HERPES SIMPLEX VIRUS
Two distinct epidemiologic and antigenic types of HSV exist (HSV-1 and HSV-2). The DNA genomes of both are linear, double-stranded molecules containing approximately 160 kbp. Their nucleic acids demonstrate approximately 50% base sequence homology, which is considerably greater than that shown between these viruses and other her-pesviruses. HSV-1 and HSV-2 share antigens in almost all their surface glycoproteins and other structural polypeptides, but differences in glycoprotein gB enable them to be distin-guished (ie, HSV-1 has gB1 and HSV-2 has gB2). Numerous strains of both HSV-1 and HSV-2 exist. In fact, by restriction endonuclease analysis of the viral genome, most strains of either HSV-1 or HSV-2 are found to differ somewhat, except in epidemiologi-cally related cases such as motherâ€“infant and sexual partners.