This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
[{'content': 'Influenza pandemic is due to \nSelect and explain. \nA. Antigenic shift, B. Antigenic drift, C. Different strains, D. All', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. a (Antigenic shift). (Ref. Anantanarayan, Microbiology, 4th/pg.487)TermCommentsAntigenic drift- Gradual sequential change at frequent interval i.e. mutation of pathogen (e.g. Influenza A), such that the surface antigens differ from those of previously existing strains.- Accounts for small epidemics.Antigenic shift- Sudden drastic discontinuous change in antigenic structure i.e., by recombinant DNMA technology. - Accounts for major epidemic and pandemics.', 'role': 'assistant'}]