1. Surveillance – an introduction
Preben Aavitsland

2. 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.

3. Surveillance – original use
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.
Until 1950s

4. Origins of surveillance
William Farr
collected, analysed, interpreted vital statistics,
plotted rise and fall of epidemics of infectious diseases
disseminated information in weekly, quarterly, and annual reports, medical journals, public press
s In Europe and USA doctors must reported communicable diseases
1923 Sanepid system started in the Soviet Union
1925 National surveillance system in USA

5. Towards a new concept 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
General practice of “epidemiologic intelligence”
In 1963

6. In the words of WHO World Health Assembly in 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"

7. Surveillance
Systematic ongoing collection, collation and analysis of data and the timely dissemination of information to those who need to know so that action can be taken.
Source: A Dictionary of Epidemiology. 4th edition. Ed. Last J. Oxford University Press, 2001

8. Surveillance
World Health Assembly 2005 with the new International Health Regulations
”The systematic ongoing collection, collation and analysis of data for public health purposes and the timely dissemination of public health information for assessment and public health response as necessary.”

9. Information for action!
Surveillance
Surveillance is the ongoing systematic collection, collation, analysis and interpretation of data; and the dissemination of information (to those who need to know) in order that action may be taken
Information for action!

10. Analysis, interpretation Feedback, recommendations
The surveillance loop
Health care system
Surveillance centre
Event
Action
Data
Information
Reporting
Analysis, interpretation
Feedback, recommendations

11. Rationale for surveillance
The disease
Severity
Frequency
Communicability
International obligations
Costs
Preventability
Society
Public and mass media interest
Will to prevent
Availability of data

12. Priority setting – which diseases?
Incidence / prevalence
Severity
Epidemic potential
Socio-economic impact
Cost
Preventability
Public concern and news-worthiness
Feasibility

13. Possible objectives of surveillance
Monitor trends (by time, place, person)
towards a control objective
as programme performance
as intervention evaluation
Detect outbreaks
Estimate future disease impact
Collect cases for further studies
….in order to [action]

14. Actions resulting form surveillance
…in order to:
implement control measures (rapid response)
prioritise public health resources
design and plan public health programmes
plan and conduct research …

15. SMART objectives Specific Measurable Acceptable and Action-oriented
Realistic
Time-related

16. Examples Vague... To estimate the frequency of hepatitis C
To detect outbreaks of measles
Specific and action-oriented
To measure the incidence 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

17. Ex: To monitor progress towards polio eradication by monitoring the incidence of poliomyelitis where wild poliovirus is isolated in children under 14 years
Cases of poliomyelitis where wild poliovirus was isolated
in children in a rural district,

18. Ex: To measure the incidence of AIDS to predict future trends and facilitate health service planning
Cases of AIDS in a city district,

19. Ex: To monitor trends in the proportion of resistant gonorrhoea in order to guide empiric antibiotic therapy
Incidence of gonorrhoea and proportion with PPNG in Norway

20. Analysis, interpretation Feedback, recommendations
The surveillance loop
Health care system
Surveillance centre
Event
Action
Data
Information
Reporting
Analysis, interpretation
Feedback, recommendations

21. Event and population under surveillance
Population and time
Everyone in the country or defined part of the country
Patients in hospitals
Employees in a factory
All children in the winter months …
Event
Disease
Syndrome
Accute flaccid paralysis
Influenza-like illness
Diarrhoea
Infection
Public health issue
Antimicrobial resistance
Environment
Vector population
Water quality …

22. Seek medical attention
Diagnosis
Pos. specimen
Clinical specimen
Seek medical attention
Symptoms
Infected
Exposed

23. Seek medical attention
Diagnosis
Lab-confirmed disease
Pos. specimen
Clinical specimen
Severe disease
Seek medical attention
Syndrome
Mild disease
Symptoms
Asymptomatic infection
Infected
Exposed

