Steve Gale, Facebook asked:
How does HSV1 virus, the Herpes simplex virus that causes cold sores, hide between times when itís active?
It hides inside nerve cells. It exists as a small piece of DNA, which is just the genetic material for the virus, hiding inside the nerve cellís nucleus alongside the DNA in that cell. As a result, itís out of reach of the immune system and because itís not making any proteins that the cell can display on its surface, the immune system doesnít tend to touch it. It can then use the genetic recipe book in that DNA to come back to life later, producing new virus particles that go back down the nerve cell, come out on the skin, and produce an infectious lesion that is unsightly, but is also highly infectious and you can pass it on.