Principles of Surveillance

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Principles of Surveillance

• Lazareto de Mahón, Menorca, Spain
• 9th October 2006

EPIET 2004 Denise Werker EPIET 2005 Suzanne
Cotter EPIET 2006 Susan Hahné
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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

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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

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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

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Intervention Epidemiology
Context (2)

• Surveillance
• Outbreak investigation
• Applied epidemiological research

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Control of Communicable Diseases Tools
Context (3)

• isolation
• treatment
• disinfection barriers
• quarantine surveillance
• vaccination
• prophylaxis

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Control of Communicable Diseases Tools
Context (3)

• 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
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Surveillance
Definition - dictionary

• 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.

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Surveillance
Definition epidemiology (1)

• 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.
•  

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Surveillance
Definition epidemiology (2)

• 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)

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First use for Public Health Action
Historical perspective (1)

• 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

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Recognition by World Health Organization
Historical perspective (2)

• 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"

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Surveillance is a cyclical process
Health Care System
Public Health Authority
Reporting Capture
Data
Event
Real world! expected changes
Analysis Interpretation
Information
Intervention
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Actions examples
Aims of Surveillance (1)

• 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

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Public Health aims
Aims of Surveillance (2)

• 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

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Public Health importance
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

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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

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Steps in setting up surveillance (1)

• Understand the problem
• Identify opportunities for prevention control
• - interventions
• - target audience
• Set objectives
• Specify requirements to meet objectives
• Design
• - case definitions indicators
• - data needed
• - data sources
• - data transfer

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Steps in setting up surveillance (2)

• Translate information into action
• - analyse
• - interpret
• - disseminate
• Evaluate surveillance system

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1. Understand the problem
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2. Identify opportunities for prevention control
Transmission
Source infection
Reservoir
Recovery
Death
Disability
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Target audiences
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

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SMART
3. Set objectives

• Specific
• Measurable
• Acceptable and Action oriented
• Realistic
• Time related

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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

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4. Requirements of the system

• Keep it as simple as possible!!
• Timeliness
• Sensitivity
• Specificity
• Completeness of information
• Representativeness
• Acceptability

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5. Design case definitions
Report
Lab confirmed
Clinical specimen
Seek medical attention
Symptoms
Infected
Exposed
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5. Design examples of data needed

• Numerators
• - number of cases
• - number of resistant strains
• Denominators
• - population under surveillance
• - life births (CRS)
• - bacterial isolates (AMR)

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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

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5. Design data sources (2)

• Veterinary
• animals (domestic, wild)
• food
• Environment
• water
• food
• air
• Population statistics
• deaths
• denominators

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5. Design data sources (3)

• Issues
• cost
• representativeness
• comparability
• confidentiality
• acceptability
• data quality
• timeliness
• commercial sensitivity

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5. Design data transfer

• Existing infrastructure
• Methods
• web-based
• telephone
• Frequency
• Zero reporting

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5. Design addition design issues

• Sampling vs. comprehensive
• Aggregated vs. individual data
• Active vs. passive
• Statutory vs. voluntary
• Confidential vs. anonymous
• Security

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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

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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

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7. Evaluation of surveillance system

• Did the system do what it set out to do?

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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

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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

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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

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Thank you!