Not true regarding influenza virus is -: (A) All types exhibit antigenic shift, (B) Onlybtype A shows antigenic drift, (C) Drift is accumulation of point mutations, (D) None of the above
Answer is A. Antigenic drift the gradual sequential change in antigenic structure occurring regularly at frequent intervals. Antigenic drift is due to mutation and selection. It accounts for the periodic epidemics of influenza. REF:ANANTHANARAYAN AND PANIKER'S TEXTBOOK OF MICROBIOLOGY 9TH EDITION PAGE NO-499