PHSf 318 EPIDEMIOLOGYf FORf COMMUNITYf HEALTH
MODULE 1 f INTRODUCTION TO EPIDEMIOLOGY
f f
Unitf1
Introductionf tofEpidemiologyfUni
tf 2 Typesf offEpidemiologicalf Studies
Unitf3 Basicf Measurementsf inf Epidemiology
UNIT 1 f INTRODUCTION TO EPIDEMIOLOGY
f f
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 MainfContent
3.1 Definitionf offEpidemiology
3.2 Significancef offEpidemiology
3.3 Usesf off Epidemiology
4.0 Conclusion
5.0 Summary
6.0 Tutor-Markedf Assignment
7.0 References/Furtherf Reading
1.0 INTRODUCTION
This isfff PHSf318:fffEpidemiology forfff Community Health. Having
successfullyfgonefthroughfCHSf241:fIntroductionftofBiostatistics,fafsureffound
ationfhasfbeenflaidftof preparef youf forf epidemiologicalf studies.fMostf epide
miologicalf researchf informsf thef planningf andf implementationfoff health-
relatedf policyf andf thisf policyf hasf af fundamentalf impactf onf thefwayf healthf p
ractitionersf deliverf care.f Manyf aref unawaref off thef impactfthatf epidemiolo
gyf hasf onf theirf workingf practice.f Thisf unitf thereforefhopesf tof unfoldf thef con
ceptf off epidemiologyf andf itsf placef inf nursingf andfhealthfservicef delivery.
2.0 OBJECTIVES
Atfthefendfoffthisfunit,f youfshouldf befablefto:fde
finef epidemiology
describef thef usesf off epidemiology
determinef itsf relevancef tofcommunityfhealthf practitioners.
11
,PHSf 318 EPIDEMIOLOGYf FORf COMMUNITYf HEALTH
3.0 MAIN CONTENT
f
3.1 Definition of Epidemiology
f f
Epidemiologyfisfthefstudyfoffthefdistributionfandfdeterminantsfoffhealth-
frelatedf eventsf inf specifiedf populationsf andf thef applicationf off thisf studyftof
thefcontrolfoffhealthfproblemsf(J.fMfLast,f1995).fEpidemiologyfwasfcoinedf fro
mf af Geekf wordf meaningf „thef sciencef off people‟.f Historically,fthefimpactfoff
epidemiologyfonfthefhealthfoffnationsfhasfbeenf long-fstandingfandffar-
reaching.fItsforiginfcanflooselyfbeftracedftoftheftimefoffHippocratesf(460-
377fBC)fwho,f asfafphysician,f attemptedftofinvestigatefthefoccurrencefoffdisea
sefonfafrationalfbasisf (Valanisf 1992).f Inf Britain,fitsfformativefrootsfcanfbeftra
cedfbackftofisolatedfstudiesfoff specificfdiseasesfinfthefearlyf19thfcentury.fThes
efinvestigationsfculminatedfinfthefcelebratedfstudyfbyfJohnfSnowf(referredf tof
asf thef fatherf offepidemiology)f who,faroundfthef1850s,f observedf patternsfof
fincidencef offafcholerafoutbreakfinfcentralfLondon.fAsfafresultfoffhisfrecordingf
offthefincidencefoffcholerafandf mortalityfinfthefarea,f Snowfwasf ableftofisolate
fthefcausefoffthefcholerafepidemicfwhichfwasfattributedftofafcommunal fwater-
pumpfinfBroadfStreet,fSoho.fAfterfremovingf thef pumpf handle,fSnowfobserv
edfthatfnewfcasesfoffcholerafinfthefareafceasedfandfthefepidemicf declined.
Althoughfdismissedfbyfmostfscientistsfoff thef time,f thisf findingf andfothersf r
elatedf tof diseasef andf thef environmentf hadf af profoundf effectf onfthefformati
onfoffthefpublicfhealthfmovementfandfthefearlyfPublicfHealthfActsfoff1848f and
f1875.
Originally,ftheftermfepidemiologyfmeantfthefstudyfoffepidemics,fbutftheftechn
iquesf havef longf beenf improvedf upon.f Itf isf anf appliedf disciplinef andfafbasicfs
ciencefoffpreventivefandfsocialfmedicinef(notftheoretically)fandfmethodsfarefe
ssentiallyfobservational.fThus,fthefmodernfdefinitionfoffepidemiologyf accom
modatesf threef importantf elementsfffnamely:finclusionfoffallfdiseases,fpopulat
ions,f andfecologicalf approach.f Pleasefnotefthefthreefcomponentsf(3Ds)fcom
monftofthefdefinitionf offepidemiology:f diseaseffrequency,f distributionf andfd
eterminants.
