A public health officer investigating an influenza outbreak notes that a new pandemic strain has emerged by combining gene segments from two different influenza A strains infecting the same host cell. This mechanism of generating new influenza strains with novel surface antigens is called:
- A Antigenic drift
- B Antigenic shift ✓
- C Phenotypic mixing
- D Pseudoreversion
Correct answer: B. Antigenic shift
Explanation
Antigenic shift refers to the sudden, major change in influenza A surface antigens (hemagglutinin and/or neuraminidase) due to reassortment of genomic RNA segments when two different influenza A strains co-infect the same cell — producing a novel subtype that can cause pandemics due to lack of pre-existing population immunity. Antigenic drift is the gradual accumulation of point mutations in HA/NA causing minor changes and seasonal epidemics. Phenotypic mixing involves exchange of surface proteins without genomic change.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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