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GastrointestinalVirusesViralGastroenteritisItisthoughtthatvirusesareresponsibleforupto3/4ofallinfectivediarrhoeas.Viralgastroenteritisisthesecondmostcommonviralillnessafterupperrespiratorytractinfection.Indevelopingcountries,viralgastroenteritisisamajorkillerofinfantswhoareundernourished.Rotavirusesareresponsibleforhalfamilliondeathsayear.Manydifferenttypesofvirusesarefoundinthegutbutonlysomeareassociatedwithgastroenteritis.
AssociatedwithgastroenteritisRotavirusesAdenoviruses4041Caliciviruses嵌杯病毒NorwalklikevirusesorSRSV(SmallRoundStructuredViruses)AstrovirusesSRV(SmallRoundViruses)CoronavirusesTorovirusesFoundinthegutasopportunisticinfectionCMVHSVVZVHIVGastrointestinalVirusesVirusGenomeTypicaldiseaseincubationDurationRotaviruses:GroupA,B,Cds-segmentedRNAMajorcauseofdiarrheainchildren1-3days24-56h5-8days3-7daysCalicivirusesNorwalkagentsssRNAInfectsadultsandchildrenEpidemicviralgastroenteritis1-3days18-24h1-3days12-48hEAd40,41LineardsRNAdiarrheainchildren7-8days8-12dAstrovirus+ssRNAInfectsmainlychildrenandelderly1-4days1-4dGastrointestinalVirusesInfants:RotavirusA;Adenovirus40,41;CoxsackieA24virusInfants,children,andadultsNorwalkvirus;Calicivirus嵌杯病毒;astrovirus;RotavirusB;Reovirus.ImportantCharacteristics70nmround,doubleshelled,enclosingagenomeof11segmentsofdoublestrandedRNA.GroupsofRotavirusesGroupAsubtypes1,2,3,4(mainhumanpathogens)
(Further7subtypes)alsoinfectanimals(monkey,calf,mouse)GroupBInfectspigsandrats
FoundtocauseextensiveoutbreaksinChinainpastdecadeGroupCInfectsPigs(OccasionallyMan)GroupDInfectsbirdsGroupEInfectspigsPathogenesisEssentiallyaningestiondisease(faecal-oralroute)Incubationisshort:1to3daysIllness:Suddenonsetwaterydiarrhoea,withorwithoutvomiting.Maylastupto6days(orlongerifimmunocompromised).Thediseaseisselflimiting.Complications:Dehydrationmayresult,thiscanbesevereandlifethreateninginyoungchildren.PathogenesisGroupA:MainpathogenofinfantilediarrheaGroupB:CauseepidemicadultdiarrheaGroupC:CausehumanoranimalsporadicdiarrheaTreatmenttreatmentofdehydrationbyoraland/orintravenousfluidsandelectrolytesPreventionNonspecificfactors:improvedhygiene,education,cleanwater
Specific-Breastfeedinghelpstoprovidepassiveimmunityinthenewborn(frommaternalantibodies),
Vaccinationisstillexperimental.EntericAdenovirusesNakedDNAviruses,75nmindiameter.Fastidiousentericadenovirustypes40and41areassociatedwithgastroenteritis.Associatedwithcasesofendemicgastroenteritis,usuallyinyoungchildrenandneonates.Cancauseoccasionaloutbreaks.Possiblythesecondmostcommonviralcauseofgastroenteritis(7-15%ofallendemiccases).SimilardiseasetorotavirusesMostpeoplehaveantibodiesagainstentericadenovirusesbytheageofthree.DiagnosedbyelectronmicroscopyorbythedetectionofadenovirusantigensinfaecesbyELISAorotherassays.CalicivirusesSmallRNAviruses,characteristicsurfacemorphologyconsistingofhollows.particles35nmindiameter.Associatedmainlywithepidemicoutbreaksofgastroenteritis,althoughoccasionallyresponsibleforendemiccases.LikeNorwalktypeviruses,vomitingistheprominentfeatureofdisease.Majorityofchildrenhaveantibodiesagainstcalicivirusesbytheageofthree.Diagnosedbyelectronmicroscopyonly,oftendifficulttodiagnosebecauseofsmallsize.Norwalk-like
VirusesSmallRNAviruses,withraggedsurface,35nmindiameter,nowclassifiedascaliciviruses.Alwaysassociatedwithepidemicoutbreaksofgastroenteritis,adultsmorecommonlyaffectedthanchildren.Associatedwithconsumptionofshellfishandothercontaminatedfoods.Aerosolspreadpossibleaswellasfaecal-oralspread.Alsonamed"wintervomitingdisease",withvomitingbeingtheprominentsymptom,diarrhoeausuallymild.Antibodiesacquiredlaterinlife,intheUS,only50%ofadultsareseropositivebytheageof50.DiagnosisismadebyelectronmicroscopyandbyPCR.GastrointestinalVirusesVirusGenomeTypicaldiseaseincubationDurationRotaviruses:GroupA,B,Cds-segmentedRNAMajorcauseofdiarrheainchildren1-3days24-56h5-8days3-7daysCalicivirusesNorwalk
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