Thef majorf questionsf thatf aref usuallyf askedf inf epidemiologyf are:f whof arefthe
fgroupfoffpersonf(s)faffectedfbyfthefdisease, fwherefhasfthefincidencefoccurred? f
Andfwhenf(time)fdidfitfoccur?
2
,PHSf 318 EPIDEMIOLOGYf FORf COMMUNITYf HEALTH
SELF-ASSESSMENTf EXERCISE
Highlightf thef3fimportantf componentf off epidemiology
3.2 Why Do We Study the 3 Components in Epidemiology?
f f f f f f f f
Theffollowingfreasonsfhavefbeenfadducedfforfstudyingfthesefthreef‘Ds’:fdisea
seffrequency,fdistributionfandf determinantsf off diseasesf infhumanf popul
ation:
forfplanningf andf evaluationf offhealthf care
forfidentificationf offthefdeterminantsf offdiseasesff
orf evaluationf offmethodf offcontrollingf disease
forf observationf off thef naturalf historyf off af disease-
makingf upf offdiagnosisf andfprognosis
forfclassificationf offafdisease.
3.3 Uses of Epidemiology
f f
Youfmayfrecallffromfthefactivityfabovefthatfthefstudyfoff diseasefdistributionfa
ndfcausationfisf centralf tof epidemiology.f Thef broadfgroupingf offthefusesfoc
cursf inftheffollowingf areasf namely:
i. understandingf thef causationf off thef diseasef andf thef developmentfoff
hypothesisf andftheirftesting
ii. understandingf offgeographicalf orflocalf patternsf offthef diseases
iii. administrationf (i.e.)f thef planningf offhealthf activitiesf andf directionfof
fprogrammef tofrelevantf sub-groupf identifiedf tof befatfrisk.
However,f epidemiologyf isfusedfforftheffollowing:
tof analysef thef respectivef rolef off agent,f hostf andf thef environmentfinft
hefdevelopmentf andfthefnaturalf historyfoffdisease
tof analysef thef occurrencef andf distributionf offdiseasef accordingf tofch
aracteristicsf suchf asfage,f sex,frace,f occupationf andfheredity
tofstudy,f outlinef andfdefinef problemsf offhealthf andf diseasef byfthefanal
ysisf offincidence,f prevalencef andf mortality
tofhelpf completef thefclinicalf featuref andf naturalf historyfoffdiseasefbyfgr
oupf analysis
tof estimatef anf individual‟sf riskf off developingf af diseasef andf hisfsurvi
valf chances
tof searchfforf factorsf relatedf tof healthf andf diseasef throughf thefobser
vationf off groupf customf andfhabits
forfplanningfandfallocationf offresources
3
, PHSf 318 EPIDEMIOLOGYf FORf COMMUNITYf HEALTH
tof evaluatef thef needf forf andf thef effectivenessf off healthf servicefthroug
hf fieldfstudies.
4.0 CONCLUSION
Thefscopefoffepidemiology,fitsfrangef off designsf andf impactf onfhealthcareff
ormationfandfreformationf hasf beenf immense.f Manyfhealthcarefrelatedf strat
egiesf andf policiesf thatf havef influencedfcommunityfhealthfpracticefoverfthef
pastfcenturyforfsofhavef beenfestablishedfasfafconsequencef off epidemiologica
lf study.f Itsf usesf alsofhavefcontributedftofincreasingfknowledgefonfhealthcar
e.fTheffactfthatfepidemiologyfisfseenftof bef morefholistic,f lessfstructured,f foc
usingf notfjustfonfindividuals,fbutfonfcommunities,fandflooksftowardsfpreventi
vefstrategies,finsteadfoffcurativefones,fmakesfitfanfidealfstrategyftofbefincorpor
atedf intofday-to-dayflifefexperiencesf andf professionalf practice.
5.0 SUMMARY
Thisfunitfhasftouchedfonfepidemiology,frationalefforfstudyingfthef3fDsfnamely
:fthefdiseaseffrequency,fdistributionf andfdeterminantsf asfwellf asfthefusesf forf t
hefoverallf improvementf offourfhealthcare.
6.0 TUTOR-MARKED ASSIGNMENT f
Discussf fivef (5)fimportancef offepidemiology.
7.0 REFERENCES/FURTHER READING f
Last,fJ.f(1994).fThefUsesfoffEpidemiology.fIn:fAshton,fJ.f(Ed.).fThefEpidemiol
ogicalfImagination.f Buckingham,f Openf UniversityfPress.
Lucasf &fGillesf (2003).f ShortfTextbookf offPublicfHealthf Medicinef forfthefT
ropics.f London:f Oxfordf Universityf Press.
Park,f K.f(2000).f Textbookf off Preventivef andf Socialf Medicine.f India:f M/sfBanarsi
dasf Bhanotf Publishers.
