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What is Not true regarding influenza virus is -a) All types exhibit antigenic shiftb) Only type A shows antigenic driftc) Drift is accumulation of point mutationsd) None of the above and explain in detail?
Antigenic shift is seen only in Influenza 'A' virus.
Antigenic drift is seen in Influenza A and B.
Antigenic drift involves "point mutation" in the gene owing to selection pressure by immunity in the host population.
Influenza shows cyclic trend due to these antigenic variations
Type A epidemics every 2-3 years
Type B epidemics every 4-7 years
Type A pandemics every 10-15 years