The herpes simplex viruses HSV-1 and HSV-2 are linear, double-stranded DNA viruses that share ~50% sequence homology. Exposure to HSV at mucosal surfaces or abraded skin sites permits viral entry and replication in cells of the epidermis and dermis prior to infection of neuronal cells and development of a latent infection in ganglia.

• Reactivation occurs when normal viral gene expression resumes, with reappearance of the virus on mucosal surfaces.
• Both antibody-mediated and cell-mediated immunity (including type-specific immunity) are clinically important.