The herpes virus enters the body through the skin or mucous membranes, usually by way of sexual contact. The first time you experience an episode, called primary herpes, you will usually have painful sores and a flu-like syndrome as the virus spreads throughout the body. What's particularly unusual about the herpes virus is that it may enter some of the nerves of the body and travel toward the spine, remaining there in spite of antibodies that prevent infection elsewhere. Then, over the years, the virus travels down the nerves periodically to the skin, where it causes recurrent lesions. These blisters and sores, containing the contagious virus, last for 7 to 10 days and resolve spontaneously.
Some patients have only one outbreak, and others have recurrences for years.
The herpes virus may cause problems during pregnancy in two ways. If you had herpes before you got pregnant, you will very likely have built up antibodies by now, and the odds are small that the virus will cross the placenta and infect your fetus. But if you develop your first episode of herpes during pregnancy, the virus may indeed cross the placenta and infect the fetus. If this occurs during the first three months of pregnancy, the result can be miscarriage, birth defects, or fetal death. The more common scenario is that if the virus is present in the genital tract when the membranes are ruptured or when the fetus passes through the birth canal, the infection is passed to the fetus about half the time.