Herpes simplex virus (HSV) is a relatively large enveloped virus with a 152-kb linear double-stranded genome that codes for about 90 RNA transcripts, 84 of which appear to encode proteins.

Herpes simplex virus 1 and 2 (HSV-1 and HSV-2) are two members of the human Herpesviridae family, a set of viruses that produce viral infections in the majority of humans.Both HSV-1 (which produces most cold sores) and HSV-2 (which produces most genital herpes) are common and contagious. They can be spread when an infected person begins shedding the virus.