RESULTScjblaze

RESEARCHImportedmalariaandhighriskgroups:observationalstudyusingUKsurveillancedata1987-2006AdrianDSmith,specialistregistrarinpublichealth,1DavidJBradley,emeritusprofessoroftropicalhygiene,1,2ValerieSmith,malariatraveladviser,1MarieBlaze,malariatraveladviser,1RonHBehrens,seniorlecturer,2PeterLChiodini,director,MalariaReferenceLaboratory,1,2ChristopherJMWhitty,professorofinternationalhealth1,2ABSTRACTObjectiveToexaminetemporal,geographic,andsociodemographictrendsincasereportingandcasefatalityofmalariaintheUnitedKingdom.
SettingNationalmalariareferencelaboratorysurveillancedataintheUK.
DesignObservationalstudyusingprospectivelygatheredsurveillancedataanddataondestinationsfromtheinternationalpassengersurvey.
Participants39300casesofprovedmalariaintheUKbetween1987and2006.
MainoutcomemeasuresPlasmodiumspecies;sociodemographicdetails(includingage,sex,andcountryofbirthandresidence);mortality;destination,duration,andpurposeofinternationaltravel;anduseofchemoprophylaxis.
ResultsReportedcasesofimportedmalariaincreasedsignificantlyoverthe20yearsofthestudy;anincreasingproportionwasattributabletoPlasmodiumfalciparum(Pfalciparum/Pvivaxreportingratio1.
3:1in1987-91and5.
4:1in2002-6).
Pvivaxreportsdeclinedfrom3954in1987-91to1244in2002-6.
CasefatalityofreportedPfalciparummalariadidnotchangeoverthisperiod(7.
4deathsper1000reportedcases).
Travellersvisitingfriendsandrelatives,usuallyinacountryinAfricaorAsiafromwhichmembersoftheirfamilymigrated,accountedfor13215/20488(64.
5%)ofallmalariareported,andreportsweregeographicallyconcentratedinareaswheremigrantsfromAfricaandSouthAsiatotheUKhavesettled.
Peopletravellingforthispurposewereatsignificantlyhigherriskofmalariathanothertravellersandwerelesslikelytoreporttheuseofanychemoprophylaxis(oddsratioofreportedchemoprophylaxisuse0.
23,95%confidenceinterval0.
21to0.
25).
ConclusionsDespitetheavailabilityofhighlyeffectivepreventivemeasures,thepreventableburdenfromfalciparummalariahassteadilyincreasedintheUKwhilevivaxmalariahasdecreased.
Provisionoftargetedandappropriatelydeliveredpreventivemessagesandservicesfortravellersfrommigrantfamiliesvisitingfriendsandrelativesshouldbeapriority.
INTRODUCTIONGlobally,malariaisestimatedtoaffect500millionpeopleandtocausemorethanonemilliondeathsayear.
1Malariaacquiredinendemicregionsandimportedintonon-endemiccountriesaccountsforaconsiderableandlargelypreventableburdenofmorbidityandmortalitythroughoutEuropeeveryyear.
Mostgeneralpractitionersareinvolvedinadvisingonprophylaxisagainstmalaria,andmostcliniciansintheUnitedKingdomwillbeinvolvedindiagnosingortreatingcasesofmalaria.
Theincreasingaccessibilityofinternationalairtravelandchangingpreferencesfortraveldestinationsmeanthatmorepeoplevisitregionsendemicformalaria,andtheydosoincreasinglyregularly.
2Travellerstoendemicareascanreducetheirriskofmalariasubstantiallybyadoptingpreventivemeasures:avoidingmosquitobitesandusingappropriatechemoprophylaxis.
3Effec-tiveuptakeofsuchmeasuresis,however,largelydependentonthetraveller'srecognitionandunder-standingoftherisk.
Thisinturndependsonanaccurateriskassessmentbyhealthcareworkerswhoadvisethem;theseriskschangeovertimewithshiftsintheglobalepidemiologyofmalaria,changesintravelhabitsandpatternsofmigration(visitstofriendsandrelativesareacommonreasonfortravel),andchangesinpatternsofdrugresistance.
