The virus that causes genital herpes can be spread when it is active in the body. Some people have symptoms, such as herpes blisters, when the virus is active. These blisters are usually on the genitals but can be in the mouth and other areas of the body as well, such as the thighs, buttocks, and anal area. Other people may have no symptoms, but the active virus may still be present on the skin and other body areas (such as the rectal area and fluids from the penis and vagina), and can be passed on to others.

Regular skin - skin on the hand, for example - is protected against all but the most massive invasion because of a natural barrier on the skin called keratin. Keratin is waxy and strong. Just as it repels water, it repels herpes virus particles. Unless the keratin is torn, in a cut for instance, the virus cannot get to an epithelial cell (the type of cells that make up the skin). In mucous membranes, however, like those lining the mouth, eye, and genital area, the barrier is very thin, and the epithelial cells are very near the skin surface. This is where access is easiest.

To transfer the infection:

  • one person needs to have an active infection with herpes
  • there must be friction for heat and for removal of infected cells from the surface of the infected person
  • there must be moisture for easy travel of the virus and to prevent drying
  • there must be contact with exposed epithelial cells of another susceptible person

It's important to keep in mind that people can have an active, contagious herpes infection without any symptoms or visible sores. This is called viral shedding, and it causes up to 70% of new infections with genital herpes.

Thus, genital herpes tends to be sexually transmitted. Other types of transmission are possible but not usual. Most friction-, moisture-, and heat-producing contact between 2 people involving the skin of the genitals is sexual. Herpes simplex can be transmitted, for example, from a penile sore to a vagina. However, transmission of genital herpes does not actually require genital penetration, and it can be transmitted even when there are no visible sores. Sexual contact may include a nongenital sore contacting a genital target. In other words, herpes may be transmitted from the source partner's mouth to the other partner's vagina, or from mouth to penis, penis to mouth, finger to penis, penis to anus, or any other combination. The only requirements are infected cells and exposure to new cells belonging to a new, susceptible person, along with heat and moisture.

These requirements are also met in a variety of contact sports. Herpes simplex virus does not care if sex is happening. Sure, herpes likes sex, but sex is only one type of contact sport that generates heat, moisture, and friction-based skin-to-skin contact. Herpes can be spread during wrestling, rugby, or any other contact sport that exposes a new susceptible host to infectious virus, and thus provides the new environmental opportunities the virus constantly seeks to restart its reproductive cycle in a new host.

Stephen Sacks, MD, FRCPC, with revisions by the MediResource clinical team