24. What is better: A system based on clinical cases or a sysem based on laboratory confirmed cases?

25. Indicators
A calculated measure that indicates the changes you want to monitor
Decide one or more indicators that sums up the surveillance results
For example
Number of cases
Number of cases per population per year (incidence rate)
Percentage children under 1 year among meales cases
Median age at first sexual intercourse
Percentage unemployed among 50 year olds

26. Analysis, interpretation Feedback, recommendations
The surveillance loop
Health care system
Surveillance centre
Event
Action
Data
Information
Reporting
Analysis, interpretation
Feedback, recommendations

27. Case definition
Includes
(Time, place, person)
Clinical features
and /or
Laboratory results
and/or
Epidemiological features
Should be
Clear, simple
Field tested
Stable and valid
Ex. Meningococcal disease is any person with symptoms of meningitis or septicaemia and Neisseria meningitidis detected from blood or cerebrospinal fluid by culture or PCR.

28. Sensitivity versus specificity
The role of lab, cmpylobacteriose i Vest-Agder

29. Sensitivity versus specificity

30. Sensitivity and predicitive value
= reported true cases total true cases
= proportion of true cases detected
Positive predictive value
= reported true cases total reported cases
= proportion of reported cases are true cases

31. The tiered case definition
Confirmed
The role of lab, cmpylobacteriose i Vest-Agder
Probable
Possible

32. Features of different definitions
“Confirmed” (specific) case-definition
low sensitivity - includes few cases
high specificity - includes mostly true cases
few false positive cases
“Possible” (sensitive) case-definition
high sensitivity - includes almost all cases
low specificity - includes also many non-cases
many false positive cases

33. Seek medical attention
Diagnosis
Confirmed case
Pos. specimen
Clinical specimen
Seek medical attention
Probable case
Symptoms
Infected
Exposed

35. Do you want a mainly sensitive or a mainly specific case definition for measles?

36. Case definitions and reporting criteria
Measles
Confirmed nnn nnn nnnn nn
Probable nn nnn nnn nnnn
Possible nnnnnn nn n nnn
Reporting criteria
”Measles”
Output Measles

37. Analysis, interpretation Feedback, recommendations
The surveillance loop
Health care system
Surveillance centre
Event
Action
Data
Information
Reporting
Analysis, interpretation
Feedback, recommendations

38. Data sources Hospitals Ambulatory clinics General practitioners
Clinics for sexually transmitted diseases
Laboratories
Selected sites - sentinel surveillance system
Schools
Work places
Existing data collection systems (death certificates, sick leave system etc)
Public sector
Private sector
Non-governmental organisations

39. Seek medical attention
Hospitals
Diagnosis
Laboratories
Pos. specimen
Clinical specimen
General practitioners
Seek medical attention
Schools, work places
Symptoms
Infected
Exposed

40. Issues with differen data sources
Cost
Representativeness
Acceptability
Data quality
Timeliness
Confidentiality

41. Data collection instrument
Data form or no specified format?
Open or closed questions?
Data requirements specified?
Reporting form
Copy
Database
Reporting form
Interpretation
Database

42. Information versus acceptability

43. Aggregation of data Individual data Aggregated data
Identified – name, personal id number
Non-identified – but possible to trace back
Anonymous – impossible to trace back
Aggregated data
Numbers
Tabulated numbers – by sex, age group etc

44. Reporting (data transfer)
Data transfer method
Paper by mail
Telephone
Telefax
Internet
Protected net
Data transfer frequency
For every case
Daily
Weekly
Monthly
Zero reporting

45. Active versus passive surveillance
Wait for reporters to report
May have low sensitivity
Used in most surveillance systems
Active
Reach out to potential reporters regularly
More sensitive
More resource-demanding
Used for special diseases or periods

46. Quality checking Reporting regularity Report quality
Follow up procedures

47. Analysis, interpretation Feedback, recommendations
The surveillance loop
Health care system
Surveillance centre
Event
Action
Data
Information
Reporting
Analysis, interpretation
Feedback, recommendations

