The answer is, as beanie485 stated, that "during outbreaks" it is contagious.
The problem is in identifying the period when there is an "outbreak", especially the transition period between being non-contagious and contagious.
As mj29841 stated, the primary means of transmission is direct contact.
it is contagious avoid contact with the sores during outbreaks
The herpes simplex virus is contagious by direct contact, so avoid contact with known herpes sores (lesions).