methods
Electronic patient records
‘New’ data sources
Behavioural surveillance
Syndromic surveillance
On-line, web-based systems
– data entry
– dissemination of information
 ´New´ analysis methods
– GIS
– bio-informatics
– modelling
Summary
 Context
– communicable disease control
– epidemiology
 Definition
– systematic collection of data
– information for action
 Aims
 Process with 3 components
– capture
– analysis
– dissemination
 Difference between surveillance and research
 Criteria and steps to set up surveillance system
– public health importance
– feasibility
– information for action
 Challenges and opportunities