WeexaminedmalarianotifiedintheUKin1987to2006inclusive,withtheaimofidentifyingimportanttrendsandatriskgroupstoassistpeopleadvisingtravellers(mainlygeneralpractitioners)andthoseseeingunwellreturnedtravellers(hospitaldoctorsandgeneralpractitioners).
Wehypothesisedthatthegroupoftravellersdescendedfrommigrantfamiliesvisitingfriendsandrelativesmightbeparticularlyatrisk.
METHODSTheMalariaReferenceLaboratory,partoftheHealthProtectionAgency,providesreferenceanddiagnosticparasitologyservicesandmaintainsthenationalsurveillancedatabaseofreportedcasesofmalariaintheUK.
Malariasurveillanceisapassivedetection1HPAMalariaReferenceLaboratory,LondonSchoolofHygieneandTropicalMedicine,LondonWC1E6AU2DepartmentofInfectiousandTropicalDiseases,LondonSchoolofHygieneandTropicalMedicineCorrespondence:ASmith,DivisionofPublicHealthandPrimaryCare,UniversityofOxford,OxfordOX37LFadrian.
smith@dphpc.
ox.
ac.
ukCitethisas:BMJ2008;337:a120doi:10.
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Downloadedfromsystemthatidentifiescasesfromstatutorynotification(throughlocalauthorities)andfromclinicianswhosendstandardisedmalariareportstotheMalariaReferenceLaboratory,usuallyaccompaniedbybloodfilmsforlaboratoryverification.
SystemsforcaseascertainmentformalariaintheUKarethoughttobeamongthemosteffectiveintheworld.
4Casedefinition,whichremainedidenticalovertheperiodcoveredbythisstudy,requiresparasitologicalcon-firmation(bloodfilmsortissuehistology).
Casestreatedpresumptivelyorsolelyreliantonalternativemeansofdiagnosis(suchasantigentests)arenotincluded.
Thenotifyinglaboratoryandclinicianarerequestedtoprovidefurtherinformation—personaldetails(dateofbirth,sex,countryofbirth,countryofusualresidence),detailsoftravel(dateofarrivalinUK,countryorregionvisited,purposeoftravel,durationoftravel),prophylaxistaken,anddetailsofillness(dateofonset,dateoftreatment,andmethodofdiagnosis).
Methodsofcasedetection,reporting,andtranscribingandtheinformationrequestedfromcareprovidersusedforthisanalysisremainedunchangedbetween1987and2006.
WeincludedallreportedepisodesofmalariaintheUKfrom1January1987to31December2006toprovide20consecutiveyears.
Supplementaryinformationcamefromrecordsofdeathcertificationforallmalariaassociateddeathsandfromrecordsofpostmortemfindingswhereavailable.
WeentereddataintodBaseIVandusedMicrosoftAccess10forcleaningandvalidation,includingidentificationofduplicatesandauditfortranscriptionerrors.
EstimatesofannualresidentialpopulationdenominatorsforEnglandandWales,Scotland,andNorthernIrelandfortheperiod1987-2006camefromrespectivenationalstatisticalcollections.
5-7DataonannualpassengernumbersfromtheUKtoindividual"malariouscountries"(asdefinedbytheWorldHealthOrganization8),bypurposeoftravel,toselectedcountriesinAfricaandSouthAsiacamefromtheinternationalpassengersurveyfortheyears1987to2006.
Thisisaquestionnairebasedsurveyofa0.
2%stratifiedsampleoftravellersusingBritishports;detailedsurveymethodsaredescribedelsewhere.
9WedidnotanalysesimilarinformationforvisitorstotheUK.
WeusedStata10fordataanalysis.
WeusedPearson'sχ2andMantel-Haenszelmethodsforbivari-ateanalysisofcategoricalvariables,withKruskall-Wallistestforequalityofpopulationsforcomparisonofnon-normallydistributedcontinuousvariables.
Weusedlinearregressionforanalysisoflineartrend.
Forbivariateanalysesforwhichdatawereincomplete,wecomparedmissingvalueswithcollectedvalues.
Wherereported,confidenceintervalsare95%andPvaluesaretwotailed.
RESULTSBetween1987and2006,39300casesofmalariawerereportedtotheMalariaReferenceLaboratory.
