A 35-year-old man presents with fever, myalgia, non-productive cough, and headache 4 days after returning from Singapore. Rapid influenza diagnostic test is positive. Oseltamivir is started. Which step of the influenza virus life cycle does oseltamivir specifically inhibit?
- A Viral attachment by blocking haemagglutinin binding to sialic acid receptors
- B Release of progeny virions from infected cells by inhibiting neuraminidase-mediated cleavage of sialic acid ✓
- C Fusion of the viral envelope with the endosomal membrane mediated by haemagglutinin conformational change
- D Uncoating of the viral genome by blocking the M2 ion channel proton conductance
Correct answer: B. Release of progeny virions from infected cells by inhibiting neuraminidase-mediated cleavage of sialic acid
Explanation
Oseltamivir is a neuraminidase inhibitor that blocks the enzymatic activity of influenza neuraminidase, preventing cleavage of sialic acid residues and thus inhibiting release and spread of progeny virions. Option A describes no clinically used drug. Option C describes fusion, not targeted by current influenza drugs. Option D describes the mechanism of amantadine (M2 blocker), which is no longer recommended due to widespread resistance. Neuraminidase inhibitors are effective against both influenza A and C.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
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Written and medically reviewed by the StethoPrep medical team.