Surveillance and Notification of Diseases

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.

Surveillance: General principle

Health Care System Public Health Authority

Data Information

DecisionAction

Feedback

Reporting

EvaluationAnalysis & Interpretation

“Public Health Surveillance”

Ghaiath

• 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

World Health OrganisationRegional Offices + HQ

P = peripheral levelI = intermediate levelC = central Level

Detect TreatReport

AnalyseInvestigateReportRespondFeedback

Analysis and feedback SupportPolicy and targetsFunding

AnalyseInvestigateConfirmRespondPlan and FundFeedback

Elements of Surveillance

Ghaiath

• Collection

• Analysis

• Interpretation

• Dissemination

Components of Public Health Practice

Ghaiath

• Surveillance

• Research: epidemiological, behavioral, and laboratory

• Service (program evaluation)

• Training

Purposes of Public Health Surveillance Data

Ghaiath

• Assess status• Define position• Monitor and evaluate programs• Conduct research• Identify problems

Comparing the number of confirmed dengue fever cases by International weeks

2006-2009

Confirmed dengue fever cases up to 31st International week2006-2009

• األولى (32000المرحلة - صفر ) محرم منزل• الثانية (130000المرحلة تاريخه ) حتى األول ربيع منزل

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

Which condition to surveillance?Page 14 of

Criteria for Determining High-Priority Events• Frequency

• Severity

• Direct and indirect costs

• Preventability

• Communicability• Public interest• Emerging issues

• Consensus process

Elements of a Case DefinitionPage 15 of

• Criteria for time, place, and person

• Clinical and laboratory diagnosis

• Epidemiological features of disease

• Degree of certainty regarding diagnosis

• High sensitivity and specificity

Data Collection

Determining Data Collection Systems

• Methods of data collection

• Balance between system and its purpose

• Timeliness

• Type of condition

• Need for lab-based information

Types of Data Collection Systems

• Vital records system

• Existing data sets

• Existing registries or surveys

Passive SystemsPage 19 of

• Simple

• Less burdensome

• Limited by variability

• May not be representative

• May fail to identify outbreaks• Portray trends

Active SystemsPage 20 of

• Validate representativeness

• Assure more complete reporting

• Can be used with specific investigations

• Can be used for brief periods

Uses of Limited Surveillance Systems

• Resolve specific problems

• Identify all cases

• Use for logistic or economic reasons

GhaiathPage 22 of 27

Sentinel Surveillance

• Encompasses a wide range of activities focused on monitoring key health indicators in general or in special populations

Sentinel refers to

• Key health events

• Clinics or other sites at which health events are monitored

• Reporters who report specific health events

Sentinel Sites

• Hospitals

• Clinics

• Counties

Role of Sentinel Sites

• Monitor conditions for which information is not otherwise available

• Monitor conditions in subgroups which are more vulnerable than general population

Analysis and Interpretation of surveillance data

Considerations in Analysis of Surveillance Data

Ghaiath

• Know inherent idiosyncrasies of data set

• Proceed from simplest to most complex

• Realize when inaccuracies in data preclude more sophisticated analyses

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?

Ghaiath

Basic Epidemiological Parameters

Ghaiath

• Time

• Place

• Person

Data Analysis by Time

Ghaiath

• 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

GhaiathPage 31 of 79 Surveillance (JPFCM, Jan. 2010)

Data Analysis by Place

Ghaiath

• 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

Data Analysis by Person

Ghaiath

Possible variables:agegenderrace or ethnicitymarital statusoccupationlevels of income and education

Interactions Among Time, Place, and Person

Ghaiath

• Interactions can obscure patterns of disease and injury

• Syphilis in the 1980s

Why Interpret and Disseminate Information?

• Help decision makers understand the implications of information

• Facilitate consequent implementation of public health action

Interpretation of InformationPage 40 of

• Present information clearly

• Know your audience

Considerations for Dissemination

• Balance access with privacy constraints

• Provide analyses and recommendations

• Use clear and concise materials

• Use communications media

• Use current AV technology

Steps in Dissemination

Ghaiath

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

Purpose of Graphics

Ghaiath

• To visually display measured quantities• To allow researchers to mesh presentation and

analysis• To organize, summarize, and display

information clearly and effectively

Tables

Ghaiath

• 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

Guidelines for Developing a Table

Ghaiath

• 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

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

Ghaiath

• Visually display quantitative information• Provide system of coordinates• Assist reader to visualize patterns and

trends

Guidelines in Developing Graphs

Ghaiath

• 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

Ghaiath

• Graphically represent data using location and geographic coordinates

• Provide a clear, concise, and quick method for grasping data

• األولى (32000المرحلة - صفر ) محرم منزل• الثانية (130000المرحلة تاريخه ) حتى األول ربيع منزل

Limitations in Data

Ghaiath

• Under-reporting

• Unrepresentativeness

• Inconsistent case definitions

Considerations for Interpreting

• Has nature of reporting changed?

• Have new providers or geographic areas entered the system?

• Has case definition changed?

• Has new intervention been introduced?

Ghaiath

Interpretive Uses for Surveillance Data

Ghaiath

• Monitoring trends • Identifying epidemics• Identifying syndrome• Evaluating public policy• Projecting future needs

Limitations of Reporting Systems

• Under reporting• Incomplete reporting

* If consistent surveillance methods are used, data will describe trends despite under reporting

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

Strengths of Reporting System

• Quick information• Detect changes in patterns• Detection of outbreaks• Availability of information from all

jurisdictions• Basis for prevention recommendations

Discussion… (Qs & As)

references

• FETP series lectures on epidemiology

Surveillance and Notification of Diseases

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