Influenza virus causes new epidemic by (3-5 yrs) -: (A) Antigenic drift, (B) Antigenic shift, (C) Cyclic trends, (D) Mosaicsm
Answer is B. Antigenic variations in Influenza Antigenic shift Antigenic drift Occurs due to Genetic recombination/reassoment / Rearrangement Point mutation Nature Sudden Gradual / insidious May lead to Epidemics/ pandemics Sporadic cases Ref: Park 25th edition Pgno : 166-172