HSV is a linear, double-strand DNA virus, with two subtypes (HSV-1 and HSV-2).

• Exposure to HSV at mucosal surfaces or abraded skin sites permits viral entry into cells of the epidermis and dermis, viral replication, entry into neuronal cells, and centrifugal spread throughout the body.
• More than 90% of adults have antibodies to HSV-1 by age 40; 15-20% of the U.S. population has antibodies to HSV-2, with a higher prevalence in low-income countries.
• Unrecognized carriage of HSV-2 and frequent asymptomatic reactivations of virus from the genital tract foster the continued spread of HSV disease.
• Genital lesions caused by HSV-1 have lower recurrence rates in the first year (~55%) than those caused by HSV-2 (~90%).