Genital herpes is a sexually transmitted viral infection affecting the skin of the genitals.

Herpes is caused by two viruses --

• Herpes simplex virus type 1 (HSV-1)
• Herpes simplex virus type 2 (HSV-2)

HSV-1, the virus responsible for common cold sores, can be transmitted through fluids from the mouth. It is responsible for only a small number of genital herpes cases. However, HSV can spread from the mouth to the genitals during oral sex.

HSV-2 causes most of the genital herpes cases. HSV-2 can be spread through secretions from the mouth or genitals.

Herpes simplex virus (HSV) is spread from one person to another by skin-to-skin contact. The virus is shed from visible sores, blisters, or a rash during outbreaks, but can also be shed from the affected area between outbreaks of symptoms.

HSV is transmitted to the area of skin with which it comes into contact. There are also some cases by which other types of contact can spread HSV. For example, a variant of herpes, known as herpes gladiatorum, can be passed on during body contact sports, such as wrestling.

Because the virus is transmitted through secretions from the mouth or genital tissue (mucosa), common sites of infection in men include:

• Anus
• Inner thighs
• Scrotum
• Shaft and head of the penis

Common sites of infection in women include:

• Anus
• Cervix
• Inner thighs
• Labia
• Vagina

The mouth can also be a site of infection in both sexes.

Research suggests that the virus can be transmitted even when there are no symptoms present, so that a sexual partner without obvious genital herpes sores can still transmit the illness. In fact, asymptomatic spread may actually contribute more to the spread of genital herpes than do active sores.

For people with no prior contact with HSV-1 or 2, initial infection involves both whole-body (systemic) and local symptoms.

Generalized symptoms include:

• Decreased appetite
• Fever
• Malaise
• Muscle aches

Local symptoms include repeated eruptions of small, painful blisters filled with clear, straw-colored fluid on the genitals, around the rectum, or covering nearby areas of skin. Before these blisters appear, the person may experience increased skin sensitivity, tingling, burning, itching, or pain at the site where the blisters will appear.

When the blisters break, they leave shallow ulcers that are very painful. These ulcers eventually crust over and slowly heal over a period of 7 - 14 days.

The outbreak may be accompanied by enlargement and tenderness of lymph nodes in the groin. Women also may develop vaginal discharge and painful urination. Men can develop painful urination if the lesion is near the opening of the urethra.

Once a person is infected, the virus hides within nerve cells, making it difficult for the immune system to find and destroy it. Within the nerve cells, the virus can remain dormant for a long period of time, which is called "latency."

The infection can reactivate at any time, at which point painful blisters again cover the genitals, anus, inner thigh, or mouth. A variety of events can trigger latent infection to become active, including:

• Fatigue.
• Mechanical irritation
• Menstruation
• Stress

Recurrent attacks can occur as seldom as once per year, or so often that the symptoms seem continuous. Recurrent infections in men are generally milder and shorter in duration than those in women.

• Viral culture of blister fluid from lesion is positive for herpes simplex virus. The herpes simplex virus can grow within 2 - 3 days.
• PCR from the blister fluid detects small amounts of DNA and can tell whether the herpes virus is present in the blister.
• Tzanck test of skin lesion may show results consistent with herpes virus infection. This test involves staining human cells within the blister fluid with a dye. If the cells from the fluid contain viral particles, they become visible. However, the test cannot determine which strain of virus is in the blister.

Recently developed antibody tests can determine whether a person has HSV-1 or HSV-2. These tests can also tell if a person has ever been exposed to either of these strains in the past (IgG test) or was just recently exposed to one of them (IgM test).