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1. Public Health Surveillance
T.T 1

2. Outline
Surveillance
 Definition
 Purpose
 Types
 Sources of data
 Features of a good surveillance system
 Limitation
 IDSR
T.T 2

3.  Surveillance is a systematic collection,
analysis, interpretation and dissemination of
relevant health data for monitoring the
occurrence and trends of disease in human
population on an ongoing basis.
 WHO defines surveillance as the continuous
(ongoing) analysis of the factors that
determine the occurrence and distribution
of diseases and other health related events
through a systematic collection of data.
 Surveillance data provides information for
action.
T.T 3
Definition
“Information for Action

4. Definition…
 Surveillance systems are often
considered information loops or cycles
involving health care providers, public
health agencies, and the public.
T.T 4
Public Health Surveillance is the continuous systematic collection, analysis,
interpretation, and dissemination of health data for the purpose of
describing and monitoring health events, setting priorities, and assisting
the planning, implementation, and evaluation of public health
interventions and programs.
Sensitivity (ability to detect cases), simplicity, dynamicity (ability to
accommodate changes) and timeliness are the most important desirable
characteristics of a surveillance system.

5. Uses of surveillance system
 Determine magnitude of problems
 Priority setting and planning
 Monitoring health events:-
 Detect sudden changes in disease occurrence
 To follow secular trends of diseases
 To identify changes in agents and host factors
 To detect change in health care practice
 Monitoring and evaluation of health programs
 Facilitates epidemiological and laboratory
researches
5
T.T

6. Criteria for selection of disease for
surveillance
 Frequency(magnitude )
A, Morbidity rates
 Incidence
 Prevalence
B, Mortality rates
 Severity
 Case fatality ratio
 Hospitalization rate
 Disability rate
 Cost
 Preventability
 Communicability(Epidem
ic potential)
 Public Interest
 Frequency( magnitude )
 Severity
 Feasibility for control
 Monitor & Evaluation
of control program
 Resource availability
 International focus
area
T.T 6

7. There are three major types of surveillance:
 Passive Surveillance
 Active Surveillance
 Sentinel Surveillance
T.T 7
Types of surveillance

8. Passive surveillance
 Passive surveillance may be defined as a
mechanism for routine survey based on passive
case detection and on the routine recording and
reporting system.
 The information provider comes to the health
institutions for help, be it medical or other.
 It involves collection of data as part of routine
provision of health services.
T.T 8

9. Advantages
Passive surveillance:-
 Covers a wide range of problems
 Does not require special arrangement
 Is relatively cheap
 Covers a wider area
T.T 9

10. Disadvantages
 The information generated is to a large extent
unreliable, incomplete and inaccurate
 Most of the time, data from passive surveillance is
not available on time
 You may not get the kind of information you
desire
 It lacks representativeness as it is mainly from
health institutions
 There is no feed back system
 The Denominator is unknown
T.T 10

11. Active surveillance
A method of data collection usually on a
specific disease, for relatively limited
period of time.
It involves collection of data through:
 House-to-house surveys or
 Mobilizing communities to some central
point where data can be collected.
 Example:- Investigation of out-breaks
T.T 11

12. Advantages
The advantages of active surveillance include:
 The collected data is complete and accurate
 Information collected is timely.
 The required information is gathered/desired
T.T 12

13. Disadvantages
 It requires good organization,
 it is expensive
 Requires skilled human power
 It is for short period of time
 It is directed towards specific disease
conditions
T.T 13

14. Active surveillance cont…
Conditions in which active surveillance is
appropriate
 For periodic evaluation of an ongoing program
 For programs with limited time of operation such as
eradication program.
 In unusual situations such as
 New disease discovery
 New mode of transmission
 When a high-risk season/year is recognized.
 When a disease is found to affect a new subgroup
of the population.
 When a previously eradicated disease reappears.
T.T 14

15. Sentinel Surveillance
Sentinel surveillance uses a pre-arranged sample
of reporting sources to report all cases of one or
more conditions. This is carried out by:
 Selecting sample sources most likely to see cases
of the specified condition.
 Identifying institutions that serve the population
subgroups and that can obtain data regarding the
condition of interest.
 Sentinel surveillance provides a practical
alternative to population-based surveillance, in
developing countries.
 Method to detect cases missed by the routine
notification system
T.T 15

16. Advantages
 Relatively inexpensive
 Provides a practical alternative to population-based
surveillance (EHDS )
 Can make productive use of data collected for other
purposes
Disadvantages
 The selected population may not be representative of
the whole population
 Use of secondary data may lead to data of lesser
quality and timeliness
T.T 16

17. Activities of Surveillance
T.T 17

18. Data Collection and recording
Basic techniques of data collection include
the following:
 Record review
 Interviews
 Surveys using questionnaires, and
 Data Collection and recording
 Observation.
T.T 18

