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Principles of Surveillance
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
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
Aim
Surveillancen. 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 - dictionary
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 (1)
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)
Definition – epidemiology (2)
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
First use for Public Health Action
Historical perspective (1)
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"
Recognition by World Health Organization
Historical perspective (2)
Health Care System Public Health Authority
Event Data
InformationIntervention
Reporting
Capture
Analysis & Interpretation
Real world! … expected changes
Dissemination
Surveillance is a cyclical process
detect outbreaks early warning design/change vaccination policy design policy re antimicrobial resistance evaluate interventions to improve them certify elimination / eradication
Aims of Surveillance (1)
Actions: examples
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
Aims of Surveillance (2)
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
Criteria for undertaking surveillance
Public Health importancePublic Health importance / rationale
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
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 (1)
5. Translate information into action
- analyse
- interpret
- disseminate
6. Evaluate surveillance system
Steps in setting up surveillance (2)
Disease
DeathDisability
Recovery
Source of infection
Transmission
Reservoir
Vector
Environment
Direct
Exposure
Infection
1. Understand the problem
Infection
Disease
DeathDisability
Recovery
Source infection
Transmission
Reservoir
Vector
Environment
Direct
3. Treatment
4. Isolation/ treatment
2. Prophylaxis
6. Prevent transmission e.g. universal precautions
5. Ecological Management
Exposure
1. Vaccination
2. Identify opportunities for prevention & control
Public Health professionals Government / Politicians Clinicians / Microbiologists / Control of
Infection staff Environmental Health professionals Health service managers Health educators / teachers Public
2. Identify opportunities for prevention & control
Target audiences
Specific Measurable Acceptable and Action oriented Realistic Time related
3. Set objectives
SMART
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
Exposed
Clinical specimen
Symptoms
Lab confirmed
Infected
Seek medical attention
Report
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
5. Design – data transfer
Existing infrastructure
Methods– web-based
– telephone
Frequency
Zero reporting
Sampling vs. comprehensive Aggregated vs. individual data Active vs. passive Statutory vs. voluntary Confidential vs. anonymous Security
5. Design – addition design issues
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 (1)
Dissemination of information– develop outputs in consultation with users– appropriate level of detail for action– regular review of usefulness– avoid information overload
6. Information into Action (2)
Did the system do what it set out to do?
7. Evaluation of surveillance system
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 challenges
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
Surveillance – the opportunities
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
Summary
Thank you!