Datawerelargelycompleteforcentralvariables(age96%,sex94%,dateofdiagnosis98%,outcome99%)butlesscompleteforsomesupplementaryinformation(coun-tryofvisit88%,purposeoftravel71%,countryofbirth64%,prophylaxisuse62%).
Themedianageofcaseswas31years,and38%werefemale.
Malariawasattributabletoasinglespeciesin98.
7%ofcases:Pfalciparum24859(63%)cases,Pvivax10904(28%),Povale6%,Pmalariae1.
5%,andonecaseofPknowlesi.
Table1showsmortalitybyspeciesandtimeperiod.
Thepatternofmalariaspecieshaschangedmarkedlyoverthestudyperiod.
ReportsofPfalciparumincreasedthroughthestudyperiod(linearregression:β=+27.
4notifications/year,P<0.
0001);increasesforPovaleandTable1|ReportedcasesofmalariaanddeathsfromPlasmodiumfalciparummalaria,1987-2006PeriodReportedmalariacasesReportedcaserate,permillionUKpopulationDeathsduetoPfalciparumPfPvPoPmMixedSpeciesnotconfirmedTotalPfPvPoPmNoCasefatality(per1000cases)1987-915120395451310618612989117.
913.
91.
80.
4356.
81992-6554634756381521691998119.
212.
02.
20.
5417.
41997-2001744022316751608061059225.
47.
62.
30.
6597.
92002-6675312446101536968836*22.
54.
22.
00.
5487.
1Total24859109042436571504253930021.
39.
32.
10.
51837.
4Pf=Plasmodiumfalciparum;Pm=Plasmodiummalariae;Po=Plasmodiumovale;Pv=Plasmodiumvivax.
*IncludesonecaseofPknowlesi.
YearofreportReportsMilliontripstomalariouscountries(originatinginUK)1987198819891990199119921993199419951996199719981999200020012002200320042005200608001200160040002341PlasmodiumfalciparumPlasmodiumvivaxOtherspecies/mixedAnnualpassengernumbersLinear(Pfalciparum)R2=0.
563Linear(Pvivax)R2=0.
611Fig1|Reportedcasesofmalaria,1987to2006RESEARCHpage2of7BMJ|ONLINEFIRST|bmj.
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DownloadedfromPmalariaewerelesspronounced.
Incontrast,reportsofPvivaxdeclinedoverthestudyperiod(linearregres-sion:β=36.
2notifications/year,P<0.
0001)(fig1).
TheratioofPfalciparumtoPvivaxinfectionsincreasedfrom1.
3:1in1987-91to5.
4:1in2002-6.
Table2showsregionoftravelwheremalariawasacquired,byspecies;96%offalciparummalariawasacquiredinAfrica,whereas80%ofvivaxmalariacamefromSouthAsia.
Table3showsdataonreasonfortravel.
Wherereasonfortravelwasknown,20488cases,or75%ofimportedcases,occurredinUKtravellers(visitorsfromtheUKtomalariouscountries);theremainderwereamongvisitorstotheUK.
ThenumberofjourneystomalariouscountriesfromtheUKincreasedmarkedly(from593000visitsin1987to2.
6millionvisitsin2004),butthemediandurationofvisitstomalariousareasofcasesdecreased(1987-91,42days;1992-6,35days;1997-2001,28days;2002-6,28days).
OftheUKtravellerswhosereasonfortravelwasknown,13215(64.
5%,95%confidenceinterval64%to65%)hadtravelledtovisitfriendsorrelativesintheirownortheirfamilies'countryoforigin.
Most,butnotall,ofthesepeoplewerevisitingcountrieswheretheirfamilyhadsomedegreeofethnicorigin.
TheriskofmalariaperepisodeoftravelfromtheUKdecreasedbetween1987and2006forallspeciesofmalaria,mostnotablyforPvivax(fig2).
Ofthe34359caseswithreportedtravelhistory,24599(71.
6%,71%to72%)occurredaftertraveltoAfrica;thisincluded20774of21541(96.
4%,96%to97%)casesoffalciparummalaria.
SixtysevenpercentofmalariainUKtravellersaroseaftertraveltowestAfrica;traveltoNigeriaandGhanaaccountedfor54%ofallimportedPfalciparum.
