SAN DIEGO, CALIFORNIA--A large, international study has shown that when people who have genital herpes take a daily dose of a drug used to treat the disease, they dramatically reduce the odds that they will transmit the infection to their sexual partners. The findings--the first time a drug has been shown to cut sexual transmission of a virus--may also help slow the spread of HIV.
According to the U.S. Centers for Disease Control and Prevention in Atlanta, herpes simplex virus type-2 (HSV-2) infects about 1 million people each year in the United States alone. The chronic infection causes periodic blisters and rashes. Often, HSV-2 does not produce detectable symptoms, even when a person is “shedding” high levels of the virus. Condoms offer only about 50% protection from the HSV-2, as it is frequently spread through skin-to-skin contact, says Larry Corey, an infectious-disease specialist at the University of Washington and the Fred Hutchinson Cancer Research Center in Seattle.
The 4-year study, presented by Corey here at the 42nd Interscience Conference on Antimicrobial Agents and Chemotherapy, followed 1484 monogamous, heterosexual couples at 126 sites around the world. Each couple had one partner infected with HSV-2. The researchers randomly divided the infected participants into two groups: one received a placebo, and the other received a daily dose valacyclovir, a drug taken regularly by about 10% of those with HSV-2 to combat its symptoms. In all, treatment cut the transmission of HSV-2 by 50%. (Couples were also counseled to use condoms, although 56% reported that they never did.) GlaxoSmithKline, the maker of valacyclovir, sponsored the trial.
“It's a very important study,” said epidemiologist H. Hunter Handsfield, who heads the sexually transmitted disease program for Seattle's Public Health Department and was not one of the study's co-authors. “Although there's a common-sense notion that giving therapy for communicable diseases will help others, it has rarely been documented.” The finding may also lead to a new strategy to thwart the spread of HIV. Several studies have shown that HSV-2 infection makes people much more susceptible to infection with HIV, because sores on their skin ease the virus's passage into the bloodstream; that suggests that reducing the spread of HSV-2, and the sores it produces, might affect HIV transmission rates.