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SwineFlu(SwineInfluenzaA[H1N1andH3N2v]Virus)MedicalAuthor:CharlesPatrickDavis,MD,PhD

CharlesPatrickDavis,MD,PhD

Dr.Charles"Pat"Davis,MD,PhD,isaboardcertifiedEmergencyMedicinedoctorwhocurrentlypracticesasaconsultantandstaffmemberforhospitals.HehasaPhDinMicrobiology(UTatAustin),andtheMD(Univ.TexasMedicalBranch,Galveston).HeisaClinicalProfessor(retired)intheDivisionofEmergencyMedicine,UTHealthScienceCenteratSanAntonio,andhasbeentheChiefofEmergencyMedicineatUTMedicalBranchandatUTHSCSAwithover250publications.

ViewFullProfileMedicalEditor:MelissaConradStppler,MD

MelissaConradStppler,MD

MelissaConradStppler,MD,isaU.S.boardcertifiedAnatomicPathologistwithsubspecialtytraininginthefieldsofExperimentalandMolecularPathology.Dr.Stppler'seducationalbackgroundincludesaBAwithHighestDistinctionfromtheUniversityofVirginiaandanMDfromtheUniversityofNorthCarolina.ShecompletedresidencytraininginAnatomicPathologyatGeorgetownUniversityfollowedbysubspecialtyfellowshiptraininginmoleculardiagnosticsandexperimentalpathology.

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Swineflu(H1N1andH3N2vinfluenzavirus)factsWhatistheswineflu?Whatcausesswineflu?Whyisswineflunowinfectinghumans?Whatarethesymptomsofswineflu?Howisswinefludiagnosed?Whatisthetreatmentforswineflu?Whatisthehistoryofswinefluinhumans?Whataretheriskfactorsforswineflu?Canswineflubepreventedwithavaccine?Canswineflubepreventediftheswinefluvaccine(orotherflustrainvaccines)isnotreadilyavailable?Wasswineflu(H1N1)acauseofanepidemicorpandemicinthe20092010fluseason?Whatistheprognosis(outlook)andcomplicationsforpatientswhogetswineflu?Whatisthelatestnewsaboutswineflu?WherecanIfindmoreinformationaboutswineflu(H1N1andH3N2v)?PicturesofStreporSoreThroatSlideshow

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Swineflu(H1N1andH3N2vinfluenzavirus)facts

Swinefluisarespiratorydiseasecausedbyinfluenzavirusesthatinfecttherespiratorytractofpigsandresultinabarkingcough,decreasedappetite,nasalsecretions,andlistlessbehaviortheviruscanbetransmittedtohumans.Swinefluvirusesmaymutate(change)sothattheyareeasilytransmissibleamonghumans.The2009swinefluoutbreak(pandemic)wasduetoinfectionwiththeH1N1virusandwasfirstobservedinMexico.Symptomsofswinefluinhumansaresimilartomostinfluenzainfections:fever(100Forgreater),cough,nasalsecretions,fatigue,andheadache.Vaccinationisthebestwaytopreventorreducethechancesofbecominginfectedwithinfluenzaviruses.Twoantiviralagents,zanamivir(Relenza)andoseltamivir(Tamiflu),havebeenreportedtohelppreventorreducetheeffectsofswinefluiftakenwithin48hoursoftheonsetofsymptoms.Therearevariousmethodslistedinthisarticletohelpindividualsfromgettingtheflu.Themostseriouscomplicationofthefluispneumonia.

Whatistheswineflu?

Swineflu(swineinfluenza)isarespiratorydiseasecausedbyviruses(influenzaviruses)thatinfecttherespiratorytractofpigs,resultinginnasalsecretions,abarkingcough,decreasedappetite,andlistlessbehavior.Swinefluproducesmostofthesamesymptomsinpigsashumanfluproducesinpeople.Swineflucanlastaboutonetotwoweeksinpigsthatsurvive.Swineinfluenzaviruswasfirstisolatedfrompigsin1930intheU.S.andhasbeenrecognizedbyporkproducersandveterinarianstocauseinfectionsinpigsworldwide.Inanumberofinstances,peoplehavedevelopedtheswinefluinfectionwhentheyarecloselyassociatedwithpigs(forexample,farmers,porkprocessors),andlikewise,pigpopulationshaveoccasionallybeeninfectedwiththehumanfluinfection.Inmostinstances,thecrossspeciesinfections(swinevirustomanhumanfluvirustopigs)haveremainedinlocalareasandhavenotcausednationalorworldwideinfectionsineitherpigsorhumans.Unfortunately,thiscrossspeciessituationwithinfluenzaviruseshashadthepotentialtochange.Investigatorsdecidedthe2009socalled"swineflu"strain,firstseeninMexico,shouldbetermednovelH1N1flusinceitwasmainlyfoundinfectingpeopleandexhibitstwomainsurfaceantigens,H1(hemagglutinintype1)andN1(neuraminidasetype1).TheeightRNAstrandsfromnovelH1N1fluhaveonestrandderivedfromhumanflustrains,twofromavian(bird)strains,andfivefromswinestrains.

Swinefluistransmittedfrompersontopersonbyinhalationoringestionofdropletscontainingvirusfrompeoplesneezingorcoughingitisnottransmittedbyeatingcookedporkproducts.ThenewestswinefluvirusthathascausedswinefluisinfluenzaAH3N2v(commonlytermedH3N2v)thatbeganasanoutbreakin2011.The"v"inthenamemeansthevirusisavariantthatnormallyinfectsonlypigsbuthasbeguntoinfecthumans.TherehavebeensmalloutbreaksofH1N1sincethepandemicarecentoneisinIndiawhereatleastthreepeoplehavedied.

