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SURVEILLANCE AND NOTIFICATION OF
DISEASESGhaiath M.A. HusseinMBBS, MHSc. (Bioethics)
Outline of presentation
• What is surveillance?• What are the objectives of surveillance?• How to establish/run an effective surveillance
system?• Challenges to effective surveillance• Key messages
GhaiathSurveillance (JPFCM, Jan. 2010)
What is an epidemiological surveillance system?
• The systematic collection, analysis, interpretation, and dissemination of health data on an ongoing basis, to gain knowledge of the pattern of disease occurrence and potential in a community, in order to control and prevent disease in the community.
• Epidemiological surveillance is a process of watchfulness over health events which may occur in a population.
• A set of interconnected elements and activities that are usually established as an integral part of a health care system in order to monitor priority health events.
GhaiathSurveillance (JPFCM, Jan. 2010)
Surveillance: General principle
Health Care System Public Health Authority
Data Information
DecisionAction
Feedback
Reporting
EvaluationAnalysis & Interpretation
GhaiathSurveillance (JPFCM, Jan. 2010)
“Public Health Surveillance”
Ghaiath
Page 5 of 19
• Describes the scope (surveillance)
• Indicates the context in which the event occurs (public health)
Surveillance (JPFCM, Jan. 2010)
Task oriented approach to Communicable Disease Surveillance and Control
P P P P P P
II
C
World Health OrganisationRegional Offices + HQ
P = peripheral levelI = intermediate levelC = central Level
Detect TreatReport
AnalyseInvestigateReportRespondFeedback
Analysis and feedback SupportPolicy and targetsFunding
AnalyseInvestigateConfirmRespondPlan and FundFeedback
GhaiathSurveillance (JPFCM, Jan. 2010)
Elements of Surveillance
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• Collection
• Analysis
• Interpretation
• Dissemination
Surveillance (JPFCM, Jan. 2010)
Components of Public Health Practice
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Page 8 of 19
• Surveillance
• Research: epidemiological, behavioral, and laboratory
• Service (program evaluation)
• Training
Surveillance (JPFCM, Jan. 2010)
Purposes of Public Health Surveillance Data
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Page 9 of 19
• Assess status• Define position• Monitor and evaluate programs• Conduct research• Identify problems
Surveillance (JPFCM, Jan. 2010)
Comparing the number of confirmed dengue fever cases by International weeks
2006-2009
GhaiathSurveillance (JPFCM, Jan. 2010)
Confirmed dengue fever cases up to 31st International week2006-2009
GhaiathSurveillance (JPFCM, Jan. 2010)
• األولى (32000المرحلة - صفر ) محرم منزل• الثانية (130000المرحلة تاريخه ) حتى األول ربيع منزل
GhaiathSurveillance (JPFCM, Jan. 2010)
Steps in Planning Surveillance
1. Establish objectives2. Develop case definitions3. Develop data collection system4. Develop data collection instruments5. Field test methods
6. Develop data analysis approach
7. Determine dissemination mechanism
8. Determine evaluation method
Page 13 of 24
GhaiathSurveillance (JPFCM, Jan. 2010)
Which condition to surveillance?Page 14 of
24
Criteria for Determining High-Priority Events• Frequency
• Severity
• Direct and indirect costs
• Preventability
• Communicability• Public interest• Emerging issues
• Consensus process
GhaiathSurveillance (JPFCM, Jan. 2010)
Elements of a Case DefinitionPage 15 of
24
• Criteria for time, place, and person
• Clinical and laboratory diagnosis
• Epidemiological features of disease
• Degree of certainty regarding diagnosis
• High sensitivity and specificity
GhaiathSurveillance (JPFCM, Jan. 2010)
Data Collection
GhaiathSurveillance (JPFCM, Jan. 2010)
