Transcript Slide 1

Principles of Surveillance
Lazareto de Mahón, Menorca, Spain
9th October 2006
EPIET 2004; Denise Werker
EPIET 2005; Suzanne Cotter
EPIET 2006; Susan Hahné
Content
 aim of lecture
 context, definitions and history of surveillance
 the process
 aims of surveillance
 criteria for undertaking surveillance
 surveillance versus research
 steps in setting up 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
Context (1)
Surveillance in EPIET Introductory Course
Presentations
 Principles of surveillance
Problem-based exercises
 Secular trends
 Surveillance
– set up surveillance
– analytic tools for surveillance
– evaluation of surveillance systems
Context (2)
Intervention Epidemiology
 Surveillance
 Outbreak investigation
 Applied epidemiological research
Context (3)
Control of Communicable Diseases: Tools
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isolation
treatment
disinfection & barriers
quarantine & surveillance
vaccination
prophylaxis
Context (3)
Control of Communicable Diseases: Tools
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isolation
treatment
disinfection & barriers
quarantine & surveillance
vaccination
prophylaxis
‘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’
Definition - dictionary
Surveillance
n. Close observation, especially of a suspected
spy or criminal
ORIGIN C19: from Fr., from sur- 'over' + veiller
'watch'
Source: The Concise Oxford Dictionary. Ed. Pearsall J. Oxford University Press, 2001.
Definition – epidemiology (1)
Surveillance
“The continuing scrutiny of
all aspects of occurrence and spread of disease
that are pertinent to effective control”
Source: Last JM. A Dictionary of Epidemiology (Second Edition). Oxford University Press 1988, New York.
Definition – epidemiology (2)
Surveillance
“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”
Source: Alexander Langmuir (1910 – 1993)
Historical perspective (1)
First use for Public Health Action
William Farr (1807 – 1883)
 Superintendent, statistical department, General
Register Office, England and Wales
 Collected, analysed, interpreted vital statistics
 Plotted rise and fall of epidemics of infectious
diseases, identifying associations
 Disseminated information in weekly, quarterly,
and annual reports, medical journals, public
press
Historical perspective (2)
Recognition by World Health Organization
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"
Surveillance is a cyclical process
Health Care System
Public Health Authority
Reporting
Event
Real world! …
expected
changes
Capture
Data
Analysis &
Interpretation
Dissemination
Intervention
Information
Aims of Surveillance (1)
Actions: examples
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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
Aims of Surveillance (2)
Public Health aims
 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
- make decisions regarding interventions
 Stimulate or inform research
- generate hypotheses, inform methodologie
Criteria for undertaking surveillance
Public Health importance / rationale
 burden of disease (incidence / prevalence)
 severity, mortality
 epidemic potential, threat
 costs, socio-economic impact
 preventability / opportunities for control
 public concern and news-worthiness
Feasibility
 costs
 availability of data
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
Steps in setting up surveillance (1)
1. Understand the problem
2. Identify opportunities for prevention &
control
- interventions
- target audience
3. Set objectives
4. Specify requirements to meet objectives
5. Design
- case definitions & indicators
- data needed
- data sources
- data transfer
Steps in setting up surveillance (2)
5. Translate information into action
- analyse
- interpret
- disseminate
6. Evaluate surveillance system
1. Understand the problem
Transmission Environment
Exposure
Vector
Direct
Source of
infection
Infection
Disease
Recovery
Death
Disability
Reservoir
2. Identify opportunities for prevention & control
Transmission
Exposure
Environment
Vector
6. Prevent transmission
e.g. universal precautions
1. Vaccination
Direct
Source
infection
4. Isolation/ treatment
Infection
5. Ecological Management
2. Prophylaxis
Disease
3. Treatment
Recovery
Death
Disability
Reservoir
2. Identify opportunities for prevention & control
Target audiences
 Public Health professionals
 Government / Politicians
 Clinicians / Microbiologists / Control of
Infection staff
 Environmental Health professionals
 Health service managers
 Health educators / teachers
 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. Requirements of the system
Keep it as simple as possible!!
 Timeliness
 Sensitivity
 Specificity
 Completeness of information
 Representativeness
 Acceptability
5. Design – case definitions
Report
Lab confirmed
Clinical specimen
Seek medical attention
Symptoms
Infected
Exposed
5. Design – examples of data needed
 Numerators
- number of cases
- number of resistant strains
 Denominators
- population under surveillance
- life births (CRS)
- bacterial isolates (AMR)
5. Design – data sources (1)
 Health service
– notifications
– laboratories
– disease registries
– community services
– emergency services
– screening programmes (antenatal, blood
donors)
– pharmacy / over the counter drugs
– vaccination programmes
5. Design – data sources (2)
 Veterinary
– animals (domestic, wild)
– food
 Environment
– water
– food
– air
 Population statistics
– deaths
– denominators
5. Design – data sources (3)
Issues
 cost
 representativeness
 comparability
 confidentiality
 acceptability
 data quality
 timeliness
 commercial sensitivity
5. Design – data transfer
 Existing infrastructure
 Methods
– web-based
– telephone
 Frequency
 Zero reporting
5. Design – addition design issues
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Sampling vs. comprehensive
Aggregated vs. individual data
Active vs. passive
Statutory vs. voluntary
Confidential vs. anonymous
Security
6. Information into Action (1)
 Analysis
– descriptive (time, place, person)
– time series
– outbreak detection
– molecular epidemiology
– geographical information
systems (GIS)
 Interpretation
– system and data characteristics and changes
– chance, bias, truth
6. Information into Action (2)
 Dissemination of information
– develop outputs in consultation with users
– appropriate level of detail for action
– regular review of usefulness
– avoid information overload
7. Evaluation of surveillance system
Did the system do what it set out to do?
Surveillance – the 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
Surveillance – the 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
– ‘information for action’
 General process
– capture
– analysis
– dissemination
 Aims
 Criteria to set up surveillance system
– public health importance
– feasibility
– difference between surveillance and research
 Different steps
 Challenges and opportunities
Thank you!