n. (Med.) either of two forms of herpesvirus infection, distinguished as being caused by herpes simplex virus type 1 (HSV-1), which causes mostly sores and eruptions around the mouth (cold sores and fever blisters) and at other points above the waist, and herpes simplex virus type 2 (HSV-2), causing genital herpes. HSV-1 is also known in some cases to cause genital herpes infections. [ PJC ]