STUDY: Once-daily treatment cuts in half the risk of passing on the infection

JOURNAL: American Society for Microbiology

AUTHORS: Dr. Lawrence Corey

ABSTRACT: For the first time, a drug widely used to treat genital herpes has been shown to prevent its spread as well, offering a new way of curbing an infection already carried by one in five Americans.

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COMMENTARY: A study released Friday found that a once-daily Valtrex — known generically as valacyclovir cut in half the risk of passing on the infection when taken by people with herpes simplex virus type 2, the primary cause of genital herpes.

Until now, the only advice for avoiding herpes during sex has been to use condoms. While no one knows which is more effective, condoms are clearly not foolproof, since the virus spreads by contact with herpes sores, and condoms may not cover them all.

The latest research suggests a new use for Valtrex in so-called discordant couples — those in which one partner is infected and one is not. The drug is already widely prescribed to prevent and treat herpes flare-ups.

The Centers for Disease Control and Prevention estimates that 45 million American teenagers and adults are infected with the type 2 virus, which is almost always spread during sexual contact. The other herpes simplex virus, type 1, is much more common and causes cold sores. However, it too can cause genital infections if spread through oral-genital contact.

Usually, the type 2 virus causes only mild symptoms or no obvious sores at all. In fact, 90 percent of infected people do not realize they have it. Nevertheless, an unlucky minority suffers recurring painful genital sores.