4
MODULE 1 f INTRODUCTION TO EPIDEMIOLOGY
f f
Unitf1
Introductionf tofEpidemiologyfUni
tf 2 Typesf offEpidemiologicalf Studies
Unitf3 Basicf Measurementsf inf Epidemiology
UNIT 1 f INTRODUCTION TO EPIDEMIOLOGY
f f
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 MainfContent
3.1 Definitionf offEpidemiology
3.2 Significancef offEpidemiology
3.3 Usesf off Epidemiology
4.0 Conclusion
5.0 Summary
6.0 Tutor-Markedf Assignment
7.0 References/Furtherf Reading
1.0 INTRODUCTION
This isfff PHSf318:fffEpidemiology forfff Community Health. Having
successfullyfgonefthroughfCHSf241:fIntroductionftofBiostatistics,fafsureffound
ationfhasfbeenflaidftof preparef youf forf epidemiologicalf studies.fMostf epide
miologicalf researchf informsf thef planningf andf implementationfoff health-
relatedf policyf andf thisf policyf hasf af fundamentalf impactf onf thefwayf healthf p
ractitionersf deliverf care.f Manyf aref unawaref off thef impactfthatf epidemiolo
gyf hasf onf theirf workingf practice.f Thisf unitf thereforefhopesf tof unfoldf thef con
ceptf off epidemiologyf andf itsf placef inf nursingf andfhealthfservicef delivery.
2.0 OBJECTIVES
Atfthefendfoffthisfunit,f youfshouldf befablefto:fde
finef epidemiology
describef thef usesf off epidemiology
determinef itsf relevancef tofcommunityfhealthf practitioners.
11
,PHSf 318 EPIDEMIOLOGYf FORf COMMUNITYf HEALTH
3.0 MAIN CONTENT
f
3.1 Definition of Epidemiology
f f
Epidemiologyfisfthefstudyfoffthefdistributionfandfdeterminantsfoffhealth-
frelatedf eventsf inf specifiedf populationsf andf thef applicationf off thisf studyftof
thefcontrolfoffhealthfproblemsf(J.fMfLast,f1995).fEpidemiologyfwasfcoinedf fro
mf af Geekf wordf meaningf „thef sciencef off people‟.f Historically,fthefimpactfoff
epidemiologyfonfthefhealthfoffnationsfhasfbeenf long-fstandingfandffar-
reaching.fItsforiginfcanflooselyfbeftracedftoftheftimefoffHippocratesf(460-
377fBC)fwho,f asfafphysician,f attemptedftofinvestigatefthefoccurrencefoffdisea
sefonfafrationalfbasisf (Valanisf 1992).f Inf Britain,fitsfformativefrootsfcanfbeftra
cedfbackftofisolatedfstudiesfoff specificfdiseasesfinfthefearlyf19thfcentury.fThes
efinvestigationsfculminatedfinfthefcelebratedfstudyfbyfJohnfSnowf(referredf tof
asf thef fatherf offepidemiology)f who,faroundfthef1850s,f observedf patternsfof
fincidencef offafcholerafoutbreakfinfcentralfLondon.fAsfafresultfoffhisfrecordingf
offthefincidencefoffcholerafandf mortalityfinfthefarea,f Snowfwasf ableftofisolate
fthefcausefoffthefcholerafepidemicfwhichfwasfattributedftofafcommunal fwater-
pumpfinfBroadfStreet,fSoho.fAfterfremovingf thef pumpf handle,fSnowfobserv
edfthatfnewfcasesfoffcholerafinfthefareafceasedfandfthefepidemicf declined.
Althoughfdismissedfbyfmostfscientistsfoff thef time,f thisf findingf andfothersf r
elatedf tof diseasef andf thef environmentf hadf af profoundf effectf onfthefformati
onfoffthefpublicfhealthfmovementfandfthefearlyfPublicfHealthfActsfoff1848f and
f1875.
Originally,ftheftermfepidemiologyfmeantfthefstudyfoffepidemics,fbutftheftechn
iquesf havef longf beenf improvedf upon.f Itf isf anf appliedf disciplinef andfafbasicfs
ciencefoffpreventivefandfsocialfmedicinef(notftheoretically)fandfmethodsfarefe
ssentiallyfobservational.fThus,fthefmodernfdefinitionfoffepidemiologyf accom
modatesf threef importantf elementsfffnamely:finclusionfoffallfdiseases,fpopulat
ions,f andfecologicalf approach.f Pleasefnotefthefthreefcomponentsf(3Ds)fcom
monftofthefdefinitionf offepidemiology:f diseaseffrequency,f distributionf andfd
eterminants.
