Herpes is a disease caused by herpes simplex [viruses].
An infection infects the epithelium cells of the skin or mucosa and dies. The virus then crawls into nearby nerve cells and persists there for life. A therapy cannot prevent this survival, it rather tries to prevent the virus from multiplying after an outbreak has occurred.
Two forms of herpes simplex viruses are known in humans:
https://de.wikipedia.org/wiki/Herpes_simplex (Wikipedia CC-by-sa-3.0)