False about antigenic drift -
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
Occur under pressure for immunity
Responsible for epidemics of influenza
Occurs only in influenza-A
Occur every 10-12 years
Virology