Genital Herpes: Can Transmission Be Prevented?

Abstinence is the only guaranteed method to prevent the transmission of genital herpes. Many people with genital herpes report that they avoid sex during outbreaks because the genital ulcers that signal an outbreak can be painful, taking the pleasure out of sexual relations. Other couples refrain from sexual relations because they don't want to transmit the herpes to their partners.

"There is logic in that thinking, since there is more virus present on the genitalia during an outbreak than between outbreaks. Yet, if avoidance of sexual relations during outbreaks of genital herpes was really a reliable method to prevent transmission, they why do so many people have genital herpes?" This question was posed today at the American Academy of Dermatology's 56th Annual Meeting in Orlando, by Stephen K. Tyring, MD, PhD, Professor of Dermatology, University of Texas Medical Branch, Galveston.

Herpes simplex virus (HSV) can be present on the genitalia even in the absence of any signs or symptoms of an outbreak, even the most ëcareful'

couples can and do transmit the virus. This phenomenon is called asymptomatic viral shedding, and is well documented as the source of at least 80% of the cases of genital herpes transmission.

Another method widely used to prevent genital herpes is the condom. "Indeed, condoms do reduce the risk of transmission of genital herpes and other sexually transmitted disease, and their use is widely recommended. However, it is also widely recognized that condoms can slip and/or break. In addition, condoms can only protect the skin that they cover. Many cases of herpes and other sexually transmitted diseases can be transmitted to/from skin not covered by the condom," Dr. Tyring said.

The majority of persons seropositive for HSV-2 have never had a recognized clinical outbreak of genital herpes. Yet, these people may also occasionally shed the virus and transmit the disease. Despite the use of condoms and the avoidance of sex, the chance of transmitting genital herpes to an uninfected partner has been estimated at 10% per year. The risk of a man transmitting to his female partner is far greater than the reverse. In fact, the females' chances of acquiring genital herpes are estimated at 30% each year.

If so many people have genital herpes and suffer little or no symptoms, why is it important to seek improvements in the prevention of genital herpes? "First, the person who acquires genital herpes may suffer more severe and more frequent outbreaks than did the persons from whom they acquired HSV-2. For example, the man with genital herpes may only experience mild, or even rare outbreaks. If he passes it to his wife, she may suffer painful genital ulcers for one to two weeks preceding each menstrual cycle. "The worst scenario could occur if she were to acquire HSV-2 during pregnancy due to the high rate of morbidity and mortality associated with neonatal herpes. Another reason to reduce the transmission of HSV-2 is that genital ulcers facilitate the transmission of HIV, the cause of AIDS," Dr. Tyring said.

Two new methods to reduce transmission of genital herpes are being evaluated: vaccinate the susceptible person; or use antiviral drugs to reduce outbreaks and asymptomatic viral shedding in person with genital herpes.

The first method is currently under investigation. Today vaccines exist for prevention of 14 viral diseases. Vaccines to prevent genital herpes are not made from the herpes virus, but are simply copies of proteins on the surface of the virus. Therefore it is impossible to become infected from the vaccine. "In fact, over 10,000 people have received the vaccine and no serious side effects have resulted. What remains unknown, is whether the vaccine actually protects a person from being infected with the herpes virus," Dr. Tyring said.

Persons having received the vaccine will have their blood tested periodically over the next two years to determine if the level of antibodies to HSV-2 remains high. Most importantly, these patients will help the physicians determine whether their rate of acquiring genital herpes is significantly less than those who did not receive the vaccine.

A recent study has begun to answer the question of whether a genital herpes patient taking a daily dose of an antiviral drug can lower the risk of transmitting HSV-2 to an uninfected partner. Three antiviral drugs are approved to treat or suppress outbreaks of genital herpes: acyclovir, famciclovir and valacyclovir. Most clinically apparent outbreaks can be prevented by taking one of these drugs daily. In addition, daily acyclovir reduces asymptomatic viral shedding by 95%.

The same is assumed to be true of the other two drugs, one of which, valacyclovir, is actually a more potent form of acyclovir. Since valacyclovir taken once daily prevents clinical outbreaks in most herpes patients and is believed to have a profound effect on reducing asymptomatic viral shedding, it should help prevent transmission to the uninfected person. Other promising interventions are being evaluated.

The American Academy of Dermatology is the world's largest organization of physicians with over 10,000 members worldwide.