Viral shedding occurs most often with herpes simplex virus infections. The virus remains in cells in the body after the first infection in a latent or dormant form. At some point this latency ends and the virus begins to multiply becoming transmittable. This shedding may or may not be accompanied by symptoms of a rash.
HSV-2 is more likely to shed than HSV-1, especially in women. As a matter of fact, it is possible that over half of the people infected with HSV-2 shed the virus at some time without having any symptoms or rash. It is also estimated that one-third of all HSV-2 infections are caused when a non-infected person comes in contact with someone who is shedding virus without symptoms.

