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
isolation
treatment
disinfection & barriers
quarantine & surveillance
vaccination
prophylaxis
Context (3)
Control of Communicable Diseases: Tools
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
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
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
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
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!