Thef majorf questionsf thatf aref usuallyf askedf inf epidemiologyf are:f whof arefthe
fgroupfoffpersonf(s)faffectedfbyfthefdisease, fwherefhasfthefincidencefoccurred? f
Andfwhenf(time)fdidfitfoccur?
2
,PHSf 318 EPIDEMIOLOGYf FORf COMMUNITYf HEALTH
SELF-ASSESSMENTf EXERCISE
Highlightf thef3fimportantf componentf off epidemiology
3.2 Why Do We Study the 3 Components in Epidemiology?
f f f f f f f f
Theffollowingfreasonsfhavefbeenfadducedfforfstudyingfthesefthreef‘Ds’:fdisea
seffrequency,fdistributionfandf determinantsf off diseasesf infhumanf popul
ation:
forfplanningf andf evaluationf offhealthf care
forfidentificationf offthefdeterminantsf offdiseasesff
orf evaluationf offmethodf offcontrollingf disease
forf observationf off thef naturalf historyf off af disease-
makingf upf offdiagnosisf andfprognosis
forfclassificationf offafdisease.
3.3 Uses of Epidemiology
f f
Youfmayfrecallffromfthefactivityfabovefthatfthefstudyfoff diseasefdistributionfa
ndfcausationfisf centralf tof epidemiology.f Thef broadfgroupingf offthefusesfoc
cursf inftheffollowingf areasf namely:
i. understandingf thef causationf off thef diseasef andf thef developmentfoff
hypothesisf andftheirftesting
ii. understandingf offgeographicalf orflocalf patternsf offthef diseases
iii. administrationf (i.e.)f thef planningf offhealthf activitiesf andf directionfof
fprogrammef tofrelevantf sub-groupf identifiedf tof befatfrisk.
However,f epidemiologyf isfusedfforftheffollowing:
tof analysef thef respectivef rolef off agent,f hostf andf thef environmentfinft
hefdevelopmentf andfthefnaturalf historyfoffdisease
tof analysef thef occurrencef andf distributionf offdiseasef accordingf tofch
aracteristicsf suchf asfage,f sex,frace,f occupationf andfheredity
tofstudy,f outlinef andfdefinef problemsf offhealthf andf diseasef byfthefanal
ysisf offincidence,f prevalencef andf mortality
tofhelpf completef thefclinicalf featuref andf naturalf historyfoffdiseasefbyfgr
oupf analysis
tof estimatef anf individual‟sf riskf off developingf af diseasef andf hisfsurvi
valf chances
tof searchfforf factorsf relatedf tof healthf andf diseasef throughf thefobser
vationf off groupf customf andfhabits
forfplanningfandfallocationf offresources
3
, PHSf 318 EPIDEMIOLOGYf FORf COMMUNITYf HEALTH
tof evaluatef thef needf forf andf thef effectivenessf off healthf servicefthroug
hf fieldfstudies.
4.0 CONCLUSION
Thefscopefoffepidemiology,fitsfrangef off designsf andf impactf onfhealthcareff
ormationfandfreformationf hasf beenf immense.f Manyfhealthcarefrelatedf strat
egiesf andf policiesf thatf havef influencedfcommunityfhealthfpracticefoverfthef
pastfcenturyforfsofhavef beenfestablishedfasfafconsequencef off epidemiologica
lf study.f Itsf usesf alsofhavefcontributedftofincreasingfknowledgefonfhealthcar
e.fTheffactfthatfepidemiologyfisfseenftof bef morefholistic,f lessfstructured,f foc
usingf notfjustfonfindividuals,fbutfonfcommunities,fandflooksftowardsfpreventi
vefstrategies,finsteadfoffcurativefones,fmakesfitfanfidealfstrategyftofbefincorpor
atedf intofday-to-dayflifefexperiencesf andf professionalf practice.
5.0 SUMMARY
Thisfunitfhasftouchedfonfepidemiology,frationalefforfstudyingfthef3fDsfnamely
:fthefdiseaseffrequency,fdistributionf andfdeterminantsf asfwellf asfthefusesf forf t
hefoverallf improvementf offourfhealthcare.
6.0 TUTOR-MARKED ASSIGNMENT f
Discussf fivef (5)fimportancef offepidemiology.
7.0 REFERENCES/FURTHER READING f
Last,fJ.f(1994).fThefUsesfoffEpidemiology.fIn:fAshton,fJ.f(Ed.).fThefEpidemiol
ogicalfImagination.f Buckingham,f Openf UniversityfPress.
Lucasf &fGillesf (2003).f ShortfTextbookf offPublicfHealthf Medicinef forfthefT
ropics.f London:f Oxfordf Universityf Press.
Park,f K.f(2000).f Textbookf off Preventivef andf Socialf Medicine.f India:f M/sfBanarsi
dasf Bhanotf Publishers.
4