Whatcausesswineflu?

Thecauseofthe2009swinefluwasaninfluenzaAvirustypedesignatedasH1N1.In2011,anewswinefluviruswasdetected.ThenewstrainwasnamedinfluenzaA(H3N2)v.Onlyafewpeople(mainlychildren)werefirstinfected,butofficialsfromtheU.S.CentersforDiseaseControlandPrevention(CDC)reportedincreasednumbersofpeopleinfectedinthe20122013fluseason.Currently,therearenotlargenumbersofpeopleinfectedwithH3N2v.Unfortunately,anothervirustermedH3N2(noteno"v"initsname)hasbeendetectedandcausedflu,butthisstrainisdifferentfromH3N2v.Ingeneral,alloftheinfluenzaAviruseshaveastructuresimilartotheH1N1viruseachtypehasasomewhatdifferentHand/orNstructure.

Whyisswineflunowinfectinghumans?

Manyresearchersnowconsiderthattwomainseriesofeventscanleadtoswineflu(andalsoavianorbirdflu)becomingamajorcauseforinfluenzaillnessinhumans.

First,theinfluenzaviruses(typesA,B,C)areenvelopedRNAviruseswithasegmentedgenomethismeanstheviralRNAgeneticcodeisnotasinglestrandofRNAbutexistsaseightdifferentRNAsegmentsintheinfluenzaviruses.Ahuman(orbird)influenzaviruscaninfectapigrespiratorycellatthesametimeasaswineinfluenzavirussomeofthereplicatingRNAstrandsfromthehumanviruscangetmistakenlyenclosedinsidetheenvelopedswineinfluenzavirus.Forexample,onecellcouldcontaineightswinefluandeighthumanfluRNAsegments.ThetotalnumberofRNAtypesinonecellwouldbe16fourswineand

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fourhumanfluRNAsegmentscouldbeincorporatedintooneparticle,makingaviableeightRNAsegmentedfluvirusfromthe16availablesegmenttypes.VariouscombinationsofRNAsegmentscanresultinanewsubtypeofvirus(thisprocessisknownasantigenicshift)thatmayhavetheabilitytopreferentiallyinfecthumansbutstillshowcharacteristicsuniquetotheswineinfluenzavirus(seeFigure1).ItisevenpossibletoincludeRNAstrandsfrombirds,swine,andhumaninfluenzavirusesintoonevirusifasinglecellbecomesinfectedwithallthreetypesofinfluenza(forexample,twobirdflu,threeswineflu,andthreehumanfluRNAsegmentstoproduceaviableeightsegmentnewtypeoffluviralgenome).FormationofanewviraltypeisconsideredtobeantigenicshiftsmallchangeswithinanindividualRNAsegmentinfluvirusesaretermedantigenicdrift(seefigure1)andresultinminorchangesinthevirus.However,thesesmallgeneticchangescanaccumulateovertimetoproduceenoughminorchangesthatcumulativelyalterthevirus'makeupovertime(usuallyyears).

Second,pigscanplayauniqueroleasanintermediaryhosttonewflutypesbecausepigrespiratorycellscanbeinfecteddirectlywithbird,human,andothermammalianfluviruses.Consequently,pigrespiratorycellsareabletobeinfectedwithmanytypesoffluandcanfunctionasa"mixingpot"forfluRNAsegments(seefigure1).Birdfluviruses,whichusuallyinfectthegastrointestinalcellsofmanybirdspecies,areshedinbirdfeces.Pigscanpickthesevirusesupfromtheenvironment,andthisseemstobethemajorwaythatbirdfluvirusRNAsegmentsenterthemammalianfluviruspopulation.Figure1showsthisprocessinH1N1,butthefigurerepresentsthegeneticprocessforallfluviruses,includinghuman,swine,andavianstrains.

Figure1.

Whatarethesymptomsofswineflu?

Symptomsofswinefluaresimilartomostinfluenzainfections:fever(100Forgreater),cough,nasalsecretions,fatigue,andheadache,withfatiguebeingreportedinmostinfectedindividuals.Somepatientsmayalsogetasorethroat,rash,bodyaches,headaches,chills,nausea,vomiting,anddiarrhea.InMexico,manyoftheinitialpatientsinfectedwithH1N1influenzawereyoungadults,whichmadesomeinvestigatorsspeculatethatastrongimmuneresponse,asseeninyoungpeople,maycausesomecollateraltissuedamage.Theincubationperiodfromexposuretofirstsymptomsisaboutonetofourdays,withanaverageoftwodays.Thesymptomslastaboutonetotwoweeksandcanlastlongerifthepersonhasasevereinfection.

Somepatientsdevelopsevererespiratorysymptomsandneedrespiratorysupport(suchasaventilatortobreatheforthepatient).Patientscangetpneumonia(bacterialsecondaryinfection)iftheviralinfectionpersists,andsomecandevelopseizures.Deathoftenoccursfromsecondarybacterialinfectionofthelungsappropriateantibioticsneedtobeusedinthesepatients.Theusualmortality(death)ratefortypicalinfluenzaAisabout0.1%,whilethe1918"Spanishflu"epidemichadanestimatedmortalityraterangingfrom2%20%.Swine(H1N1)fluinMexicohadabout160deathsandabout2,500confirmedcases,whichwouldcorrespondtoamortalityrateofabout6%,buttheseinitialdatawererevisedandthemortalityrateworldwidewasestimatedtobemuchlower.Fortunately,themortalityrateofH1N1remainedlowandsimilartothatoftheconventionalflu(averageconventionalflumortalityrateisabout36,000peryear

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projectedH1N1flumortalityratewas90,000peryearintheU.S.asdeterminedbythepresident'sadvisorycommittee,butitneverapproachedthathighnumber).

