herpes simplex virus (HER-peez SIM-plex VY-rus)
A type of virus that causes herpes infections and has DNA as its genetic material. There are two types of herpes simplex viruses. Infections with type 1 viruses cause cold sores on the lips or nostrils. Infections with type 2 viruses cause sores on the genitals (external and internal sex organs and glands). Also called HHV, HSV, and human herpesvirus.