Reducing the risk of transmitting genital herpes: advances in understanding and therapy.

BACKGROUND: This review considers the epidemiology and impact of genital herpes, discusses how herpes simplex virus-2 (HSV-2) is transmitted, and reviews data on methods of reducing the risk of HSV transmission. SCOPE: Information for the paper was identified through multiple PubMed searches. Information in the section on interventions was identified through PubMed searches using several pairs of key words (herpes and transmission, herpes and treatment, herpes and antiviral, herpes and valacyclovir, herpes and famciclovir, herpes and acyclovir, herpes and condom, herpes and clinical trial). The searches, conducted in January 2005, did not have date limits. Papers were selected for inclusion based on the author's judgment of their relevance to the topic of the review.
FINDINGS: An estimated 45 million persons in the United States have genital herpes infection, and new infections occur at a rate of approximately one million per year. Approximately 85% to 90% of infections are unrecognized and therefore undiagnosed. Individuals with genital HSV-2 infection shed virus during asymptomatic periods as well as symptomatic periods. In fact, transmission frequently occurs during periods of asymptomatic viral shedding. Asymptomatic viral shedding (1) occurs in the majority of patients with genital HSV-2 infection; (2) accounts for approximately one third of the days of viral shedding; (3) occurs regardless of duration of infection but is most frequent during the first year after infection; (4) occurs more than 7 days before or after a symptomatic recurrence 50% of the time; and (5) does not differ significantly when comparing patients with 1 to 12 annual recurrences to those with no recurrences. A recently published study of discordant couples counseled on safe sex practices found that once daily suppressive therapy with valacyclovir reduced the risk of transmission of HSV-2 in heterosexual immunocompetent adult couples discordant for HSV-2 infection. In an 8-month study, daily valacyclovir compared with placebo reduced the risk of acquisition of symptomatic genital HSV-2 infection by 75% (2.2% placebo vs. 0.5% valacyclovir; hazard ratio = 0.25; p = 0.008). The overall risk of acquisition of HSV-2 infection (defined via laboratory-confirmed symptoms or seroconversion) was reduced by 48% (3.6% placebo vs. 1.9% valacyclovir hazard ratio = 0.52; p = 0.04). The most common adverse events in the study were headache, nasopharyngitis, and upper respiratory infection.
CONCLUSION: Daily suppressive therapy is recommended as a therapeutic option for HSV-2 seropositive individuals at risk of transmitting HSV-2. Because no intervention completely protects against transmission of HSV, infected individuals and their partners should be counseled to use safer sex practices, including the use of condoms.