Influenza Virus Flashcards
Influenza is an
Orthomyxo (-RNA) virus
Influenza A, B, C
Enveloped, single strand RNA virus
Frequent genetic reassortment
Influenza surface antigens
Hemagglutinin (HA)
Binds sialic acid cell receptors on epithelial cells
Promotes fusion
Hemagglutinates red blood cells (binds and aggregates)
Neuraminidase (NA
Cleaves terminal sialic acid allowing release from infected cells
Influenza life cycle
Virus attachment
Hemmaglutinin binds sialic acid
Enters via recepter mediated endocytosis
Viral envelope fuses with endosome and releases content
Influenza A has M2 proteins to facilitat
Genetic material travels to nuclease and -RNA converted to + RNA
Bud off via neurominidase cleaving sialic acid
Influenza A vs B
A: respiratory infections, recombines, affects many species
B: affect adoscents and school age children, myosistits and gastointestinal symptoms
Antigenic drift
HA>NA
Gradual point mutations at antigenic sites
Influenza A»B
Antigenic shift
Genetic reassortment resulting in changing HA or NA type
“New virus”
Occurs only in influenza A
Nomenclature
Antigenic type (A or B)/host of origin/geographical origin/strain number/year of isolation/ H/A antigen type (if influenza A)
Symptoms of Influenza
headache
fver
runny nose
sore throat
body aches
muscular fatigue
joint aches
coughing
vomiting
Influenza complications
respiratory failure
bacterial pneumonia
myositis
encephalilis, gullain-barre syndrome
myocarditis
maternal and infant mortality/morbidity
Influenza transmission
droplets, fomites
Factors promoting rapid spread during influenza season
rapid replication peak shedding in first 3 days
short incubation (2 days)
Influenza diagnosis
clinical presentation
molecular assays (PCR)
Antigen detection
viral culture (not used for additional testing)
Influenza prevention
vaccination
avoid contact
chemoprophylaxis
vaccines contain
2 influenza A and 1-2 influenza B strains
best way to stop spread of influenza
antivirals
