高中英语Unit9 Health care文章 What is Bird Flu人教版第三册VIP专享VIP免费

WhatisBirdFluHerearesomekeyquestionsandfactsaboutbirdflu.WHATISBIRDFLU?*Avianinfluenzaisaninfectiousdiseaseofbirdscausedbystrainsoftheinfluenzavirus.Thedisease,whichwasfirstidentifiedinItalymorethan100yearsago,occursworldwide.*Allbirdsarethoughttobesusceptibletoinfectionwithavianinfluenza,thoughsomespeciesaremoreresistantthanothers.*Infectioncausesawidespectrumofsymptomsinbirds,rangingfrommildillnesstoahighlycontagiousandrapidlyfataldiseaseresultinginsevereepidemics.Thelatterisknownas"highlypathogenicavianinfluenza".Thisformischaracterizedbysuddenonset,severeillness,andrapiddeath,withamortalitythatcanapproach100percent.*Fifteensub-typesofinfluenzavirusareknowntoinfectbirds,thusprovidinganextensivereservoirofinfluenzavirusespotentiallycirculatinginbirdpopulations.ISBIRDFLUHARMFULTOHUMANS?*Humanfatalitiesfromavianinfluenzawereunknownbefore1997,whensixpeopleinHongKongdiedafterbeinginfectedwiththeH5N1strainofthedisease.ButthedestructionofHongKong'sentirepoultrypopulation--around1.5millionbirds--withinthreedays,reducedopportunitiesforfurtherdirecttransmissiontohumans,andmayhaveavertedapandemic.*InApril2003,aDutchveterinarianwhohadbeenworkingonafarminfectedwithbirdflubecameillwithanH7strainofthediseaseanddiedofpneumonia.Thevetdidnottakemedicationagainstavianandhumanflu.HUMANCASUALTIESFROMBIRDFLU用心爱心专心*37Vietnamesehavediedsincelate2003.Thediseasehasalsokilled12ThaisandfourCambodians.COULDBIRDFLUBECOMEAHUMANEPIDEMIC?*Althoughavianfluisveryinfectiousinbirds,itdoesnotspreadeasilyamonghumans.Thereisadanger,however,thatanavianvirusmixeswithahumanoneandformsanewdisease.*Thenewviruscouldsharegeneticmaterialfrombothviruses,beinghighlyinfectiouslikehumanfluanddangerouslyfatalliketheavianvariety.*AccordingtoaWHOreportearlierinMay,thespateofhumanbirdflucasesinVietnamthisyearsuggestedthedeadlyvirusmaybemutatinginwaysthataremakingitmorecapableofbeingpassedbetweenhumans.--ThefindingpointstothegreatestfearofhealthexpertsthattheH5N1viruscouldunleashapandemicandkillmillionsaroundtheglobeifeveritgainedtheabilitytobetransmittedamonghumansefficiently.*Newinfluenzastrainshavecausedpandemics,mostrecentlyin1956-1957and1967-1968,killingacombined4.5millionpeople用心爱心专心