In suspected viral encephalitis, which antiviral is used if HSV suspected?

• A. Acyclovir
• B. Ganciclovir
• C. Oseltamivir
• D. Ribavirin

Answer: (A)

When HSV is a concern in suspected encephalitis, start intravenous acyclovir right away. HSV encephalitis is the most dangerous and time-sensitive cause of sporadic encephalitis, and delaying treatment increases mortality and neurological damage. Acyclovir is a nucleoside analog that, after activation by viral thymidine kinase, inhibits viral DNA polymerase, making it highly effective against HSV (and also against VZV in many cases). Starting it early—even before confirmatory CSF PCR results—greatly improves outcomes, so the goal is empirical therapy as soon as HSV is a real possibility.

Ganciclovir is primarily used for CMV infections and has more bone marrow toxicity, so it’s not the first-line choice for HSV encephalitis. Oseltamivir targets influenza neuraminidase and has no role in treating HSV encephalitis. Ribavirin has activity against a range of viruses in specific contexts but is not standard therapy for HSV encephalitis and carries notable toxicity; it’s not the preferred option here.

In short, the best choice for suspected HSV encephalitis is acyclovir, started promptly to reduce mortality and long-term impairment, with diagnostic tests pursued concurrently to confirm the causative virus.