Fortunately,althoughH1N1developedintoapandemic(worldwide)flustrain,themortalityrateintheU.S.andmanyothercountriesonlyapproximatedtheusualnumbersoffludeathsworldwide.Speculationaboutwhythemortalityrateremainedmuchlowerthanpredictedincludesincreasedpublicawarenessandactionthatproducedanincreaseinhygiene(especiallyhandwashing),afairlyrapiddevelopmentofanewvaccine,andpatientselfisolationifsymptomsdeveloped.

Howisswinefludiagnosed?

Swinefluispresumptivelydiagnosedclinicallybythepatient'shistoryofassociationwithpeopleknowntohavethediseaseandtheirsymptomslistedabove.Usually,aquicktest(forexample,nasopharyngealswabsample)isdonetoseeifthepatientisinfectedwithinfluenzaAorBvirus.MostofthetestscandistinguishbetweenAandBtypes.Thetestcanbenegative(nofluinfection)orpositivefortypeAandB.IfthetestispositivefortypeB,thefluisnotlikelytobeswineflu.IfitispositivefortypeA,thepersoncouldhaveaconventionalflustrainorswineflu.However,theaccuracyofthesetestshasbeenchallenged,andtheU.S.CentersforDiseaseControlandPrevention(CDC)hasnotcompletedtheircomparativestudiesofthesetests.However,anewtestdevelopedbytheCDCandacommercialcompanyreportedlycandetectH1N1reliablyinaboutonehourthetestwasformerlyonlyavailabletothemilitary.In2010,theFDAapprovedacommerciallyavailabletestthatcoulddetectH1N1withinfourhours.MostoftheserapidtestsarebasedonPCRtechnology.

Swinefluisdefinitivelydiagnosedbyidentifyingtheparticularantigens(surfaceproteins)associatedwiththevirustype.Ingeneral,thistestisdoneinaspecializedlaboratoryandisnotdonebymanydoctors'officesorhospitallaboratories.However,doctors'officesareabletosendspecimenstospecializedlaboratoriesifnecessary.BecauseofthelargenumberofnovelH1N1swineflucasesthatoccurredinthe20092010fluseason(thevastmajorityofflucases[about95%99%]wereduetonovelH1N1fluviruses),theCDCrecommendedonlyhospitalizedpatients'fluvirusstrainsbesenttoreferencelabstobeidentified.H3N2vflustrainsandotherfluvirusstrainsarediagnosedbysimilarmethods.

Whatisthetreatmentforswineflu?

Thebesttreatmentforinfluenzainfectionsinhumansispreventionbyvaccination.Workbyseverallaboratorieshasproducedvaccines.ThefirstH1N1vaccinereleasedinearlyOctober2009wasanasalsprayvaccinethatwasapprovedforuseinhealthyindividualsages249.Theinjectablevaccine,madefromkilledH1N1,becameavailableinthesecondweekofOct.2009.Thisvaccinewasapprovedforuseinages6monthstotheelderly,includingpregnantfemales.BothofthesevaccineswereapprovedbytheCDConlyaftertheyhadconductedclinicaltrialstoprovethatthevaccinesweresafeandeffective.Anewinfluenzavaccinepreparationistheintradermal(trivalent)vaccineisavailableitworksliketheshotexcepttheadministrationislesspainful.Itisapprovedforages1864years.

Almostallvaccineshavesomesideeffects.CommonsideeffectsofH1N1vaccines(aloneorincombinationwithotherfluviralstrains)aretypicaloffluvaccinesusedovermanyyearsandareasfollows:

Flushot:Soreness,redness,minorswellingattheshotsite,muscleaches,lowgradefever,andnauseadonotusuallylastmorethanabout24hours.Nasalspray:runnynose,lowgradefever,vomiting,headache,wheezing,cough,andsorethroatIntradermalshot:redness,swelling,pain,headache,muscleaches,fatigue

Theflushot(vaccine)ismadefromkilledvirusparticlessoapersoncannotgettheflufromaflushot.However,thenasalsprayvaccinecontainslivevirusthathavebeenalteredtohinderitsabilitytoreplicateinhumantissue.Peoplewithasuppressedimmunesystemshouldnotgetvaccinatedwiththenasalspray.Also,mostvaccinesthatcontainfluviralparticlesarecultivatedineggs,soindividualswithanallergytoeggsshouldnotgetthevaccineunlesstestedandadvisedbytheirdoctorthattheyareclearedtoobtainit.Likeallvaccines,rareeventsmayoccurinsomerarecases(forexample,swelling,weakness,orshortnessofbreath).Ifanysymptomslikethesedevelop,thepersonshouldseeaphysicianimmediately.

Twoantiviralagentshavebeenreportedtohelppreventorreducetheeffectsofswineflu.Theyarezanamivir(Relenza)andoseltamivir(Tamiflu),bothofwhicharealsousedtopreventorreduceinfluenzaAandBsymptoms.Thesedrugsshouldnotbeusedindiscriminately,becauseviralresistancetothemcanandhasoccurred.Also,theyarenotrecommendediftheflusymptomsalreadyhavebeenpresentfor48hoursormore,althoughhospitalizedpatientsmaystillbetreatedpastthe48hourguideline.Severeinfectionsinsomepatientsmayrequireadditionalsupportivemeasuressuchasventilationsupportandtreatmentofotherinfectionslikepneumoniathatcanoccurinpatientswithaseverefluinfection.TheCDChassuggestedintheirguidelinesthatpregnantfemalescanbetreatedwiththetwoantiviralagents.