48. Data analysis and interpretation
From data to indicators to interpretation
Data validation (completeness + validity)
Descriptive analysis: time, place, person
Generating and testing hypotheses related to time, place, person
Advanced analyses
Time series analysis
Cluster analysis
Interpretation
Using supporting information

49. Analysis, interpretation Feedback, recommendations
The surveillance loop
Health care system
Surveillance centre
Event
Action
Data
Information
Reporting
Analysis, interpretation
Feedback, recommendations

50. Information and feedback
Contents
Surveillance information
Interpretations
Recommendations
Other information
Format
Text
Tables
Figures
Target audience
Public
Professionals
Policy makers
Medium
Newsletter
Paper
Fax
Internet
Web-tool
Frequency
Immediately
Daily
Weekly
Monthly

51. Web tool – example from Norway

52. Feedback has its own value
Shows respect for those who report
Increases adherence to system
Forces you to analyse and interpret

53. What is the feedback from the surveillance system in your country?

54. Analysis, interpretation Feedback, recommendations
The surveillance loop
Health care system
Surveillance centre
Event
Action
Data
Information
Reporting
Analysis, interpretation
Feedback, recommendations

55. Information for action!
Surveillance is not for archives!
Action
implement control measures
rapid response
prioritise public health resources
policy change?
design and plan public health programmes

56. If there is no action..
..it isn’t surveillance

57. Ethical issues: right or wrong
Build trust between public health practitioners and the society
Issues:
Self-interest or desire to benefit society?
Potential benefits and harms. For whom?
Maximise benefits. Minimise harms
Involvement of community representatives
Rights of people
Confidentiality – share only with those who have permission from patient or legal right to know
Respect for people

58. Legal issues
Surveillance systems should have a legal foundation that specifies
How to collect information
How to use information
Not for other purposes
How to safeguard and store information
How to allow individuals to see and correct information
Main principles
Collect only what you need
Choose the lowest level of identification needed
Analyse and publish rapidly

59. Functions Who does what? Core functions Detection Reporting
Investigation & confirmation
Analysis & interpretation
Action/response
Support functions
Training
Supervision
Resources
Standards/guidelines
Who does what?

60. Resources for system operation
Funding sources
Personell time
Other costs
Training
Mail
Forms
Computers
...

61. Your most important assets
A good network of motivated people
Clear case definition and reporting mechanism
Efficient communication system
Basic but sound epidemiology
Laboratory support
Good feedback and rapid response
Rapid reporting  Analysis Action

62. Identify two major weaknesses in the surveillance system for communicable diseases in your country

63. Evaluation of surveillance systems
Systematic investigation of the merit of the surveillance system in order to increase its usefulness and efficiency

64. Importance of evaluating surveillance systems
Quality
Often neglected
Basis for improvements
Obligation
Does the system deliver?
Credibility of public health service
Learning process
”Do not create one until you have evaluated one”

65. General framework for evaluation
A. Engagement of stakeholders
B. Evaluation objective
C. System description
D. System performance
E. Conclusions and recommendations
F. Communication

66. C. System description 1 Public health rationale (why?)
2 Objectives (what?)
3 Operations (how?)
4 Resources (how much?)
Extreme learning value!!!!

67. D. System performance Is it useful? Use of information Does it work?
System attributes
Simplicity
Flexibility
Data quality
Acceptability
Sensitivity
Positive predictive value
Representativeness
Timeliness
Stability
Is it useful?
Use of information
Users
Actions taken
Link to objectives

68. Timeliness

69. E. Conclusions and recommendations
Proper rationale?
Attributes
Balance of attributes and costs
Fulfilling objectives?
Recommendations
Continue
Revise: specify
Stop

70. Surveillance – a big challenge
Crude
Inaccurate
Incomplete
Cumbersome
Complex