Which of the following antivirals may be used to treat influenza A and B:

Rationale: A. Oseltamivir is a neuraminidase inhibitor that prevents the release of new viral particles from infected host cells. It is clinically effective against both influenza A and B strains when administered within 48 hours of symptom onset. This medication is the standard of care for reducing the duration and severity of the flu in both outpatient and hospitalized populations. B. Acyclovir is a DNA polymerase inhibitor specifically designed to treat herpesvirus infections, such as herpes simplex (HSV) and varicella-zoster (VZV). It possesses no pharmacological activity against the influenza virus, which is an RNA virus with a different replication mechanism. Using this agent for the flu would be clinically inappropriate and would not provide any therapeutic benefit to the patient. C. Ketoconazole is a broad-spectrum antifungal agent used to treat systemic and superficial mycoses by inhibiting fungal ergosterol synthesis. It has no antiviral properties and is not used to treat respiratory viruses like the influenza virus. Furthermore, ketoconazole is typically administered orally or topically; an "inhaled" version is not a standard clinical formulation for treating upper respiratory tract infections. D. This option is incorrect because only oseltamivir has the appropriate antiviral profile to target the neuraminidase enzyme of the influenza virus. Acyclovir and ketoconazole target entirely different classes of pathogens (herpesviruses and fungi, respectively). Proper antimicrobial stewardship requires the selection of an agent that specifically targets the identified or suspected pathogen to ensure efficacy and prevent resistance.