NAPLES, FLA. — Patients with genital herpes often believe they can't transmit the infection while they are asymptomatic, and the majority of transmissions are probably borne of this ignorance, Stephen K. Tyring, M.D., said at the annual meeting of the Florida Society of Dermatology and Dermatologic Surgery.
Many patients may be incredulous when you tell them this, because they have been told they must have a lesion or symptoms to transmit the virus.
With such patients, you can point out that 80% of the population is herpes simplex virus type-1 seropositive, but almost nobody ever kisses someone when they have a fever blister on their mouth, said Dr. Tyring, a dermatologist and infectious disease specialist who is medical director of the Center for Clinical Studies at the University of Texas Health Sciences Center, Houston.
The prevalence of herpes simplex type-2 (HSV-2) increased by 30% during the last 2 decades, Dr. Tyring noted. It is now estimated that 45 million people in the United States, or 15% of the population, are seropositive for HSV-2.
An estimated 80% of transmissions occur when the carrier is asymptomatic, Dr. Tyring said.
Women are at greater risk of acquiring the virus, he said. The overall rate of transmission from an infected partner to an uninfected partner is about 10% per year. But the annual rate rises if the infected partner is the male; the female partner has a 20% chance of becoming infected, and a 30% chance if she is seronegative for HSV-1. If the female is the infected partner, the male has a less than 10% chance of infection.
Condoms protect against transmission but are not foolproof, and they probably benefit women more than men. When men develop herpes lesions or have viral shedding, they tend to do so on the distal genitalia, which the condom covers. Women, however, shed virus into secretions that can get on the base of the penis or even the scrotum.
In a seminal study published last year, in which almost 1,500 infected individuals with seronegative partners were randomly assigned to 500 mg of valacyclovir or placebo once daily, Dr. Tyring and colleagues reported that the rate of transmission was reduced by 50% over an 8-month period (N. Engl. J. Med. 2004;350:11–20).
“The study used valacyclovir, but you can substitute famciclovir or acyclovir and probably get the same result,” Dr. Tyring said. “The bad news is, we don't have a cure. This is just one more tool in the armamentarium.”
The new genital herpes vaccine has been shown to be highly effective, but, unexpectedly, only in women. A major new trial is underway to better understand why this might be, and, specifically, the mucosal immunity women appear to develop.
Genital herpes increases the risk of HIV transmission two- to fivefold, Dr. Tyring said. This increased risk occurs because there is a reduced epithelial barrier in a person with herpes, but also because the individual with herpes has infiltrates of CD-4-positive cells where the lesions occur.
Studies have shown that one can use acyclovir, valacyclovir, or famciclovir to keep herpes in check in the HIV-infected individual—which not only addresses the herpes but sometimes improves the response to HIV therapy as well, Dr. Tyring said.
For HIV patients with resistant herpes, the Centers for Disease Control and Prevention recommends using a topical formulation of cidofovir.