Infectious Disease Epidemiology, Module I Introduction

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  • Infectious Disease Epidemiology, Module IIntroduction

    ANN JOLLY

  • IntroductionRound tableYour expectations of this dayYour career goalsKnowledge baseWhy is infectious disease epidemiology important?

    ANN JOLLY

  • General goalsUnderstand the infectious disease processIdentify transmission routes, modes, media and reservoirsUnderstand public health law Understand infectious disease surveillanceUnderstand the process of outbreak investigation

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  • What causes disease?AgentHostEnvironmentBacteriaVirusesFungiParasitesPrions

    HousingFoodWater qualityAir qualityAgeGenderEthnic groupLifestyleSocioeconomic

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  • ExposureInfectionDisease, symptomatic/asymptomatic

    CarrierConvalescentSequelaeInfectious disease process

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  • What determines infection?

    (other than exposure)The deposition, colonisation and multiplication of an organism in a host,Usually accompanied by an immune responseMay occur with or without clinical illness

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  • Predictors of infection

    AGENTHOSTENVIRONMENTImmunityRaceAgeGenderSocioeconomicLiving ConditionsSocialClimateDoseGeneticsHardinessCommunicability

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  • Infectious disease process - Source ReservoirshumaninsectanimalMediumair bornewater bornefood borne blood bornegenital

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  • Infectious disease process- Transmission RoutedirectOral, oral/faecalsexualrespiratory - droplets or droplet nuclei 1-5mparenteralcongenitalindirectvectorvehicle

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  • Infectious disease process -Infection & IncubationInfectiondoseinfectivityhardinessrate of replicationIncubationinfectiousnessimmune responseintervention

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  • Infectious disease process- DiseaseDiseasesigns, symptomsasymptomatic infectiousOutcome/Prognosismorbiditymortalitysequelaerecoveryinfectious (chronic carrier)

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  • DiagnosisClinicalbased on signs, symptomsLaboratory confirmedmicrobiologydetectionisolationserologyparasitologyvirus

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  • Diagnostic processPatient presentsdue to symptomscase - findingscreeningactive investigation of contacts

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  • Laboratory diagnosisLab tests orderedMethod of collection, site, volumeRight tests orderedcorrect organismsantimicrobial sensitivitySent to the right placeIn the right mediaTransport conditionsTimeTemperature

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  • Laboratory diagnosis, (cont.)Routine identification of organisms causing diarrhoeaC & S shigellaesalmonellaeyersiniaaeromonas campylobacterIn children < 5 in the summerVertoxigenic E. coli

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  • Laboratory diagnosis, (cont.)If food-borne is suspected and written on the requisitionstaph aureusbacillus cereusclostridium perfringens

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  • Interpretation of tests, if positiveTest sensitivity% of people accurately diagnosed as ill of all people testedNormal flora?N. meningitidisStreptococcus pyogenesCarrier stateContamination during collectionLab. ErrorMultiple infections

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  • Interpretation of tests, if negativePrior antibiotic therapyProblems incollectiontimingsitestoragetransportmediaFailure to incubate long enough

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  • Summary

    Infectious disease processreservoir - transmission - disease/deathDeterminants of infectionagent, host, environment interaction

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  • Next Steps Future applieddisease in populationssurveillanceoutbreaks

    ANN JOLLY

    Emphasize multicausation Tuberculosis good e.g..If you are well off and live in good housing, unlikely to be exposed, to get itIf you do, likely to be able to get well. If poor and exposed unlikely to overcome it, become infectious and expose more family and friends. So you have to have the agent, low immunity and poor living conditions etc. for the bug to flourish

    Bicycle accident in childAgent = speed, child not wearing a helmetEnvironment , riding on a busy street

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