OfthosepeoplewhoacquiredmalariainwestAfrica,76%werevisitingfriendsorrelativesintheirownortheirfamilies'countryoforigin,whereastourismwasthemostcommonpurposeoftravelforpeoplevisitingsouthernAfrica(48%)andeastAfrica(44%).
PeoplewhomadetripstovisitfamilyinAfricaweresignificantlymorelikelytohaveacquiredmalariathanthosetravellingforotherreasons(riskratioofreportsper10000trips=3.
65,95%confidenceinterval3.
5to3.
8;P<0.
0001).
TraveltoSouthAsiaaccountedfor8452cases,24.
6%,(24%to25%)ofimportedmalaria,ofwhich92%wasPvivax.
Overthestudyperiod,importedcasesfromthisregiondeclinedsignificantlyforallspeciesofmalariadespiteasustainedincreaseinvolumeoftravel.
From1987to1991,3036vivaxcasesarosefromtheIndiansubcontinent,accountingfor31%ofallUKmalaria.
By2002-6,thishaddecreasedto705cases(8%ofallUKmalaria).
Ofcasesinwhichthepurposeoftravelwasreported,89%ofUKtravellersvisitingSouthAsiahaddonesotovisitfamilyandfriends.
Peopletravellingforthisreasonwereatsignificantlyhigherriskofacquiringmalariathanothertravellers(riskratioofreportedcasesper10000trips=7.
9,7.
2to8.
6;χ2P<0.
0001).
OfUKtravellerswithcompleterecords(17129),only42%reportedtakinganyformofchemoprophy-laxisagainstmalariaduringtheirperiodoftravel.
Significantdifferencesexistedintheuseofchemopro-phylaxis(includingnon-standarddrugs)accordingtothegeographicaloriginofcases(table4),andpeoplewhohadvisitedfamilyintheircountryoforiginwerelesslikelytoreporttheuseofanyprophylaxisthanothertravellers(Mantel-Haenszeloddsratioadjustedforageandsex=0.
23,95%confidenceinterval0.
20to0.
25).
Amongreportedcasesinpeoplewhotravelledtosub-SaharanAfricabetween1999and2006,overwhichperiodconsistentrecommendationsonTable2|Reportedcasesofmalaria1987-2006,byglobalregionvisited(wherereported*).
Valuesarenumbers(percentages)RegionPlasmodiumfalciparumPlasmodiumvivaxPlasmodiumovalePlasmodiummalariaeTotalAfrica20774(96.
4)950(9.
7)2058(98.
0)480(98.
0)24599SouthAsia517(2.
4)7813(80.
1)23(1.
1)3(0.
6)8452FarEastandSouthEastAsia114(0.
5)387(4.
0)7(0.
3)2(0.
4)524CentralandSouthAmerica35(0.
2)304(3.
1)3(0.
1)3(0.
6)350Oceania46(0.
2)263(2.
7)7(0.
3)1(0.
2)333MiddleEast51(0.
2)39(0.
4)3(0.
1)1(0.
2)97Caribbean4(0.
01)0004Total215419756210149034359*Excludes4927reportswithnotravelinformationreportedand14reportswithnoknownhistoryoftravel.
IncludesonePknowlesi,455mixedspecies,and15unconfirmedspeciesreports.
Afghanistan,Burma(Myanmar),Bhutan,India,Pakistan,Bangladesh,Nepal,andSriLanka.
YearofreportReportsper10000trips198719891991199319951997199920012003200501015205TripstoIndia,Pakistan,andBangladeshTripstoothermalariouscountries(WHO)Fig2|RiskofreportedPlasmodiumvivaxpertravelepisodetoregionsendemicformalariaRESEARCHBMJ|ONLINEFIRST|bmj.
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Downloadedfromprophylacticdrugsforthisregionweremade,only7%ofpeoplevisitingfriendsorrelativesintheirownortheirfamilies'countryoforiginreportedhavingusedrecommendeddrugs,comparedwith24%ofpeopletravellingforotherreasons(χ2P<0.
0001).
Probablyreflectingthedistributionoffirstgenera-tionandsecondgenerationimmigrantgroups,astrikinggeographicaldistributionofcasesoccursintheUK(table5).
