DEFINITIONS OF SURVEILLANCE• “The continued watchfulness overthe distribution and trends ofincidence through the systematiccollection, consolidation, andevaluation of morbidity andmortality reports and otherrelevant data, together withdissemination to those who need toknow.”LANGMUIR, 1963
DEFINITIONS OF SURVEILLANCE• “Surveillance serves as thebrain and nervous systemfor programs to preventand control disease.”D.A. HENDERSON, 1976
DEFINITIONS OF SURVEILLANCE“Systematic ongoingcollection, collation and analysisof data and the timelydissemination of information tothose who need to know so thatthe actioncan be taken”WHO 2001
KEY ELEMENTS1. Collection of health data expressly foruse in health planning, disease control/prevention, and/or health promotion.2. Ongoing collection of data.3. Timely analysis.4. Easily understood.5. Dissemination of results.6. Action based on results.7. Periodic evaluation of the system.(Detels, 1989)
SURVEILLANCE SYSTEMEVALUATIONSensitivityTimelinessRepresentativenessPredictive valuepositiveAcceptabilityFlexibilitySimplicityCost/benefitDisseminationof resultsAppropriateaction taken
SURVEILLANCE SYSTEMEVALUATION• What proportion of“cases” areidentified?• Does the system givean accurate picture oftrends andmagnitudes?• Sensitivity
SURVEILLANCE SYSTEMEVALUATION• TimelinessIs information disseminatedrapidly enough to permit timelyaction based on the surveillancesystem?
SURVEILLANCE SYSTEMEVALUATION• Representativeness• Do reported casesdiffer from unreportedcases?
SURVEILLANCE SYSTEMEVALUATION• Positive predictivevalue• What proportion ofthose identifiedactually have thedisease or factor?
SURVEILLANCE SYSTEMEVALUATION• Acceptability• Does the system stimulatethe cooperation ofrespondents?• Does the processdiscourage participation?
SURVEILLANCE SYSTEMEVALUATION• Flexibility• Can changes be easily made inthe system to reflect changesin trends, magnitude andother relevant factors?
SURVEILLANCE SYSTEMEVALUATION• Simplicity• Can the system be simplifiedand still obtain the necessaryinformation?
SURVEILLANCE SYSTEMEVALUATION• Cost/benefit• Is the system worth the cost?• Can costs be reduced withoutsacrificing the essential qualityof the system ?
SURVEILLANCE SYSTEMEVALUATION• Dissemination ofresults• To decision-makers• To data collectors• To the general public
SURVEILLANCE SYSTEMEVALUATION• Appropriateaction taken• Are appropriate actionstaken in response to thesurveillance data?• Does surveillance lead toeffective intervention?
Comparison WithInternational Standards• Use of electronic notification system.• Category of reported cases.• Using of disease specific indicators.• Wide use of active surveillance.• Monitoring of diagnostic efforts.
Comparison With InternationalStandards• Monitoring circulation of organisms.• Awareness about the surveillance.• Giving frequent and relevant feedback.• Dissemination.• Risk Communication.• Evaluation of surveillance system.