HL A2.2 Rapid Virus Evolution

Viruses evolve rapidly due to high mutation rates, short generation times, and large population sizes.

Antigenic drift involves small, gradual mutations in viral surface proteins that reduce immune recognition.

RNA viruses lack error-checking enzymes during replication, leading to frequent mutations.

Influenza A undergoes both drift and shift, making vaccines short-lived and pandemics possible.

Antigenic shift occurs when two viral strains infect the same cell and reassort genes, forming a new subtype.

HIV evolves rapidly due to reverse transcriptase errors, short generation time, and high replication rate.

Rapid evolution leads to vaccine difficulty, immune evasion, and drug resistance.