FortyonepercentofallcasesofmalariaintheUK,and65%ofcasesofPfalciparummalaria,occurredinLondonresidentsorvisitorstoLondon,whereasmost(68%)casesofPvivaxwerereportedfromotherregionsoftheUK,notablytheWestMidlands(aregionencompassingthedenselypopulatedconurbationsofBirmingham,Wolver-hampton,Coventry,andStoke-on-Trent).
Theseason-alityofPfalciparumcasesshowsabimodalpattern,withpeaksinJanuaryandSeptember,mirroringpatternsoftraveltodestinationswheretransmissionofPfalci-parumoccursthroughouttheyear(fig3).
Bycontrast,patternsofmonthlyPvivaxreportingshowasinglesummerpeak,parallelingthepeaktransmissionperiodsofmalariainmuchofIndiaandPakistan.
Mortalitydatashowthat183malariarelateddeathsoccurredovertheperiodofthestudy,givinganoverallcasefatalityrateforPfalciparummalariaof7.
4(95%confidenceinterval6.
3to8.
5)per1000cases;wefoundnoevidenceofasignificantchangeovertheperiodofstudy.
CasefatalitywassignificantlyloweramongpeopletravellingfromtheUKtovisitfriendsorrelativesintheirownortheirfamilies'countryoforiginthanamongpeopletravellingforotherreasons(0.
25%v1.
9%;χ2=83.
1,P<0.
001).
DISCUSSIONThisstudyofmorethan39000casesofmalariaimportedintotheUKshowsstrikingtrends.
Pfalciparummalariahasincreasedsteadily,whichisaconcernbecausethesecasesarepotentiallyfatal;everyyearwhollypreventabledeathsdoensueintheUK.
Reportedcasesarenotdistributedevenlyacrossthepopulationbutareheavilyconcentratedincommu-nitieswithfrequenttraveltoseefriendsandrelatives,especiallyinwestAfrica.
TravellerstoNigeriaandGhana,neitherofwhichisacommontouristdestina-tion,accountforhalfofallimportedfalciparumcases.
Aminorityoftravellerswithmalariareporthavingusedanyprophylaxis,andmuchofthatusedisinadequate.
Whereasfalciparumisincreasing,vivaxmalariaimportedintotheUKhasdroppeddramati-cally.
Vivaxmalariaisalsoadiseaseofpeoplevisitingfriendsandrelatives;incontrasttofalciparummalaria,mostcasesareinpeoplewhoresideoutsideLondon.
DisproportionalburdenofmalariainwestAfricandiasporaThesedatarepresentapublichealthfailingbutalsoanopportunity.
Theyshowthathealthmessagesarenotgettingthroughtoethnicminoritygroupsvisitingfriendsandrelatives,especiallyinwestAfrica.
Targetingmessagestailoredtothesegroupsisessentialinprimarycareandpublichealth;thisshouldbepossibleandwouldhaveasubstantialimpactonmalariaintheUK.
AhalvingofmalariainpeopleintheAfricandiasporavisitingfriendsandrelativeswouldreducemalariainUKtravellersbyalmostaquarter.
PeoplevisitingfriendsorTable3|Purposeoftravelamongreportedcasesofmalaria,1987-2006(wherereported*)Median(interquartilerange)durationofstay(days)CasesDeathsduetoPlasmodiumfalciparumPercentage(95%CI)casesreportinguseofprophylaxis*(limitedsample)TraveloriginatinginUKTraveloriginatingoutsideUKVisitingfamilyincountryoforigin28(21-58)132152528.
4(27.
5to29.
2)Holidaytomalariouscountry21(14-56)40297268.
5(67.
0to70.
0)Business/professionaltravel60(21-168)21052461.
6(59.
4to63.
8)ForeignstudentinUK28(15-70)5480NABritisharmedforces46(28-110)374192.
6(89.
1to95.
1)Childrenvisitingparentslivingabroad28(21-42)148046.
6(37.
9to55.
4)Civiliansea/aircrew14(7-81)69243.
6(30.
0to57.
7)ForeignvisitorillwhileinUK28333115NANewentranttoUKNA26023NAUKcitizenlivingabroadNA10101546.
8(43.
6to50.
1)NA=notapplicable.
*Excludes11869reportsand26deathsforwhichpurposeoftravelwasnotstatedortravelhadnotoccurred.