OnDec.22,2014,theFDAapprovedthefirstnewantiinfluenzadrug(forH1N1andotherinfluenzavirus

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types)in15years,peramivirinjection(Rapivab).Itisapprovedforuseinthefollowingsettings:

Diarrhea,skininfections,hallucinations,and/oralteredbehaviormayoccurassideeffectsofthisdrug.

Adultpatientsforwhomtherapywithanintravenous(IV)medicationisclinicallyappropriate,basedupononeormoreofthefollowingreasons:

Thepatientisnotrespondingtoeitheroralorinhaledantiviraltherapy,ordrugdeliverybyarouteotherthanIVisnotexpectedtobedependableorisnotfeasible,orthephysiciandecidesthatIVtherapyisappropriateduetoothercircumstances.

Pediatricpatientsforwhomanintravenousmedicationclinicallyappropriatebecause:Thepatientisnotrespondingtoeitheroralorinhaledantiviraltherapy,ordrugdeliverybyarouteotherthanIVisnotexpectedtobedependableorisnotfeasible.

Whatisthehistoryofswinefluinhumans?

In1976,therewasanoutbreakofswinefluatFortDix.Thisviruswasnotthesameasthe2009H1N1outbreak,butitwassimilarinsofarasitwasaninfluenzaAvirusthathadsimilaritiestotheswinefluvirus.TherewasonedeathatFortDix.Thegovernmentdecidedtoproduceavaccineagainstthisvirus,butthevaccinewasassociatedwithrareinstancesofneurologicalcomplications(GuillainBarrsyndrome)andwasdiscontinued.Someindividualsspeculatethatformalin,usedtoinactivatethevirus,mayhaveplayedaroleinthedevelopmentofthiscomplicationin1976.Oneofthereasonsittakesafewmonthstodevelopanewvaccineistotestthevaccineforsafetytoavoidthecomplicationsseeninthe1976vaccine.Individualswithactiveinfectionsordiseasesofthenervoussystemarealsonotrecommendedtogetfluvaccines.

Earlyinthespringof2009,H1N1fluviruswasfirstdetectedinMexico,causingsomedeathsamonga"younger"population.Itbeganincreasingduringthesummer2009andrapidlyspreadtotheU.S.andtoEuropeandeventuallyworldwide.TheWHOdeclareditfirstfittheircriteriaforanepidemicandthen,inJune2009,theWHOdeclaredthefirstflupandemicin41years.Therewasaworldwideconcernandpeoplebegantoimproveinhandwashingandotherpreventionmethodswhiletheyawaitedvaccinedevelopment.Thetrivalentvaccinemadeforthe20092010fluseasonofferedvirtuallynoprotectionfromH1N1.Newvaccinesweredeveloped(bothliveandkilledvirus)andstartedtobecomeavailableinSept.2009Oct.2009.TheCDCestablishedaprotocolguidelineforthosewhoshouldgetthevaccinefirst.BylateDecembertoJanuary,avaccineagainstH1N1wasavailableinmoderatesupplyworldwide.Thenumbersofinfectedpatientsbegantorecedeandthepandemicended.However,astrainofH1N1wasincorporatedintotheyearlytrivalentvaccineforthe20102011fluseasonbecausetheviruswaspresentintheworldpopulations.

Asstatedinthefirstsectionofthisarticle,anewstrainofswineflu,(H3N2)v,wasdetectedin2011ithasnotaffectedanylargenumbersofpeopleinthecurrentfluseason.However,anotherantigenicallydistinctviruswiththesameHandNcomponents(termedH3N2(noteno"v")hascausedfluinhumansviralantigenswereincorporatedintothe20132014seasonalflushotsandnasalsprayvaccines.

Whataretheriskfactorsforswineflu?

Vaccinationtopreventinfluenzaisparticularlyimportantforpeoplewhoareatincreasedriskforseverecomplicationsfrominfluenzaorathigherriskforinfluenzarelateddoctororhospitalvisits.Whenvaccinesupplyislimited,vaccinationeffortsshouldfocusondeliveringvaccinationtothefollowingpeoplesincethesepopulationshaveahigherriskforH1N1andsomeotherviralinfectionsaccordingtotheCDC:

Allchildren6monthsto4years(59months)ofageAllpeople50yearsofageandolderAdultsandchildrenwhohavechronicpulmonary(includingasthma)orcardiovascular(exceptisolatedhypertension),renal,hepatic,neurological,hematologic,ormetabolicdisorders(includingdiabetesmellitus)Peoplewhohaveimmunosuppression(includingimmunosuppressioncausedbymedicationsorbyHIV)WomenwhoareorwillbepregnantduringtheinfluenzaseasonChildrenandadolescents(6monthsto18yearsofage)whoarereceivinglongtermaspirintherapyandwhomightbeatriskforexperiencingReye'ssyndromeafterinfluenzavirusinfectionResidentsofnursinghomesandotherlongtermcarefacilitiesAmericanIndians/AlaskanativesPeoplewhoaremorbidlyobese(BMI40)Healthcareprofessionals(doctors,nurses,healthcarepersonneltreatingpatients)Householdcontactsandcaregiversofchildrenunder5yearsofageandadults50yearsof

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ageandolder,withparticularemphasisonvaccinatingcontactsofchildrenlessthan6monthsageHouseholdcontactsandcaregiversofpeoplewithmedicalconditionsthatputthemathigherriskforseverecomplicationsfrominfluenza

Canswineflubepreventedwithavaccine?

