Medical Microbiology

RNAviruses 459

Continued:StructureandReplication

Thecloseassociationofcellularandviraltranscriptionisalsoreflectedinthefact

thatRNAsynthesisinthemyxovirusestakesplaceinthenucleusofthehostcelland

not,asinotherRNAviruses,inthecytoplasm.

Pathogenesisandclinicalpicture.Theaerogenicallytransmittedinfluenza

virusesnormallyreplicateinthemucosaofthenasopharynx,resultingin

apharyngitisoratmostatracheobronchitis,afteranincubationperiodof

24 – 72 hours.Pulmonarydisseminationoftheinfectioncanresultfroman

upperrespiratoryinfectionormanifestwithoutone,wherebytheprognosis

inthelattercaseislessfavorable.Pneumoniacausedsolelybytheinfluenza

virusisrare.Asarule,bacterialsuperinfectionswithstaphylococci,strepto-

cocci,pneumococci,orHaemophilusbacteriaareresponsible.Theseinfec-

tions,whichusedtobethenormalcauseofinfluenzadeaths(Haemophilus

influenzaeinthe“Spanishflu”of 191 8),canbecontrolledwithantibiotics.

Diagnosis.Influenzavirusescanbegrownandisolatedincellculturesifthe

diagnosticspecimenisobtainedveryearly,i.e.,inthefirstoneortwodaysof

theinfection.Throatlavagesandswabsprovidesuitablematerial.Thelatter

mustbeplacedinasuitabletransportmediumwithoutdelaytopreventthem

fromdryingout.Identificationoftheculturedvirusesisachievedbasedon

thehemagglutinatingpropertiesofthemyxovirusesinthehemagglutination

inhibitiontestorbymeansofimmunofluorescence.

Ifthespecimenwasobtainedtoolateforvirusisolation,adiagnosiscanbe

arrivedatbyserologicalmeans,wherebyariseintheantibodytiterofpatient

serumprovesinfection.

Table8. 5 ClassificationandAntigenStructureofInfluenzaAViruses

Viralprototype Predominance Antigenformula

Hemagglutinin

(H)

Neuraminidase

(N)

A/WS/33

A/PR8/34

1932 – 1946 HO N1

A/Cambridge/46

A/F/M1/4 7

1946 – 1957 H1 N1

A/Singapore/5 7 1957 – 1968 H2 N2

A/HongKong/68 1968 H3 N2

A/USSR/7 7 1977 H1 N1

8

Kayser, Medical Microbiology © 2005 Thieme