The herpes simplex virus (HSV), which causes genital herpes, comes in two forms: type 1 and type 2. HSV type 2 is the most common cause of genital herpes. HSV type 1 causes cold sores or fever blisters on the lips, but it can be spread to the genital area and cause genital herpes, as well. Researchers have identified 6 other herpes viruses that commonly infect humans. These are varicella zoster, which causes chickenpox; cytomegalovirus; Epstein-Barr, and herpes viruses 6, 7, and 8. Herpes virus 8 is also known as Kaposi sarcoma herpes virus, or KSHV.

HSV sores can appear on parts of the body where the virus has entered through a cut or scrape on the skin.

It also can be passed on during oral sex. HSV can be passed on at any time. It doesn't matter whether a lesion is present or not. Therefore, someone in a relationship with an HSV-infected person should take precautions to avoid transmission every time sexual intercourse or oral sex occurs.

Most people infected with the virus, however, never have any symptoms, so they aren't aware that they have herpes. If symptoms appear with the first attack, they show up within 2 to 12 days after contracting the virus and continue for 2 to 3 weeks. Within a few days of the initial symptoms, sores appear in the genital area. Other symptoms include fever, headache, muscle aches, painful or difficult urination, and swollen glands. Later outbreaks of the virus may involve milder symptoms that stay in the area where the lesion appears and typically don't last as long.

With genital infection, the nerves at the lower part of the spine are most commonly infected. The virus hides out in nerve cells until the next outbreak. When the virus becomes active again, it travels along the nerves to the skin, where it causes sores to appear near the site of the original infection.

Sometimes outbreaks can occur several times a year; for other people, the outbreaks can be once or twice in a lifetime. Sometimes the outbreak causes no symptoms, but the virus is still active and the person is infectious. Scientists don't know what causes the virus to become active. Stress and sunlight may both play a role. In any case, a person with HSV should assume he or she is always infectious.

If a woman gets HSV while pregnant, she can pass the virus on to her unborn child. Although this type of HSV infection is rare, it can cause serious consequences. These can include severe developmental abnormalities and even death of the baby in utero. If a woman has an outbreak during pregnancy, but it's not her first outbreak, the chances of passing on the virus are low. The main risk of HSV in pregnancy is passing the virus to the baby during labor and delivery. The baby can develop an infection of the skin, eyes, and mouth, or the baby's entire central nervous system can be infected. Less commonly, a baby can develop an infection that involves several internal organs, as well as the central nervous system. A woman who has an outbreak during labor, with either symptoms or sores around or in the vagina, should have a cesarean delivery to protect the newborn from contracting the virus.

If a lesion is present, the doctor can take a swab of it, as well as the mucus membranes. The doctor may also do a blood test for antibodies. Some older blood tests still being used can't always tell if the virus is HSV1 or HSV2.

The symptoms are treated with medication. Currently, there is no cure for HSV. Antiviral medication can help prevent or shorten future outbreaks.

A person with HSV should avoid sexual contact from the time the symptoms are first felt until all sores have healed and symptoms have cleared up. Between outbreaks, the person should use a condom to help prevent spreading the virus. But a person with HSV should realize that transmission of the virus is still possible even with a condom.