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Influenza (Symptoms (Sudden onset, Headache, Chills, Fever, High mortality…
Influenza
Symptoms
Sudden onset
Headache
Chills
Fever
High mortality in very young and elderly
Flu
About Virus
Three types
Influenza A
Influenza B
Influenza C
Orthomyxovirus
-ssRNA
Can be found in other species
Especially A
Enveloped
Haemagglutinin and Neuraminidase - major surface antigens/virulence factors
Influenza A
Neuraminidase
N1-N9
Weak Neutralising Antibody
Haemagglutinin
H1-H16
Strong neutralising Ab response
Has 5 major antigen recognition sites
Lots of variation
Hypothesise that people will have bias immune responses to diff epitopes causing evolutionary change of the virus at these points
Means virus will be slightly different when passed on
Shown to be true in rabbits
Doesn't support annual epidemics as drift takes ~4 yrs
Todays isolates have a low relatedness to viruses from ~50yrs ago
Human Epidemiology
Epidemics
Around winter
Varying scale
Climate
Temperate
Seasonal peaks in winter
Tropical
Low year round levels
Caused by antigenic
DRIFT
Evolution
Different virus isotopes can dominate annual epidemics
Doesn't have to be the same in each hemisphere
Pandemics
Sporadic occurrence
Outside of seasonal peaks
Caused by antigenic
SHIFT
Reassortment events
Usually zoonotic transmission
Control
Vaccines
Subcutaneous
No mucosal immunity/T-cell immunity
65yrs
Twice yearly reformulated
Not long lasting becuase of shift
70% efficacy
Comparatively not great
Killed virus
Last UK - H3N2
Quadravalent
Must have two InlfuB
Nasal spray for chilldren
Low efficacy in USA therefor recalled
Therapy
Combination
2 ion channel inhibitors InfluA
Rimantidine
Neuraminidase inhibitors InfluA&B
Zanamivir
Characterised by a respiratory tract infection in humans