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OrthomyxoviridaeOrthomyxoviridaeInfluenza VirusInfluenza Virus
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Properties Properties • Spherical Virion ( polymorphic) Spherical Virion ( polymorphic) • 100 nm Size100 nm Size• Segmented –SS-RNA : 7-8 segmentsSegmented –SS-RNA : 7-8 segments• Mostly segment: 1 protein and two Mostly segment: 1 protein and two
segment 2 proteinsegment 2 protein• H & N : Antigenic variationH & N : Antigenic variation• Resistant to room temperature and Resistant to room temperature and
spatially 4ºCspatially 4ºC
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Neuraminidase Neuraminidase helps the virus to release itself from the cells
HemagglutininHemagglutininHemagglutinin allows the virus to bind to host cells
RNARNA
Influenza Surface ProteinsInfluenza Surface Proteins
MM22 protein protein (only on type A)(only on type A)
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Clinically Relevant Influenza Clinically Relevant Influenza VirusesVirusesType AType A Potentially severe illnessPotentially severe illness
Epidemics and pandemicsEpidemics and pandemicsRapidly changingRapidly changing
Type BType B Usually less severe illnessUsually less severe illnessEpidemicsEpidemicsGenetically more stableGenetically more stable
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SubtypeSubtype HumanHuman SwineSwine HorseHorse BirdBirdH1H1H2H2H3H3H4H4H5H5H6H6H7H7H8H8H9H9H10H10H11H11H12H12H13H13H14H14H15H15
Hemagglutinin Subtypes of Hemagglutinin Subtypes of Influenza A VirusInfluenza A Virus
Adapted from Levine AJ. Viruses. 1992;165, with permission.
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SubtypeSubtype HumanHuman SwineSwine HorseHorseBirdBirdN1N1N2N2N3N3N4N4N5N5N6N6N7N7N8N8N9N9
Neuraminidase Subtypes of Neuraminidase Subtypes of Influenza A VirusInfluenza A Virus
Adapted from Levine AJ. Viruses. 1992;165, with permission.
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Influenza A Virus Constantly Influenza A Virus Constantly ChangesChanges Antigenic driftAntigenic drift
Small changes in H or N proteins that occur Small changes in H or N proteins that occur from year to yearfrom year to year
Antigenic shiftAntigenic shift Acquisition of new H or N protein, possibly from Acquisition of new H or N protein, possibly from
an bird virusan bird virus
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Diseases : Diseases : 1- Influenza:Signs and Symptoms1- Influenza:Signs and Symptoms Abrupt onset of symptomsAbrupt onset of symptoms FeverFever Cough with little or no sputumCough with little or no sputum HeadacheHeadache Muscle achesMuscle aches Sore throatSore throat light sensitivity, and eye painlight sensitivity, and eye pain
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• PneumoniaPneumoniaElderly, pregnant, and …..Elderly, pregnant, and …..Viral (1:3), most viral & bacterial Viral (1:3), most viral & bacterial
(S.areuse) (2:3)(S.areuse) (2:3)• Reye Syndrome:Reye Syndrome: encephalopathy in encephalopathy in
children (2-16 years) , mortality 10-40% , children (2-16 years) , mortality 10-40% , Influenza A & B, chicken pox ,Influenza A & B, chicken pox ,Salicylic acid compound Salicylic acid compound
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Immunity to influenzaImmunity to influenza• PermanatPermanat• Type Related Type Related • Antibody again H & NAntibody again H & N
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Treatment Treatment • Amantadine Amantadine • RimantadineRimantadinePreventionPrevention• Vaccination ( 70%)Vaccination ( 70%) Most effective in young, healthy Most effective in young, healthy
peoplepeople Less effective in the elderlyLess effective in the elderly
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Influenza Virus VaccineInfluenza Virus Vaccine