Table4|Useofchemoprophylaxis*amongtravellersfromUK,byregionofbirthplaceRegionofbirthCasesProphylaxistakenYesPercentage(95%CI)Europe5674349361.
6(60to63)Africa5914169928.
7(28to30)SouthAsia231554923.
7(22to26)Otherregions38722357.
6(53to63)Total14290596441.
7(41to42)*Includesbothrecommendedandnon-standarddrugs.
Excludes3359casereportswithnoreportedchemoprophylaxisinformationand4285withnobirthplacereported.
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Downloadedfromrelativesintheirownortheirfamilies'countryoforiginmaywellexpecttovisitsettingswithahigherriskoftransmissionofmalariathanothertravellersandtodosoforlongerperiods10-12;thatmanydothiswithoutthebenefitofeffectiveantimalarialchemoprophylaxis,astheseandotherdatasuggest,13-16isofconcern.
Someevidenceshowsthatpeoplevisitingfriendsorrelativesintheirownortheirfamilies'countryoforiginarelesslikelythantouriststoselfrefertotravelhealthservicesbeforedeparture,17arelesslikelytotakeupprophylaxisbeforetheytravel,18-20andadherelesstopreventivemeasureswhileabroad.
21Thepersonalcostofrecom-mendedchemoprophylaxisandfearsofsideeffectshavebeensuggestedasdirectdisincentivesthatdisproportio-natelyaffecthighriskgroups.
2223However,littleinformationisavailableontheculturalandethnicbasisofknowledge,attitudes,andpracticeregardingmalariaanditsprevention.
BeliefsamongadulttravellersborninAfricathattheyremainprotectedfromthesevereconsequencesofmalariaandthatmalariaisatrivialcomplainthavebeenreported.
2425Asthedatareportedhereshow,peopleofAfricanorigindogetmalariaandindeedhaveamuchhigherriskofdoingsothanothertravellerstoAfrica.
Althoughthesedataareconsistentwiththefindingsofotherstudiesthatshowtravellersacquiringmalariaonreturntotheircountryoforigintohavealowercasefatalityratefrommalariathanothertravellinggroups,1226deathsdooccur.
27Basingpre-traveladviceonanassessmentofthetraveller'spreviousexposuretomalariacannotbejustified,andfalciparummalariashouldalwaysbemanagedasapreventable,poten-tiallylifethreateningdisease.
328DisappearanceofvivaxcasesimportedfromAsiaWhereastheincreaseinfalciparumcasesfromAfricacanbeexplainedbyincreasesintraveltohighlyendemiccountries,changesintravelvolumecannotexplainthedeclineinvivaxmalaria.
ThesynchronousdecreaseinPfalciparumnotificationsfromIndiaandPakistansuggeststhatthedecreasesarenotsimplyduetodifferentialnotificationorhospitaladmissionpoliciesforcasescausedbydifferentmalariaspeciesbutprobablyreflectatruereductionintheriskofexposuretomalariaduringtravel.
AnnualprevalencereportsformalariaoverthesameperiodhavedocumentedmodestdeclinesinSouthAsia(thoughttohaveresultedfromvigorouslocalcontrolefforts,increasingurbanisation,andrisingeconomicprosperity),8-29butnothingapproachingthedramaticfallseenincasesimportedtotheUKandEurope.
30Oneexplanationmightbethattravellersvisitingfamilyintheregionincreasinglystayinurbansettingswherelocalcontrolmeasureshavebeenmosteffectiveinreducinglocaltransmissionofmalaria.
InthelightofthereductionintheriskofimportedmalariafromSouthAsia,therisk-benefitassessmentoftheroutineadviceonchemoprophylaxisfortheregionmayneedtobere-examined,ashasbeenthecaseforLatinTable5|ReportedmalariacasesbyUKregion,1987-2006*UKregionReportedmalariacasesReportedcasesper1000000population(mid-yearestimates,1987-2006)PfPvPoPmAllspeciesPfPvPoPmAllspeciesEngland:Southwest9413101272214199.
73.
21.
30.
214.
7Southeast3107128735485489619.
88.
22.
30.
531.
2EastofEngland155381317230260414.
77.
71.
60.
324.
7WestMidlands716226371930916.
