Herpes simplex viruses (HSV) belong to the subfamily of Alphaherpesvirinae. Herpes viruses consists of a relatively large linear DNA genome of double-stranded DNA 150 kb in length, encased within an icosahedral protein cage called the capsid, which is wrapped in a lipid bilayer called the envelope. The envelope is joined to the capsid by means of a tegument. This complete particle is known as the virion. The genome of Herpes viruses encodes some 100-200 genes. These genes encode a variety of proteins involved in forming the capsid, tegument and envelope of the virus, as well as controlling the replication and infectivity of the virus.