Recurrent Influenza Due to Viral and Immune Factors

Steps:

• Evaluate statement 1: Influenza viruses mutate, altering antigens (antigenic drift/shift), evading prior immunity.
• Evaluate statement 2: Weak immunity produces fewer B-memory cells, reducing long-term antibody response to the virus.
• Evaluate statement 3: Untreated HIV depletes T-helper cells, impairing overall immune coordination against influenza.
• Combine: All three explain reinfection by bypassing or weakening adaptive immunity.

Why A is correct:

• All statements align with immunology principles: antigenic variation and immune deficiencies allow reinfection, as memory responses fail.

Why the others are wrong:

• B omits immune weaknesses in 2 and 3, ignoring non-viral reinfection causes.
• C excludes 2, missing how poor B-cell memory enables repeat infections independently of HIV.
• D ignores 1, the primary reason for influenza's annual epidemics via mutation.

Final answer: A