Infections with the virus that causes genital herpes are common among teen girls, a new study shows.

While none of the young women in the study had oral or genital herpes symptoms, some of those who tested positive for the virus were shedding it in their vaginal area, meaning it would be possible for them to transmit the infection to others, Dr. Kenneth H. Fife of the Indiana University School of Medicine in Indianapolis and colleagues report.

“It was something that we sort of expected to find based on the incidence of other sexually transmitted infections in this population,” Fife told Reuters Health in an interview.

A national survey of the US population conducted between 1988 and 1994 found that more than one in five people over 12 had blood tests that showed evidence for infection with herpes simplex virus 2 (HSV 2), the virus typically responsible for genital herpes, Fife and his team note in their report in the July issue of Sexually Transmitted Diseases. This represents a 30 percent increase from 1976-1980. There is also evidence that genital infections with HSV 1, which normally causes cold sores around the mouth, are on the rise, they add.

To examine the incidence and prevalence of both strains of the virus among adolescent women, Fife and his team analyzed data from a study in which a group of young women were followed closely to determine if they contracted any sexually transmitted infections. Their analysis included results of blood and genital specimen tests obtained every three months from100 women aged 14 to 18.

At the study’s outset, they found, 59.6 percent of the women tested positive for HSV 1, while 13.5 percent carried HSV 2. During the follow-up period, from 1999 to 2004, four of the study participants contracted new HSV 1 infections, while seven acquired HSV 2.

Among the women who developed new HSV 2 infections, none had symptoms of genital herpes, but three were shedding the virus in their vaginal area.

It is likely that at least some of the new HSV 1 infections that occurred among women in the study were genital, given that genital HSV 1 infections are quite common in young adults, the researchers note.

They conclude, “HSV infections are common in adolescent women.” They point out that efforts to reduce these infections “need to target children before adolescence.”

SOURCE: Sexually Transmitted Diseases, July 2006.