821.
50.
70.
129.
3EastMidlands37845148129064.
65.
50.
60.
111.
0YorkshireandtheHumber5541003741416615.
610.
10.
70.
116.
7Northwest3005382188782.
23.
90.
20.
16.
4Northeast115601111902.
21.
20.
20.
023.
7London158433463138035521345112.
124.
59.
82.
5151.
0Wales2521183884234.
42.
00.
70.
17.
3Scotland48033867159134.
73.
30.
70.
19.
0NIreland7337911202.
21.
10.
30.
033.
6Total243121068123725603844620.
89.
12.
00.
432.
9Pf=Plasmodiumfalciparum;Pm=Plasmodiummalariae;Po=Plasmodiumovale;Pv=Plasmodiumvivax.
*Excludes854caseswithmissingpostcode.
MonthofreportProportionofannualreportspermonth(%)0812164PlasmodiumfalciparumPlasmodiumvivaxOtherconfirmedspeciesJanFebMarAprMayJunJulAugSepOctNovDecFig3|CalendarmonthofonsetofreportedmalariaintheUK,1987to2006RESEARCHBMJ|ONLINEFIRST|bmj.
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31Nevertheless,casesofmalariacontinuetooccurandtravellersneedtobewarnedtohaveanyfeverinvestigatedrapidlyformalaria.
LimitationsofstudyTheadvantagesoflargescale,prospectivelycollecteddatafromsurveillancecentrescollectedinanunchanged,standardisedwayoverlongperiodsareclear,butlimitationsalsoexist.
Under-reportingisinevitable,32andlaboratoriesandcliniciansdifferinthecomprehensivenessoftheirreporting.
PreviousstudiesofdatafromtheMalariaReferenceLaboratorysuggestthattheyaremorecompletethanmostotherroutinelycollecteddataonmalariaandareinexcessof50%complete.
4Nevertheless,thetrueburdenofmalariaintheUKisalmostcertainlyhigherthanthesesurveillanceresultssuggest.
Asthemethodsdidnotchangeoverthisperiod,however,thisisunlikelytoaffecttrendsreportedhere,particularlytherelativeincreaseinonespeciesanddeclineinanotherseeninthisstudy,ortoexplaintheheavyconcentrationofcasesinpeoplevisitingfriendsandrelatives.
Reportingcliniciansoftendidnotreportinformationabouttravelhistoryandprophylaxis,butwefoundnoevidencetosuggestthatcaseswithmissinginformationweresystematicallydifferentfromthosewithcompletereports.
Evenwheninformationaboutpreventivemeasuresisrequestedoftravellers,adher-encetosuchmeasuresmaybedifficulttoassess.
ImplicationsoffindingsThisstudyhighlightstheneedforgeneralpractitionersandpeopleinvolvedinpublichealthtofocustailoredmessagesonpreventingmalariaonmembersanddescendantsofmigrantfamiliesvisitingfriendsandrelatives,especiallyinAfricanmigrantfamilies.
TheUKhasguidelinesbasedonconsensusthathighlighttheneedforallUKresidents,irrespectiveofcountryofbirth,touseeffectiveantimalarialprophylaxiswhenvisitinghighlyendemicareas.
33Changestopublichealthpolicy,includingthecurrentpolicyofchargingforantimalarialprophylaxis,mayneedtobeconsidered.
Malariaisanalmostentirelypreventable,potentiallyfatal,diseasethatposesaconsiderablerisktosomemigrantgroups.
WethankallthelaboratoriesandclinicianswhoprovidedatatotheMalariaReferenceLaboratory.
Contributors:ADS,MB,andVSenteredandanalysedthedata,withcontributionsfromCJMWandRHB.
DJBdevelopedandsuperviseddatacollectionupto2003,andCJMWdidsothereafter.
ADSandCJMWdraftedthepaper,withcontributionsfromallauthors.
CJMWistheguarantor.
Funding:CJMWissupportedbytheGatesMalariaPartnership,andDJBisaLeverhulmeemeritusfellow.
AllothersupportisfromtheHealthProtectionAgency.
Competinginterests:Nonedeclared.
Ethicalapproval:Notneeded.
Provenanceandpeerreview:Notcommissioned;externallypeerreviewed.
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