Herpes simplex virus (HSV) type 1, a ubiquitous pathogen latently infecting human sensory ganglion cells is associated with mucocutaneous disorders which are common and sometimes associated with serious outcomes in the eye and central nervous system. Molecular epidemiological analyses of HSV-1 are pertinent to (i) determination of the transmission of a particular HSV-1 strain (e.g., in case of a nosocomial infection), (ii) identification of co-infecting HSV-1 strains and resultant recombinant viruses (e.g., between former occupant wildtype HSV-1 and attenuated HSV-1 injected for gene therapy), (iii) elucidation of the association of genomic characteristics of HSV-1 strains with clinical manifestations, providing clues to the pathogenesis of infection in humans, and (iv) the use of HSV-1 genotype as a marker of human populations. (C) 1998 Lippincott Williams & Wilkins.