Westover Heights Clinic - Transmission

    Genital herpes is transmitted from one person to another through sexual contact. Sexual contact includes intercourse, oral-genital contact, and rubbing the genitals together without being separated by clothing.  This is sometimes known as "outercourse."

    When someone has a cold sore on their mouth (or simply has an oral infection with no sores present) and gives oral sex to someone else, the virus can be spread from the mouth of the infected partner to the genitals of the uninfected person.  The receiver of the oral sex might then get genital herpes. The virus type doesn't change (that is, it doesn't change from type 1 to type 2), but the cold sore virus will simply live, and possibly recur, in the area of the genitals. Cold sores have been around for a long, long time, and some people find it hard to accept that these can indeed be the source of genital herpes infections. But as oral sex becomes more common, the incidence of getting genital herpes in this way is increasing. Anal intercourse can also transmit the virus to the rectal area, though many people who get herpes outbreaks around the rectum and the buttocks have never had anal sex.  This can occur when the virus travels along a slightly different nerve pathway to get to the surface of the skin than along the nerve pathway that goes to the genitals.

    Adults and children can (but rarely do) transmit the virus from one part of their own body to another. This phenomenon is called autoinoculation. Autoinoculation almost always occurs during the first outbreak when the immune system has not yet produced an immune response to the herpes. Autoinoculation is quite uncommon or many more children would have genital herpes because of touching their cold sores and then touching their genitals as children often do.  One specific area of concern is the transmission of the virus from the mouth to the eyes. If someone has a cold sore, it is important that they wash their hands carefully between touching a sore and rubbing their eyes. Saliva should not be used to wet contact lenses. HSV 1, not HSV 2, causes the majority of ocular HSV.

    One of the most difficult things to learn about herpes is that there is a chance that the virus can be transmitted when there are no apparent lesions.  Women can have virus on their cervix with no sores on the outside of their body. Men can have the virus present inside of the urethra with no external sores. The virus can be given off from the genital skin of both men and women with no sores through microscopic breaks in the skin.  This is called asymptomatic shedding; giving off the virus from the body when there are no visible symptoms.  The more sensitive our virus detection methods become, the more viral shedding we can identify. Shedding rates vary based on location of virus and type of virus.  The chart below is a guideline about how often shedding happens in healthy adults.

HSV 2 genital     15-20% of days evaluated
HSV 1 genital        3-5% of days evaluated
HSV 1 oral             18% of days evaluated
HSV 2 oral               1% of days evaluated

    We know that up to 70% of new cases of herpes are transmitted from someone showing no apparent symptoms at the time they infect their partner. Research has shown that asymptomatic shedding occurs more frequently during the first year of having herpes than it does subsequently.

    This information about viral shedding may present difficult emotional concerns about sexuality, and, unfortunately, there are no guarantees for fail-safe methods of dealing with this thorny issue. It is probably true that many people who have herpes DO have symptomatic episodes when they give off virus but do not recognize them as herpes symptoms.  We thought for a long time that all herpes was "remarkable" meaning that we would know for sure if an outbreak were occurring.  But now we know this isn't the case and that herpes has multiple faces; many of them unrecognizable.  The truth is that most genital herpes symptoms are mild and very easy to miss.

    People don't get genital herpes from an inanimate object such as a hot tub or swimming pool. Generally, the chemicals present in hot tubs and swimming pools easily kill the virus. We do recommend, however, that during an outbreak, one not share their towel with another person. Towels stay wet and warm for a while, and the virus could conceivably live for a very short time in that environment. Warm water and soap will easily kill the vulnerable virus on surfaces and clothing. Some studies have shown that the virus can live for a short time outside of the body, but there are no documented cases of anyone contracting herpes from an inanimate object.

    People often want to know what the chances are of getting herpes from another person. Overall, the risk is about 10% per year that an infected male would transmit HSV 2 to an uninfected female.  That is, if 100 infected men were having one-on-one sex with 100 uninfected women, about 10 women would get infected per year. If the situation were reversed, about 4 uninfected men would get herpes in a year from infected women. We do not have good studies on same gender couple transmission rates as the sexual practices in same gender couples vary a good deal which makes accurate transmission rates more difficult to obtain.

 
    The studies that gave us those numbers were based on the following criteria:

1) No sex during outbreaks,
2) No daily antiviral medication and,
3) No regular use of condoms.

    A study completed in the summer of 2002 evaluated whether antiviral therapy, taken daily, could reduce the risk of transmission of HSV 2 from an infected partner to an uninfected one in healthy, heterosexual adults over the age of 18.  The person with herpes took either Valtrex 500 mg daily or a placebo (a sugar pill or inactive substance).  The study followed the couples for a total of 8 months, drawing the blood of the uninfected partner monthly to look for infection.  The study found that the taking of Valtrex daily reduced transmission by 48% over placebo.

    We know that condoms also reduce the risk of transmission by about half.  Condoms appear to offer a bit better protection for uninfected women than they do for uninfected men.

    When both condoms and antiviral therapy are used, transmission rates can be greatly reduced. Even then, there is a small chance that transmission can occur.