TheCDCrecommendsforthe20142015fluseasonthateveryone6monthsoldandoldershouldgetaflushottopreventorreducethechanceofgettingtheflu.ThebestwaytopreventnovelH1N1swinefluisvaccination.The2014CDCrecommendationsthatapplytoH1N1,H3N2,andotherfluvirusesarealmostidenticaltothoseabovementionedrecommendationsforpatientsatriskwhenvaccinedosesarelimitedandareasfollows:

Areaged6monthsthrough4years(59months)Areaged50yearsandolderHavechronicpulmonary(includingasthma),cardiovascular(excepthypertension),renal,hepatic,neurologic,hematologic,ormetabolicdisorders(includingdiabetesmellitus)Areimmunosuppressed(includingimmunosuppressioncausedbymedicationsorbyhumanimmunodeficiencyvirus)AreorwillbepregnantduringtheinfluenzaseasonAreaged6monthsthrough18yearsandreceivinglongtermaspirintherapyandwhothereforemightbeatriskforexperiencingReye'ssyndromeafterinfluenzavirusinfectionAreresidentsofnursinghomesandotherchroniccarefacilitiesAreAmericanIndians/AlaskaNativesAremorbidlyobese(bodymassindexis40orgreater)ArehealthcarepersonnelArehouseholdcontactsandcaregiversofchildrenagedyoungerthan5yearsandadultsaged50yearsandolder,withparticularemphasisonvaccinatingcontactsofchildrenagedyoungerthan6monthsArehouseholdcontactsandcaregiversofpeoplewithmedicalconditionsthatputthemathigherriskforseverecomplicationsfrominfluenzaAsinpreviousrecommendations,allchildrenaged6monthsto8yearsofagewhoreceiveaseasonalinfluenzavaccineforthefirsttimeshouldreceivetwodoses.Childrenwhoreceivedonlyonedoseofaseasonalinfluenzavaccineinthefirstinfluenzaseasonshouldreceivetwodosesratherthanoneinthefollowinginfluenzaseason.Anewlyapprovedinactivatedtrivalentvaccinecontaining60mcgofhemagglutininantigenperinfluenzavaccinevirusstrain(FluzoneHighDose[SanofiPasteur])isanalternativeinactivatedvaccineforpeople65yearsofageandolder.

TheCDCoccasionallymakeschangesandupdatesitsinformationonvaccinesandotherrecommendationsaboutthecurrentflupandemic.TheCDCstates,"forthemostaccuratehealthinformation,visithttp://www.cdc.govorcall1800CDCINFO,24/7."Caregiversshouldcheckthevaccinepackageinsertsformoredetailedinformationonthevaccineswhentheybecomeavailable.

TheCDCsaysthatagoodwaytopreventanyfludiseaseistoavoidexposuretothevirusthisisdonebyfrequenthandwashing,nottouchingyourhandstoyourface(especiallythenoseandmouth),andavoidinganycloseproximitytoortouchinganypersonwhomayhaveflusymptoms.Sincetheviruscanremainviableandinfectiousforabout48hoursonmanysurfaces,goodhygieneandcleaningwithsoapandwateroralcoholbasedhanddisinfectantsarealsorecommended.Somephysicianssayfacemasksmayhelppreventgettingairbornefluviruses(forexample,fromacoughorsneeze),butothersthinkthebetteruseformaskswouldbeonthosepeoplewhohavesymptomsandsneezeorcough.

TheuseofTamifluorRelenzamayhelppreventthefluiftakenbeforesymptomsdeveloporreducesymptomsiftakenwithinabout48hoursaftersymptomsdevelop.Someinvestigatorssaythatadministrationofthesedrugsisstillusefulafter48hours,especiallyinhighriskpatientpopulations.However,takingthesedrugsisnotroutinelyrecommendedforpreventionforthehealthypopulationbecauseinvestigatorssuggestthatasoccurswithmostdrugs,flustrainswilldevelopresistancetothesemedications.DuringtheH1N1pandemic,theCDCmadefurthersuggestionsabouttheuseoftheseantiviralmedicationsanddevelopedtheinterimguidelinesforuseofTamifluandRelenzaasfollows,andthishasnotchangedforthe20142015fluseason:

1. Patientswithhighriskfactorsshoulddiscussflusymptomsandwhentouseantiviralmedicationsdoctorsshouldprovideaprescriptionfortheantiviraldrugforthepatienttouseifthepatientisexposedtofluordevelopsflulikesymptomswithouthavingtogointoseethedoctor.

2. "Watchfulwaiting"wasaddedasaresponsetotakingantiviralmedications,withtheemphasisonthefactthatthosepeoplewhodevelopfeverandhaveapreexistinghealth

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conditionshouldthenbegintheantiviralmedication.3. TheantiviralmedicationsarethefirstlinemedicinesfortreatmentofnovelH1N1,H3N2,and

H3N2vflu,andmostcasesaretodatesusceptibletoTamifluandRelenza.

