Theinfectionwithparainfluenzavirusesisanair-borneinfectionandappearsendemicallyworldwide.TheSEROprevalenceofparainfluenzaininfantsintheirfirstyearoflifeis50%.Typicalforparainfluenzavirusesarefrequentreinfections,characteristicallyforparainfluenza3.Incubationtimeis2-6days.Theparainfluenzavirusesareasubgroupoftheparamyxoviruses.Togetherwiththerespiratorysyncytialviruses(RSviruses),thepathogensbelongtothemajorviralpathogensofdiseasesoftherespiratorytract,accompaniedbysevereclinicalsymptoms.Inadults,parainfluenzaviruscausesafeverishrhinitisandlaryngitis.Firstsignsaresuddenheadaches,paininmusclesandjoints,followedbyfeverof38°-39°C.Ifthelowerrespiratorytractisinvolved,additionallytrachyphoneaanddrycoughdevelopsasasignoftracheobronchitis.
Parainfluenza1causesseverepneumoniasinnewborns,manifestedbyhighfever,cyanosis,dyspnoeaandbloodypurulentsputum.Sometimes,meningitissymptomsoccuratthesametime.Parainfluenza2veryoftencausesanacutelaryngotracheobronchitiswithpseudocroupininfantsandchildren.Firstsignsoftheinfectionarecatarrhalsymptomsfollowedbytrachyphoena,drybarkingcoughandinspiratorystridor.Parainfluenza3virusesareconsideredasthemajorpathogensofpneumoniaandbronchiolitis.Whiletypes1,2and3aredistributedworldwide,parainfluenzatype4appearsonlyintheUSA.Infections1and3occuralltheyear,whileparainfluenza2and4virusesappearonlysporADIcally.
Laboratorydiagnosisofparainfluenzavirusesisdoneusinghaemagglutination-inhibitingtest(HIT)complementbindingreaction(CF)andneutralisationtest(NT).NewermethodsareIFAandELISA,whichallowidentifyingIgGandIgAantibodiesinthepatientserum.Indifferentialdiagnosis,testsforotherparamyxoviruseslikemumps,shippingfevervirusesandsimianvirustype5havetobeperformedduetopossIBLecross-reactions.