8. Public Health Surveillance - Copy.pptx

8) Public Health Surveillance
By: G/kiros G. (Bsc, MPH)
May, 2017

Session Objectives
After studying this lesson, you will be able to:
• Define public health surveillance
• List the essential activities of surveillance
• Describe sources of data and data systems commonly
used for public health surveillance
• Describe the principal methods of analyzing and
presenting surveillance data
2
7/28/2023 EPIDEMIOLOGY G/KIROS AMU

Public Health
Approach
Problem Response
Surveillance:
What
is the
problem?
Risk Factor
Identification:
What is the
cause?
Intervention
Evaluation:
What
works?
Implementation:
How do you
do it?
3

What is epidemiologic
surveillance?
 Derived from the French “sur” (over)
and “veiller” (to watch)
 is the “close and continuous observation of one
or more persons for the purpose of direction,
supervision, or control.”
4

Public Health Surveillance
It is an ongoing:
 systematic collection,
 analysis,
 interpretation and
 dissemination
of health related data for public action.
5

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EPIDEMIOLOGY G/KIROS AMU

Purposes and Uses of Public
Health Surveillance
 Assess public health status
 Define public health priorities
 Evaluate programs
 Stimulate research
 Detect sudden change in disease
occurrence and distribution.
7

Purposes and Uses of Public
Health Surveillance
8
To learn more about the natural history, clinical
spectrum and epidemiology of a disease.
To follow secular (long-term) trends of a disease
 To detect change in health care practices
 To assess the effectiveness of a preventive
intervention in a population

9

Population-based Vs Sentinel Surveillance
10
Population based;
Surveillance pertaining to the general
population defined by geographical boundaries
Sentinel:
It is a surveillance based on selected
population samples chosen to represent the
relevant experience of particular groups

Population-based Vs Sentinel Surveillance
11

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.
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Sentinel surveillance
Advantages
 relatively inexpensive
 provides a practical
alternative to population-
based surveillance
 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
7/28/2023 13

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.
 provider initiated reporting (routine reporting )
14

Advantages
Passive surveillance:
 covers a wide range of problems
 does not require special arrangement
 is relatively cheap
 covers a wider area
15

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
16

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
 public health system initiated reporting, or
(Public health official) initiated through resource
mobilization.
17

Advantages
The advantages of active surveillance
include:
 the collected data is complete and
accurate
 Information collected is timely.
 The required information is gathered
18

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
19

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.
20

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
21

Uses of Public Health Surveillance
 Estimate magnitude of the problem
 Determine geographic distribution of illness
 Portray the natural history of a disease
 Detect epidemics/define a problem
 Generate hypotheses, stimulate research
 Evaluate control measures
 Monitor changes in infectious agents
 Detect changes in health practices
 Facilitate planning
22

23

1. Data Collection and recording
Basic techniques of data collection include
the following:
 Record review
 Interviews
 Surveys using questionnaires, and
 Data Collection and recording
 Observation
7/28/2023 24

2. Data compilation and analysis
 In analyzing surveillance data, we first do
descriptive analysis by;
 time
 place
 person
 We usually use simple tabulations and
graphic techniques.
 Analysis of data must be made at every
level of the health delivery system.
7/28/2023 25

3. Interpretation
 After analyzing data, if the pattern of
disease is different from what we
expect, further investigation of the
disease is important.
 When we interpret data, we should be
cautious of considering Correct
numerator and denominator (population
increase or decrease).
7/28/2023 26

4. Dissemination of surveillance data
 Dissemination of surveillance data to
those who need to know is a critical
component of a surveillance system.
• The audience should include:
• Those who provide the reports (health
providers)
• The community who could be affected
• Those who participate in a program
planning and decision making.
7/28/2023 27

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.
 telephone-for special cases like emergency
situations.
 Written - in normal circumstances.
7/28/2023 28

Reporting and notification…
There are three periods of reporting:
1. Immediate reporting:
 A. For diseases considering presence of a single
 case to result to a suspicion for an epidemic.
 B. Suspected epidemic when a threshold is
crossed
2. On weekly basis:
 For epidemic prone diseases. eg Malaria,
meningitis
3. On monthly basis:
 For Routine surveillance eg Tuberculosis,
Leprosy, AIDS cases
7/28/2023 29

5. Link to public health action
 ‘Information for action’ means surveillance
should be functionally linked with public
health action.
 The action could be:
 Removal of common exposure (contaminated food),
 Lowering susceptibility through immunization
 Treating environment (a water supply).
 Education to change behavior ….. etc
 Usually the action is done on weak-link of
chain of transmission
7/28/2023 30

Selection of disease for surveillance
 All diseases may not be included in a
surveillance because of its costliness.
 The importance of a health event to be
included in surveillance system, it should
be assessed through certain criteria.
31

Criteria of inclusion in surveillance
32
1. The current impact of the health event
– Having high incidence/ prevalence
–Mortality (overall and age specific rates)
– Severity (case fatality rate, hospitalization)
eg Malaria, Pneumonia, Diarrheal dis., TB, HIV/AIDS
2. The disease should be of epidemic potential
(eg. Measles, cholera, meningitis)
3. Surveillance required internationally
(eg plague, yellow fever, cholera)

Criteria of inclusion in surveillance
4. Having available and effective
prevention and control interventions
(e.g. Schistosomiasis, Onchoserciasis)
5. Can easily be identified using simple
case definitions
6. Having intervention program already
found in the country
(eg EPI, IMCI)
33

List of Priority Diseases in Ethiopia
Epidemic-prone diseases
1. Cholera
2. Diarrhea with blood
(Shigellosis)
3. Measles
4. Meningitis
5. Plague
6. Viral hemorrhagic fever
7. Yellow fever
8. Typhoid fever
9. Relapsing fever
10. Epidemic typhus
11. Malaria
Diseases targeted for
eradication
12. Acute flaccid paralysis (Polio)
13. Dracunculiasis (Guinea worm)
14. Leprosy
15. Neonatal Tetanus(NNT)
Other diseases of public
health importance
16. Pneumonia in children
17. Diarrhea in children
18. New AIDS cases
19. Onchocerciasis
20. Sexually Transmitted Infections
21. Tuberculosis
22. Rabies
7/28/2023 EPIDEMIOLOGY G/KIROS AMU 34

Steps in Planning surveillance
G/kiros G. 35
1. Establish objectives
2. Develop case definitions
3. Determine data source or data collection
mechanisms
4. Develop data collection instruments
5. Field test methods
6. Develop and test analytic approach
7. Develop dissemination mechanism
8. Ensure use of analysis and interpretation

Case definition of diseases
 A case definition is a set of criteria used to
decide whether a person has a particular
disease.
It includes:
 Criteria: Signs and symptoms with or
without a laboratory test
 Classification of case definition is based on
Confirmed, Probable, Possible/ Suspect
36

37

38

39

Evaluation of Surveillance system
 To evaluate a surveillance system we
must assess each of the following:
1. Simplicity: refers to the ease of
operation of the system as a whole and
each of its components
2. Flexibility: the ability of a surveillance
system to accommodate changes in
operating conditions or information
needs
40

3. Acceptability: reflects the willingness of
individuals and organizations to
participate in a surveillance system.
4. Sensitivity: is the ability of a system to
detect the cases it is intended to detect.
 Sensitivity also refers to the system’s ability
to detect epidemics and other changes in
disease occurrence.
41

5. Predictive Value Positive: is the
proportion of reported cases which truly
are cases.
6. Representativeness: generalizability
7. Timeliness: the availability of data in
time for appropriate action.
8. Cost effective
42

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