Ingeneral,preventivemeasurestopreventthespreadoffluareoftenundertakenbythosepeoplewhohavesymptoms.Symptomaticpeopleshouldstayathome,avoidcrowds,andtakeofffromworkorschooluntilthediseaseisnolongertransmittable(abouttwotothreeweeks)oruntilmedicalhelpandadviceissought.Sneezing,coughing,andnasalsecretionsneedtobekeptawayfromotherpeoplesimplyusingtissuesanddisposingofthemwillhelpothers.Quarantiningpatientsisusuallynotwarranted,butsuchmeasuresdependontheseverityofthedisease.TheCDCrecommendsthatpeoplewhoappeartohaveaninfluenzalikeillnessuponarrivalatworkorschoolorbecomeillduringthedaybepromptlyseparatedfromotherpeopleandbeadvisedtogohomeuntilatleast24hoursaftertheyarefreeoffever(100F[37.8C]orgreater),orsignsofafever,withouttheuseoffeverreducingmedications.ThenovelH1N1swinefludiseasetakesaboutsevento10daysbeforefeversstop,butresearchdatasuggestswaitinguntilthecoughisgonesincemanypeoplearestillinfectiousaboutoneweekafterfeverisgone.However,theCDCdidnotextendtheirrecommendationstostayhomeforthatextraweek.

Canswineflubepreventediftheswinefluvaccine(orotherflustrainvaccines)isnotreadilyavailable?

Althoughvaccinationisthebestwaytopreventtheswineflu,theremaybetimesinthefuturewhenvaccinemaynotbeavailable.Currently,therearenoshortagesofthetrivalentfluvaccinethatcontainsH1N1antigens.However,duringthe2009H1N1pandemic,thissituationdidoccursopeoplewantedtoknowwhattheycoulddotoprotectthemselves.If,inthefuture,vaccinesuppliesdonotmeetdemands,therearesomethingspeoplecandototryandpreventinfection.Withoutvaccination,thebeststrategyistonotallowanyvirustypetocontactaperson'smucus.Quarantininganyvirusinfectedpeopleisanextrememeasurethatmayworkinsomeinstances(forexample,Chinausedthismethod),butevenwithquarantining,thevirusmaystillspreadbypeoplewhohaveminimalornosymptoms.

Thenextstep,thatiseasiertobeimplementedbyindividuals,isforpeoplewiththediseasetoselfquarantineuntiltheybecomenoninfectious(aboutsevento10daysafterflusymptomsabate).Infectedpeoplecanwearsurgicalmaskstoreducetheamountofdropletsprayfromcoughsandsneezesandthrowawaycontaminatedtissues.Unfortunately,theseapproachesdependonthecomplianceofmanyotherpeople,andthelikelihoodthatsuchmethodswillbehighlysuccessfulinpreventingfluvirusinfections,atbest,isonlyfair.Suchmethodsdidnotstopthe2009H1N1pandemic,althoughtheymayhavesomebenefitforafewindividuals.

Yettherearestillsomeothermethodsavailabletoindividuals.Perhapsthebestwayforindividualstotrytopreventfluvirusinfectionisacombinationofmethodsthatareaimedatfulfillingtheverybasicprinciplethatifthevirusdoesn'treachanindividual'smucusmembranecells,infectionwillbeprevented.Themethodsareasfollows:

1. Killorinactivatethevirusbeforeitreachesahumancellbyusingsoapandwatertocleanyourhandswashingclothingandtakingashowerwilldothesamefortherestofyourbody.

2. Useanalcoholbasedhandsanitizerifsoapandwaterarenotreadilyavailable,andusesanitizersonobjectsthatmanypeoplemaytouch(forexample,doorknobs,computerkeyboards,handrails,phones),althoughsomeresearcherssuggestthatsuchsanitizersaregenerallyineffective.

3. Donottouchyourmouth,eyes,nose,unlessyoufirstdoitems1or2above.4. Avoidcrowds,parties,andespeciallypeoplewhoarecoughingandsneezing(mostvirus

containingdropletsdonottravelmorethan4feet,soexpertssuggest6feetawayisagooddistancetostay).Ifyoucannotavoidcrowds(orparties),trytoremainawareofpeoplearoundyouandusethe6footrulewithanyonecoughingorsneezing.Donotreachfororeatsnacksoutofcanistersorothercontainersatparties.

5. Avoidtouchinganythingwithinabout6feetofanuncoveredcough/sneeze,becausethedropletsthatcontainvirusfallandlandonanythingusuallywithinthatrange.

6. StudiesshowthatindividualswhowearsurgicalorN95particlemasksmaypreventinhalationofsomeH1N1virus,butthemasksmaypreventonlyabout50%ofairborneexposuresandoffernoprotectionagainstsurfacedroplets.However,masksonH1N1infectedpeoplecanmarkedlyreducethespreadofinfecteddroplets.

ThesesixstepscanhelppreventindividualsfromgettingH1N1andothertypesofinfection,butformanypeople,adherencetothemmaybedifficultatbest.However,therearesomeadditionalstrategiesthatmayalsohelppreventviralinfectionsinunvaccinatedpeopleaccordingtosomeinvestigators.Salinenasalwashesandgarglingwithsaline(oracommercialproduct)asawaytoreduceoreliminateviralvirusfrommucusmembraneshasbeensuggested.Proponentsofthesemethodsbasetheirrationaleonthefactthatfluvirusesusuallytakeabouttwotothreedaystoproliferateinnasal/throatcells.Whilenasalwashesand

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garglingmaybesoothingtosomepeople,therearenostudiesthatindicateH1N1orothervirusesarekilled,inactivated,orcompletelyremovedbythesemethodsconversely,therearenodatasuggestingthesemethodscannothaveanyeffectonH1N1.However,withlongtermnasalwashesusingNetipots,sinusinfectionwithotherpathogensmaybeencouraged.

