Herpes Simplex: Herpes is a viral infection caused by herpes simplex 1 or 2. Herpes simplex type 1 is usually found on the mouth in the form of a cold sore or fever blister. Herpes simplex type 2 is usually responsible for outbreaks in the genital region. It is possible, however, to have type 1 in the genital area and type 2 on the mouth. Herpes is one of the most common sexually transmitted diseases. The herpes virus generally infects the mucosal tissue of the vagina, penis, or anus through a process called viral shedding.