Determining Data Collection Systems
Page 17 of 24
• Methods of data collection
• Balance between system and its purpose
• Timeliness
• Type of condition
• Need for lab-based information
GhaiathSurveillance (JPFCM, Jan. 2010)
Types of Data Collection Systems
Page 18 of 24
• Vital records system
• Existing data sets
• Existing registries or surveys
GhaiathSurveillance (JPFCM, Jan. 2010)
Passive SystemsPage 19 of
24
• Simple
• Less burdensome
• Limited by variability
• May not be representative
• May fail to identify outbreaks• Portray trends
GhaiathSurveillance (JPFCM, Jan. 2010)
Active SystemsPage 20 of
24
• Validate representativeness
• Assure more complete reporting
• Can be used with specific investigations
• Can be used for brief periods
GhaiathSurveillance (JPFCM, Jan. 2010)
Uses of Limited Surveillance Systems
Page 21 of 24
• Resolve specific problems
• Identify all cases
• Use for logistic or economic reasons
GhaiathSurveillance (JPFCM, Jan. 2010)
GhaiathPage 22 of 27
Sentinel Surveillance
• Encompasses a wide range of activities focused on monitoring key health indicators in general or in special populations
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Sentinel refers to
• Key health events
• Clinics or other sites at which health events are monitored
• Reporters who report specific health events
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Sentinel Sites
• Hospitals
• Clinics
• Counties
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GhaiathPage 25 of 27
Role of Sentinel Sites
• Monitor conditions for which information is not otherwise available
• Monitor conditions in subgroups which are more vulnerable than general population
Surveillance (JPFCM, Jan. 2010)
Analysis and Interpretation of surveillance data
GhaiathSurveillance (JPFCM, Jan. 2010)
Considerations in Analysis of Surveillance Data
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Page 27 of 79
• Know inherent idiosyncrasies of data set
• Proceed from simplest to most complex
• Realize when inaccuracies in data preclude more sophisticated analyses
Surveillance (JPFCM, Jan. 2010)
Key Concepts that Determine Accuracy of Surveillance Data
Reliability:Is a particular condition reported consistently by different observers?
Validity:Does the particular condition as reported reflect the true condition as it occurs?
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Page 28 of 79
Surveillance (JPFCM, Jan. 2010)
Basic Epidemiological Parameters
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• Time
• Place
• Person
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Data Analysis by Time
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Page 30 of 79
• Compare number of case reports received during a specific interval
• Compare number of cases for a current time period with number reported during same interval during previous time period
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Data Analysis by Place
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• Where exposure occurred, not where it’s reported from
• Allows prevention resources to be targeted effectively
• Use of computers and spatial mapping software allows for sophisticated analysis
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Data Analysis by Person
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Possible variables:agegenderrace or ethnicitymarital statusoccupationlevels of income and education
Surveillance (JPFCM, Jan. 2010)
Interactions Among Time, Place, and Person
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Page 38 of 79
• Interactions can obscure patterns of disease and injury
• Syphilis in the 1980s
Surveillance (JPFCM, Jan. 2010)
Why Interpret and Disseminate Information?