OtherinvestigatorsandphysicianshaveofferedadditionalmethodsthatmayhelpreduceexposuretoH1N1virus.Forexample,Dr.Gerberding,aformerCDCdirector,hadseveralsuggestionsabouthowtoavoidH1N1infectiononanairplane.Shesuggestedthefollowing:

1. Ifapersonisnexttoyouornear(within6feet)andiscoughing/sneezing,asktheflightattendanttoofferthepersonamask.

2. Ifthereareavailableseats6feetormoreawayfromthecoughing/sneezingperson,asktochangeyourseat(planesaregoodmeansoftravelbecausetheairisrecirculatedthroughHEPAfiltersthatcancaptureviruses,buteventhefilterswillnothelpifpeopletouchareaswheredropletshavelandedHEPAfiltersareusuallynotavailableinbuses,cars,ships,ortrains).

3. Turnawayfromthecoughing/sneezingpersonandturntheairventtowardthepersontoblowthedropletsawayfromyourself.

Variationsofhersuggestionsmaybeapplicableinmanydifferentsocialorwork,ortravelsituations,buttherearenodatatoprovethesemethodsareeffective.Inaddition,commonsenseprecautionssuchasnotdrinkingoreatingthingstouchedbyothers,avoidingcasualphysicalcontacts(forexample,handshakes,socialhugsorkisses,publicwaterfountains[theseareOKifyoutouchnothingandlipsonlytouchflowingwater],banistersonstairways,andrestroomdoorhandles)willlimitexposuretoH1N1andotherviruses.Again,thesecommonsensesuggestionslackdatasubstantiation.

Manyinvestigatorssuggestthatpeoplestaywellhydrated,takevitamins,andgetplentyofrest,buttheseprecautionswillnotpreventH1N1orotherviralinfections,althoughtheymayhelpreducetheeffectsofinfectionbystrengtheningtheperson'simmunesystemtofightinfection.Similarly,currentantiviralmedications(describedintheprecedingsection)actonH1N1andothervirusesthathavealreadyinfectedcellstheyworkbypreventingorreducingviralparticlesfromaggregatingandbeingreleasedfrominfectedcells.Timingisimportantifonlyafewcellsareinfectedandtheantiviralmedicationsareadministeredquickly(usuallybeforeflusymptomsdeveloporwithin48hours),thevirusesarereducedinnumber(theycannoteasilybudoutfromthecellsurface),sofew,ifany,otherrespiratoryormucusmembranecellsbecomeinfected.Thiscanresultineithernoflusymptomsor,ifalargernumberofcellswereinitiallyinfected,lessseveresymptoms.TheoveralleffectforthepersonisthattheH1N1orotherviralinfectionwasprevented(itwasnotthesymptomswerepreventedfromdeveloping)orthatsymptomswerereduced.

Therearemanyflu"cures"and"treatments"listedintheInternet(forexample,howcayennepeppercanbeusedtotreattheflu)beforeusinganyofthesesubstances,checkwithyourdoctor.

Inthestrictestsenseofthewordprevention,eveneffectivevaccinesdonot"prevent"infections.Whattheydoaccomplishistoalerttheimmunesystemtobeonguardforcertainantigensthatareassociatedwithaspecificdiseasecausingagent(forexample,H1N1virus,pneumococcalbacteria).Whentheagentfirstinfectsthehost,itsantigensarerecognized,andthesecausearapidimmuneresponsetooccurthatpreventsthepathogenfromspreadinganddevelopingsymptomsinthehost.People,includingphysiciansandresearchers,oftentermthiscomplexresponsetovaccinationas"preventionofinfection,"butwhatactuallyoccursisthepreventionoffurtherinfectionsowellthatsymptomsdonotdeveloporareminimalinthehost.

Insummary,ifH1N1orothervirusesfailtocontactcellstheycaninfect,thediseasewillbeprevented.Asstatedabove,thisisdifficult,butnotimpossible,todoinalmostallsocieties.Preventionofflusymptomsofinfectionispossiblewithantiviralmedicationsifthesearegivenveryearlyintheinfection.Therearemanyothermethodsthatmayreducethechanceofgettingthevirusonaperson'smucosalsurface,butmostmethodshavenotbeenbackedupwithobjectivedata.MostdoctorsandinvestigatorssuggestthatitemsthathelpboostorallowtheimmuneresponsetofunctionwellwillhelppeopleresistH1N1andotherviralinfectionsandreducesymptoms,butthesealsodonotpreventinfections.Consequently,whilewaitingforaspecificantiviralvaccinetobedevelopedorbecomeavailable,therearesomewaysindividualscanimprovetheirchancesofpreventingorreducingthesymptomsoffluvirusinfections.AllofthesesuggestionsapplytoH3N2vcausedswinefluaswell.BecauseH3N2vfluhasbeenmorecloselyrelatedtopigs,pigfarmingandcountyfairs,peoplewhoareathigherrisk(seeabove)shouldavoidcontactingpigsinthesesettings.

Wasswineflu(H1N1)acauseofanepidemicorpandemicinthe20092010fluseason?

