2. 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
3. Surveillance: General principle
Health Care System Public Health Authority
Data Information
Decision
Action
Feedback
Reporting
Evaluation
Analysis &
Interpretation
4. Objectives of surveillance
• Epidemic (Outbreak) detection
• Monitoring trends in endemic disease
• Evaluating an intervention
• Monitor progress towards a control objective
• Monitor programme performance
• Epidemic (Outbreak) prediction
• Estimate future disease impact
5. Dysentery
Polio
Malaria
AIDS
Tuberculosis
To detect outbreaks of dysentery by monitoring the
incidence of cases of acute bloody diarrhoea
To monitor progress towards polio eradication by
monitoring the incidence of poliomyelitis where wild
poliovirus is isolated in children under 14 years
To monitor the incidence of laboratory confirmed malaria
including the incidence of disease due to P. falciparum
and associated antiparasitic resistance.
To measure the incidence of AIDS cases so that future
trends may be predicted and health services planned
To monitor the ability of the TB programme to detect
cases, ensure treatment completion and cure
Examples of Surveillance Objectives
6. To monitor the ability of a TB programme to
ensure treatment completion and cure
0
200
400
600
800
1000
1200
1400
1600
1994 1995 1996 1997
Cases
Completion
Cure
Treatment completion and cure in TB cases, 1994-1997
Objective:
7. Rationale for Disease Surveillance
(Priority)
• Public health importance of disease ?
– Diseases frequencies (mortality, morbidity,
disability, hospitalized, etc)
– Communicability
– Case Fatality Rate (CFR)
• Can public health action be taken ?
• Are relevant data easily available ?
• Is it worth the effort (money,
human resources)?
8. Type of Surveillance
Community Vs Hospital based
– Community based surveillance: if cases under surveillance taken from
the community
– Health Facility based surveillance: if cases under surveillance taken
from health facilities
Active Vs Passive Surveillance
– Active surveillance : if the data designed and collected by
persons/institution who need the information
– Passive surveillance: if the data designed and collected by other
persons/institution who need the information
Sentinel Surveillance:
– Use “sentinel” by efficient way in conducting surveillance of key
indicators in the area.
9. Is the disease a priority ?
What are the objectives of surveillance ?
(e.g. to monitor cases and deaths from
dengue fever so as to evaluate control measures)
What data will be required to generate the
indicators and what sources of data exist?
What disease indicators will be used ?
(e.g. the number of new cases of TB per 100,000 pop
+ the number of deaths in TB cases)
PRIORITY
OBJECTIVES
MINIMUM DATA
AND DATA
SOURCES
TARGET
POPULATION
What is the population in which we wish
to detect cases ? (e.g. all? high risk groups ..)
INDICATORS
10. Surveillance: Data
Health Care System Public Health Authority
Information
Decision
Action
HEALTH EVENT
•Disease
•Syndrome (e.g., AFP, jaundice, VHF)
•Public health issue (e.g., AMR)
•Environment (e.g., animal vector, water)
11. Surveillance: Data
Health Care System Public Health Authority
Information
Decision
Action
DATA SOURCE
•Notifiable disease reporting system
•Vital statistics
•Survey
•Laboratory
12. Surveillance: Data
Health Care System Public Health Authority
Information
Decision
Action
CASE DEFINITION
•Clinical/laboratory
•Levels (suspected, probable,
confirmed)
•Indicators
14. Surveillance: General principle
Health Care System Public Health Authority
Data Information
Decision
Action
Feedback
Reporting
Evaluation
Analysis &
Interpretation
15. Surveillance: Reporting
Health Care System Public Health Authority
Data Information
Decision
Action
Reporting
frequency
•immediate
•weekly
•monthly ...
17. Ministry
of Health
WHO
Peripheral level
Intermediate level
Central level
Regional/International level
Surveillance: Tasks
Detect
Treat
Report
Analyse
Investigate
Report
Respond
Feedback
Analyse
Investigate
Confirm
Respond
Plan and Fund
Feedback
Analysis and feedback
Support
Policy and targets
Funding
18. Ministry
of Health
WHO
Peripheral level
Intermediate level
Central level
Regional/International level
Surveillance: Data flow
Clinical
(suspected)
+ Supportive
laboratory data
+ epidemiological
link (probable)
Diagnostic
Laboratory
(confirmed)
Regional reference
laboratory
19. Surveillance: Analysis & Interpretation
Health Care System Public Health Authority
Data
Decision
Action
• Data characteristics
• Data validation
• Descriptive analysis
• Hypothesis generation
20. Surveillance: Analysis & Interpretation
Health Care System Public Health Authority
Data
Decision
Action
• Various sources of
notifications
•Various levels of quality
•Continuous data collection
subject to change
Data characteristics
21. Surveillance: Analysis & Interpretation
Health Care System Public Health Authority
Data
Decision
Action
• Missing values
• Bias
• Duplication
Data validation
22. Surveillance: Analysis & Interpretation
Health Care System Public Health Authority
Data
Decision
Action
• Time
• Place
• Persons
Descriptive analysis
23. Surveillance: Analysis & Interpretation
Health Care System Public Health Authority
Data
Decision
Action
• related to time
• related to place
• related to persons
Hypothesis generation
24. Surveillance: General Principle
Health Care System Public Health Authority
Data Information
Decision
Action
Feedback
Reporting
Evaluation
Analysis &
Interpretation
30. Surveillance: General Principle
Health Care System Public Health Authority
Data Information
Decision
Action
Feedback
Reporting
Evaluation
Analysis &
Interpretation
31. Surveillance: Function
Core function
• Detection
• Reporting
• Investigation & confirmation
• Analysis & interpretation
• Action / response
Support function
• Training
• Supervision
• Resources
• Standards / guidelines
