Human herpes virus 6 (HHV6) is a recently observed agent found in the blood cells of a few patients with a variety of diseases. It causes roseola (a viral disease causing high fever and a skin rash in small children) and a variety of other illnesses associated with fever in that age group. This infection accounts for many of the cases of convulsions associated with fever in infancy (febrile seizures).
Herpes viruses typically infect the oral or genital mucosa. When herpes affects the mouth, it causes the typical "cold sores," which are painful sores or blisters that form on the lips, mouth, or gums. Prior to the development of the blisters, there may be a prodrome (early symptoms indicating onset of a particular disease) consisting of an itching, burning, or tingling sensation in the affected area. The virus remains dormant in the nervous system throughout life, and this is the reason that cold sores often recur in the same location.
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.