Yes.Anepidemicisdefinedasanoutbreakofacontagiousdiseasethatisrapidandwidespread,affectingmanyindividualsatthesametime.TheswinefluoutbreakinMexicofitthisdefinition.Apandemicisan

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epidemicthatbecomessowidespreadthatitaffectsaregion,continent,ortheworld.OnJune11,2009,WHOofficialsdeterminedthatH1N12009influenzaAswineflureachedWHOlevel6criteria(persontopersontransmissionintwoseparateWHOdeterminedworldregions)anddeclaredthefirstflupandemicin41years.TheH1N1flureachedover200differentcountriesoneverycontinentexceptAntarcticainthe20092010fluseasonfortunately,theseverityofthediseasedidnotincrease.ThefollowingistheCDCdataformortalityandmorbidityofthe2009epidemicintheUS:finalestimateswerepublishedin2011andstatethatfromApr.12,2009,toApr.10,2010approximately60.8millioncases(range:43.389.3million),274,304hospitalizations(195,086402,719),and12,469deaths(886818,306)occurredintheUnitedStatesduetoH1N1.

Whatistheprognosis(outlook)andcomplicationsforpatientswhogetswineflu?

Ingeneral,themajority(about90%95%)ofpeoplewhogetthediseasefeelterrible(seesymptoms)butrecoverwithnoproblems,asseeninpatientsinMexico,theU.S.,andmanyothercountries.

Peoplewithsuppressedimmunesystemshistoricallyhaveworseoutcomesthanuncompromisedindividualsinvestigatorssuspectthatasswinefluspreads,themortalityratesmayriseandbehighinthispopulation.Currentdatasuggestthatpregnantindividuals,childrenunder2yearsofage,youngadults,andindividualswithanyimmunecompromiseordebilitationarelikelytohaveaworseprognosis.ComplicationsofswineflumayresemblesevereviralpneumoniaortheSARS(severeacuterespiratorysyndromecausedbyacoronavirusstrain)outbreakin20022003inwhichthediseasespreadtoabout10countrieswithover7,000cases,causedover700deaths,andhada10%mortalityrate.Atthebeginningofthepandemic,thenumbersofpeoplewithflulikeillnesswerehigherthanusualandtheillnessinitiallyaffectedamuchyoungerpopulationthantheconventionalflu.Asthepandemicprogressed,moreyoungchildrenbecameinfectedthanusual,butthemortalitystatisticsbecamemoresimilartotheconventionalflumortalityrate,withanolderpopulation(especiallyages5064)havingthehighestdeathrate.Pneumonia(viralandsecondarybacterialpneumonia),isthemostseriouscomplicationofthefluasitcancausedeath.Othercomplicationsincludesinusandearinfections,asthmaexacerbations,and/orbronchitis.

Whatisthelatestnewsaboutswineflu?

Feb.2,2015:TheBBCreportedthatoverthelastsixweeks,atleast75peopleinIndiahavediedfromswineflu(H1N1).Althoughdeathshavenotreachedthelevelsseenin2012(405)or2013(692),thereisconcernthatbecauseIndiaishavingacolderthannormalwinter(coldestinthelast20years),thenumberofdeathsmayincreasebeforethefluseasonabates.Inaddition,IndianhealthofficialsareinvestigatingiftheH1N1virushasdevelopeda"minormutation."However,theyindicateH1N1infectedpatientsarerespondingtocurrentmedicines.

Jan.26,2015:InNewDelhi,India,another18peoplehavetestedpositiveforH1N1swinefluvirus.Thisbringsthetotalnumberofpeoplediagnosedto179,withthreedeaths.However,officialssuggestthatthereisnoneedforalarmastheyexpectthenumberofinfectedpeopletorapidlydeclineasthewarmerweatherbeginstooccur.NewDelhihospitals(22hospitals)claimthereareenoughmedicinesinstocktotreatindividualshospitalizedwithswineflu(H1N1).

Jan.20,2015:TheH1N1virus,commonlyknownastheswinefluvirus,hasbeguntocauseconcerninIndiathisyear.SinceJan.1,2015,over150swinefluinfectionshavebeenreported,alongwithsevendeathsinIndia.InDec.2014,positivecasesofswinefluwerefirstreported.Telangana,astateinthesouthernregionofIndia,hasreportedthemostcasesofH1N1(over120).Currently,10otherstatesinIndiahavereportedH1N1infectionswithafewdeaths.BecauseIndiahassuchadensepopulationandsinceH1N1canbespreadthroughtheairviadroplets,theIndianHealthMinistryhasaskedtheirstateofficialstoensuresanitationandhygieneinallpublicplacesandtobringaboutawarenesstopeopleaboutthesymptomsofswineflu.TheconcernisthatrisingnumbersofswinefluinfectionsmaybethebeginningofanotherH1N1epidemic,althoughthecurrentstrainmaynotbeasdeadlyasthe2009H1N1strain.

WherecanIfindmoreinformationaboutswineflu(H1N1andH3N2v)?

Foradditionalinformationseethefollowing:

"SeasonalInfluenza(Flu),"CDC

"PregnantWomen&Influenza(Flu),"CDC

"InfluenzaA(H3N2)VariantVirus,"CDC

REFERENCES:

2/6/2015 SwineFlu:ReadAboutSymptoms,TreatmentandH1N1Vaccine

http://www.medicinenet.com/script/main/art.asp?articlekey=99529&pf=2 10/10

UnitedStates.CentersforDiseaseControlandPrevention."Influenza(Flu)."Nov.24,2014..

UnitedStates.Flu.gov."H1N1.".

MedicallyReviewedbyaDoctoron2/2/2015

2015MedicineNet,Inc.Allrightsreserved.MedicineNetdoesnotprovidemedicaladvice,diagnosisortreatment.Seeadditionalinformation

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