Hormonal contraceptives increase risk of HSV-2 transmission

Women who are infected with herpes simplex virus type 2 (HSV-2) may have an increased risk of transmitting the virus to others if they use hormonal contraceptives or have certain bacterial vaginal infections, according to an article in the May 15 issue of Clinical Infectious Diseases, now available online.

The study underscores the importance of diagnosing and treating vaginal bacterial infections to prevent the spread of the herpes virus.

HSV-2 can remain latent in the body for some time, but when it becomes active and begins to multiply (a process known as "shedding"), it becomes transmissible to others, particularly through sexual activity. HSV-2 is a common infection--20 to 25 percent of American adults are infected--and can remain asymptomatic, so most people who are infected don't know it. Evidence suggests that HSV-2 infection can increase the risk of HIV transmission, which is further reason for trying to curb HSV-2's spread.

Researchers at the University of Pittsburgh and Magee-Womens Research Institute studied 330 women with HSV-2 infection to determine what factors heighten the risk of transmitting the virus to sexual partners. They found that the use of oral or injectable hormonal contraceptives is linked with genital tract shedding of HSV-2, which had been suggested by one prior study. However, they also found that two common types of bacterial infections, bacterial vaginosis (BV) and vaginal Group B streptococcus (GBS), were related to an increased risk of HSV-2 shedding, an association that had not previously been made. Vaginal yeast infections were not associated with increased shedding risk.

If confirmed in future studies, the findings would have significant implications, according to Thomas Cherpes, MD, of the Magee-Womens Research Institute and lead author of the study. "Because hormonal contraceptives are used by millions of people throughout the world, even a modest association with HSV-2 shedding would provide a significant contribution to the burgeoning genital herpes epidemic," he said. Dr. Cherpes added that further research is also required to determine if the type of contraceptive (such as oral birth control pills versus injectable Depo-Provera) affects shedding frequency.

The novel finding that some vaginal bacterial infections are also linked to a higher frequency of HSV-2 shedding could be important in controlling the spread of HSV-2. "BV is an infection that is readily treatable, and treatment for it is effective," Dr. Cherpes said. "I believe that treatment of BV will be shown to be an effective therapy to reduce the risk of HSV-2 shedding, but, again, further work is required."

Vaginal GBS becomes problematic when bacterial colonization is heavy; in pregnant women, GBS can result in infants with low birthweight or even severe infections. "In light of that, it's not that much of a leap to think that the alterations caused by the presence of GBS can also … result in increased [HSV-2] shedding frequency," Dr. Cherpes said. Penicillin and related drugs, though, are usually effective treatments for GBS.

Since there is no true cure for genital herpes, controlling its transmission is the only option. Women who have HSV-2 should consider alternate forms of contraception, such as condoms. And because there is no vaccine available for genital herpes, treating the bacterial infections that could predispose women to higher HSV-2 shedding frequency is probably one of the best ways to keep the virus in check, according to Dr. Cherpes. "I think it's going to be an important thing--it's not going to be a panacea, but it will help slow the spread [of HSV-2], and right now we want to do anything to slow the spread," he said.