B: Antigenic shift

Wed, 06 May 2026 17:13:45 +0000

# Understanding Antigenic Shift: A Key Mechanism in Influenza Virus Evolution Antigenic shift is a critical biological process that drives the evolution and spread of influenza viruses, posing ongoing challenges to global public health. Unlike gradual changes in viral traits—known as antigenic drift—antigenic shift involves sudden, major changes in the virus’s surface proteins, leading to new virus subtypes capable of triggering pandemics. This article explores what antigenic shift is, how it occurs, and why it matters in virology and pandemic preparedness. ### What Is Antigenic Shift? Antigenic shift refers to the abrupt change in influenza virus antigens—specifically the hemagglutinin (HA) and neuraminidase (NA) proteins—resulting from genetic reassortment between two or more different influenza virus strains. These surface proteins are key targets for the human immune system, so when their structure changes dramatically, previously acquired immunity offers little protection, increasing the risk of widespread infection.