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.
A scary finding is that more cases of genital herpes than ever before are now being caused by HSV-1 (the type most people assume only causes mouth sores), and about 85 percent of people with genital herpes don’t even know it. (7) Studies show that about 50 percent of the new genital herpes infections in young adults are due to HSV-1 and about 40 percent in older adults. The fact that most people don’t ever find out they’re infected is one of the reasons that transmission rates are steadily climbing.
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.