Page 39 of 24
• Help decision makers understand the implications of information
• Facilitate consequent implementation of public health action
GhaiathSurveillance (JPFCM, Jan. 2010)
Interpretation of InformationPage 40 of
24
• Present information clearly
• Know your audience
GhaiathSurveillance (JPFCM, Jan. 2010)
Considerations for Dissemination
Page 41 of 24
• Balance access with privacy constraints
• Provide analyses and recommendations
• Use clear and concise materials
• Use communications media
• Use current AV technology
GhaiathSurveillance (JPFCM, Jan. 2010)
Steps in Dissemination
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1. Use visual displays to convey structure of data and analyses
2. Transform data mathematically to simplify distribution
3. Investigate influence of outliers
4. Examine residuals
Surveillance (JPFCM, Jan. 2010)
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Purpose of Graphics
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Page 47 of 79
• To visually display measured quantities• To allow researchers to mesh presentation and
analysis• To organize, summarize, and display
information clearly and effectively
Surveillance (JPFCM, Jan. 2010)
Tables
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Page 48 of 79
• Arrange data in rows and columns• Demonstrate data patterns and relationships
among variables• Serve as a source of information for other
types of data graphics
Surveillance (JPFCM, Jan. 2010)
Guidelines for Developing a Table
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Page 49 of 79
• Describe what, when, where in the title• Label rows and columns clearly• Provide units of measure• Provide row and column totals• Define abbreviations and symbols• Note data exclusions• References Source• Should stand alone
Surveillance (JPFCM, Jan. 2010)
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البعوضوالعدد ليرقات المستكشفة المواقع بعدد بياناإليجابي
وفبراير يناير شهري خالل المكرمة م2009بمكة
اليرقات األخرى
األيدس يرقات عددإيجبتاي ألماكن ا
اإليجابية لليرقــــات
المواقـــــع
المستكشفة
األسبوع الوبائي
الشهـــــــط1طر
2ط1ط
2 4ط + 3ط 2ط + 1ط
357 254 547 110 25 770 1
يناير
567 133 421 87 43 926 2
510 168 296 193 45 841 3
216 95 530 264 40 819 4
302 110 610 329 54 956 5
145 24 608 128 55 884 6
فبراير646 312 599 305 13 1038 7
331 231 456 163 83 876 8
275 151 328 204 57 1118 9
Graphs
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Page 52 of 79
• Visually display quantitative information• Provide system of coordinates• Assist reader to visualize patterns and
trends
Surveillance (JPFCM, Jan. 2010)
Guidelines in Developing Graphs
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Page 53 of 79
• Label title, source, axes, scales, legend• Minimize the number of coordinate lines• Portray frequency on the vertical scale, starting
with zero• Portray method of classification on the horizontal
scale• Indicate units of measure• Define abbreviations and symbols• Note data exclusions
Surveillance (JPFCM, Jan. 2010)
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Maps
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Page 60 of 79
• Graphically represent data using location and geographic coordinates
• Provide a clear, concise, and quick method for grasping data
Surveillance (JPFCM, Jan. 2010)
• األولى (32000المرحلة - صفر ) محرم منزل• الثانية (130000المرحلة تاريخه ) حتى األول ربيع منزل
Limitations in Data
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Page 62 of 79
• Under-reporting
• Unrepresentativeness
• Inconsistent case definitions
Surveillance (JPFCM, Jan. 2010)
Considerations for Interpreting
Data
• Has nature of reporting changed?
• Have new providers or geographic areas entered the system?
• Has case definition changed?
• Has new intervention been introduced?
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Page 63 of 79
Surveillance (JPFCM, Jan. 2010)
Interpretive Uses for Surveillance Data
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Page 64 of 79
• Monitoring trends • Identifying epidemics• Identifying syndrome• Evaluating public policy• Projecting future needs
Surveillance (JPFCM, Jan. 2010)
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Limitations of Reporting Systems
• Under reporting• Incomplete reporting
* If consistent surveillance methods are used, data will describe trends despite under reporting
Surveillance (JPFCM, Jan. 2010)
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Factors Contributing to Incomplete Reporting
• Concealment due to social stigma• Lack of awareness of requirements• Inadequate knowledge of case definitions• Changes in procedures• Variations in diagnosis skills• Low priority
Surveillance (JPFCM, Jan. 2010)
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Strengths of Reporting System
• Quick information• Detect changes in patterns• Detection of outbreaks• Availability of information from all
jurisdictions• Basis for prevention recommendations
Surveillance (JPFCM, Jan. 2010)
Discussion… (Qs & As)
GhaiathSurveillance (JPFCM, Jan. 2010)
references
• FETP series lectures on epidemiology
GhaiathSurveillance (JPFCM, Jan. 2010)