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Reducing the Risk Of Transmitting Herpes

June 10, 2008 - 7:30am
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Reducing the Risk Of Transmitting Herpes

Genital herpes is a common sexually transmitted disease (STD) in the US. It is caused by the herpes simplex viruses type 1 (HSV-1) and type 2 (HSV-2). Most genital herpes are caused by HSV-2. The Centers for Disease Control and Prevention (CDC) estimates that at least 45 million people age 12 and older have had a genital HSV infection—that is one out of every five adolescents or adults.

It is estimated that 1.6 million new cases of HSV-2 infection are acquired each year. HSV-2 is almost always transmitted during sexual contact with someone who has a genital HSV-2 infection. Most people know that herpes can be transmitted when symptoms—such as sores, blisters, cuts, pimples, bumps or a rash—are visible. But, a person with genital herpes can be contagious even without having symptoms.

Several antiviral medications are available to help reduce the frequency of outbreaks of herpes symptoms. Studies have found that daily antiviral therapy also reduces the amount of HSV that is shed on genital surfaces—the primary source of infection transmission. A study published in the January 1, 2004 issue of the New England Journal of Medicine examined whether taking valacyclovir (Valtrex), an antiviral drug, once daily could reduce the risk of sexual transmission of genital herpes.

About the study

The study included 1,484 couples in heterosexual, monogamous relationships. In each couple, one partner (the source partner) had clinically symptomatic genital herpes; the other partner (the susceptible partner) did not have genital herpes but was susceptible to contracting it. The source partners were randomly assigned to receive either 500 milligrams (mg) of valacyclovir or placebo once daily.

The partners were screened once a month for eight months. At each visit, safe sex practices, including the use of condoms, were discussed. The susceptible partners kept diaries concerning the couple’s sexual activity, condom use, and any symptoms that could be related to herpes. The diaries were reviewed at the monthly visit. In addition, serum samples were collected from susceptible partners and analyzed for signs of HSV.

The primary end point of the study was symptomatic new genital herpes in the susceptible partner.

The findings

At the end of eight months, 41 susceptible partners had contracted documented infections of HSV-2. Of the 41, 20 cases were associated with symptomatic new genital herpes. The remaining 21 cases were seroconversion only, meaning that the body had started to make antibodies against the infection, but was not yet displaying symptoms.

Of the 20 symptomatic cases:

  • 16 (2.2%) occurred among the partners of source partners taking placebo
  • 4 (0.5%) occurred among the partners of source partners taking valacyclovir
  • Of the 41 total cases of HSV:
  • 27 (3.6%) occurred among the partners of source partners taking placebo
  • 14 (1.9%) occurred among the partners of source partners taking valacyclovir

This translates into a significant (48%) reduction in risk for the couples taking valacyclovir once daily.

Interesting to note, some factors that increased the risk of transmission included:

  • Female sex of the susceptible partner
  • Greater number of sexual contacts
  • Shorter duration of genital herpes in the source partner

How does this affect you?

Contracting herpes will not kill you, but it cannot be cured and is highly contagious. A person with herpes may feel isolated and undesirable and worry if a successful monogamous relationship is possible with an STD. Studies have found that people with genital herpes and their sexual partners consider the transmission of HSV a major concern.

The results of this study can give hope to people with genital herpes—the risk of transmission was lower in people taking once-daily valacyclovir. However, the authors caution that although their study results show that antiviral medication can reduce the risk of HSV-2 transmission, it cannot eliminate it. It is still important to reveal the presence of genital herpes to a susceptible partner and to practice safe sex.


American Social Health Association

Centers for Disease Control and Prevention (CDC)


Corey L, et al. Once-daily valacyclovir to reduce the risk of transmission of genital herpes. New England Journal of Medicine. 2004;350(1):11-20.

Genital herpes: a hidden epidemic. US Food and Drug Administration Website. Available at: http://www.fda.gov/fdac/features/2002/202_herp.html . Accessed on: December 30, 2003.

Genital Herpes. Centers for Disease Control and Prevention Website. Available at: http://www.cdc.gov/std/Herpes/STDFact-Herpes.htm . Accessed on: December 30, 2003.

Herpes: get the facts. American Social Health Association Website. Available at: http://www.ashastd.org/hrc/educate.html . Accessed on December 30, 2003.

Last reviewed Jan 2, 2004 by Richard Glickman-Simon, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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