The HSV viruses multiply in the human cell by overtaking and utilizing most of the human cells functions. One of the HSV steps in multiplication is to take control of the human cell's nucleus and alter its structure. The altered nucleus (enlarged and lobulated or multinucleated) is what actually is used to help diagnose herpes simplex infections by microscopic examination. The reason sores appear is because as they mature the many HSV particles rupture the human cell's membrane as they break out of the cell.
You should stop having sexual contact as soon as you feel warning signs of an outbreak. Warning signs may include a burning, itching, or tingling feeling on the genitals or around the mouth. Do not have vaginal, anal, or oral sex — even with a condom — until seven days after the warning signs stop or the sore heals. The virus can spread from sores not covered by the condom. It can also spread in sweat or vaginal fluids to places the condom doesn't cover.
A 2004 study in the New England Journal of Medicine found that suppressive therapy decreases the risk of HSV-2 transmission from symptomatic, infected partners to uninfected partners by 48%. So “the risk of transmission is significantly reduced, but cannot be eliminated even with suppressive therapy,” Johnston explains, and she stresses that the virus can be passed along even without signs or symptoms.