Morphology: Enveloped, double-stranded DNA virus. Family Herpesviridae, subfamily Alphaherpesvirinae. Establishes latency in sacral ganglia after primary genital infection; periodic reactivation.
Typical drugs
- #1Valacyclovir— Preferred PO — q12h dosing. 500 mg BID episodic, 500 mg–1 g daily chronic suppression.
- #2Acyclovir— IV for severe / disseminated / neonatal disease. PO 400 mg TID is less convenient.
- #3Famciclovir— Alternative PO — 1 g BID × 1 day for episodic recurrence.
Empiric therapy when resistant
ACV/VACV/FCV failure in immunocompromised → foscarnet 40–60 mg/kg q8h IV (renally dosed).
Resistance mechanisms
altered-target
Thymidine kinase mutations → ACV resistance
Example: Mostly immunocompromised on chronic suppression. Salvage: foscarnet.
Resistance notes
Acyclovir resistance ~1% immunocompetent; 5–10% in HSCT chronic suppressive use.
Pearls
Most genital herpes is HSV-2 but increasingly HSV-1 acquired via orogenital contact. Initial episode severe; recurrences shorter. Chronic suppression (valacyclovir 500 mg daily) reduces both symptomatic recurrences AND transmission to seronegative partners (~50% reduction). Disclosure + condoms + suppression is the harm-reduction triad. Neonatal HSV-2 is the disaster — peri-partum transmission from undiagnosed maternal infection; C-section if active lesions; IV ACV 20 mg/kg q8h × 21 days for neonatal disseminated / CNS / mucocutaneous disease. Type-specific serology to distinguish HSV-1 vs HSV-2 partner counseling.