19. Sources of data for surveillance
The major sources summarized by the WHO in 1968 are
as follows:
 Mortality registration
 Morbidity registration
 Epidemic reporting
 Reports of laboratory utilization (Including lab test
results)
 Reports of individual case investigations
 Reports of epidemic field investigations
 Special surveys
 Information on animal reservoir and vector distribution
 Report of biologics and drug utilization
 Knowledge of the population and environment
T.T 19

20. Data compilation, analysis and
interpretation
 The data should be collected at each level of the
health care delivery system. Each level makes sure
that the quality of information collected should be
accurate, complete, reliable, and submitted on time.
 As with all descriptive epidemiological data,
surveillance data is first analyzed in terms of time,
place and person using simple tabular and graphic
techniques to analyze and display these data.
 Analysis of data must be made at every level of the
health delivery system.
 Analysis at the health facility level helps to recognize
problems timely and to take appropriate action
immediately.
T.T 20

21. Data analysis cont…
Proper analysis of surveillance data includes
determination of both numbers and rates.
The interpretation: Is the change a true change?
Apparent/real changes can occur as a result of:
 Change in the population size,
 Improvement in the diagnostic capability,
 Improved reporting,
 Improved health service coverage, etc.
T.T 21

22. Reporting and notification
Reporting formats must be clear and easy to use.
Any report must be clear and answer questions
like what, where, when, to whom, for what and
why.
Types of reports
 Oral: - passing information verbally and the
sender must check that the message is correctly
understood by the receiver.
 Radio or telephone-for special cases like
emergency situations.
 Written - in normal circumstances.
T.T 22

23. Dissemination of information
To ensure motivation and active
involvement there must be:-
 Preparation of regular weekly, monthly,
quarterly and annual reports
 Regular feedback from higher levels
 Publication of newsletters
T.T 23

24. Features of a good surveillance
system
 Using a combination of both active and
passive surveillance techniques.
 Timely notification.
 Timely and comprehensive action taken
in response to notification.
 Availability of a strong laboratory service
for accurate diagnoses of cases.
T.T 24

25. Limitation of surveillance
 Under reporting
 Non representativeness
 Bias
 Lack of timeliness
 Inconsistencies of case definitions
T.T 25

26. Integrated Disease surveillance and
response (IDSR)
 An approach adapted to strengthen
national disease surveillance systems
by coordinating and
streamlining(reforming) all
surveillance activities and ensuring
timely provision of surveillance data
to all disease prevention and control
programmes.
T.T 26

27. IDSR….cont
A/Disease specific B/ IDSR
surveillance
T.T 27

28. IDSR…cont
 Integrated disease surveillance system:
 Focus on woreda level
 Coordinate and streamline all surveillance
activities combining available resource from a
single focal point at woreda level
 Facilitates collaboration b/n surveillance focal
points at different levels
T.T 28

29. Objective of IDSR
 To provide timely evidence on which to
base decisions and public health
interventions for effective control of
communicable diseases.
 Strengthen capacity of Woreda
 Integrate multiple surveillance system to
use scarce resources effectively and
efficiently
T.T 29

30. Objective of IDRS…cont
 Improve use of information for decision
making
 Improve laboratory capacity
 Emphasis community and health worker
participation
 Improve information flow
T.T 30

31. T.T 31
Federal MOH
Central Referral
Hospitals
Regional Health Bureau
Regional hospitals
Regional
laboratories
Zonal Health Department
District Hosp
PHC facilities
Woreda Health Office
District hospital
PHC facilities
The
community
WHO
Data collection, analysis,
Action and reporting
Supervision and feedback

32. Which diseases are to be included?
 About 21 diseases are included because
of either:
o Top cause of morbidity and mortality
(malaria, TB, HIV, )
o Have epidemic potential (cholera, yf)
o Surveillance required internationally
(plague, Yf, Cholera)
o Availability of effective control
T.T 32

33. T.T 33
List of Priority Diseases in Ethiopia
Epidemic-Prone Diseases
1. Cholera
2. Diarrhoea with blood (Shigella)
3. Measles
4. Meningitis
5. Plague
6. Viral hemorrhagic fevers***
7. Yellow Fever
8. Typhoid Fever
9. Relapsing Fever
10. Epidemic Typhus
11. Malaria
Diseases Targeted for Eradication and Elimination
1. Acute flaccid paralysis (AFP)/polio
2. Dracunculiasis (Guinea Worm)
3. Leprosy
4. Neonatal tetanus
Other Diseases of Public Health Importance
1. Pneumonia in children less than 5 years of age
2. Diarrhea in children less than 5 years of age
3. New AIDS cases
4. Onchocerciasis
5. Sexually transmitted infections (STIs)
6. Tuberculosis

34. T.T 34
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