Not true regarding influenza virus is -
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
All types exhibit antigenic shift
Onlybtype A shows antigenic drift
Drift is accumulation of point mutations
None of the above
Virology