The herpes simplex virus, also known as HSV, is an infection that causes herpes. Herpes can appear in various parts of the body, most commonly on the genitals or mouth. There are two types of the herpes simplex virus.HSV-1, also known as oral herpes, can cause cold sores and fever blisters around the mouth and on the face.he herpes simplex virus is a contagious virus that can be passed from person to person through direct contact. Children will often contract HSV-1 from early contact with an infected adult. They then carry the virus with them for the rest of their life.