HSV-1 and another herpes virus -- herpes simplex virus type 2 (HSV-2) -- make up genital herpes. An estimated 45 million people aged 12 or older in the U.S. have had genital herpes, says the CDC. That's one in five teens or adults. The number of people in the U.S. with genital herpes increased 30% from the late 1970s to the early 1990s, says the CDC.
HSV-1 has been traditionally thought to spread "above the waist," while HSV-2 has a reputation for transmission through sexual behavior "below the belt," say University of Pittsburgh researchers.
But now, they've shown that women can also catch HSV-1 through vaginal or oral sex.
More Risk With Oral Sex, Vaginal Intercourse
Their new study showed that women who received oral sex were nearly nine times as likely to become infected with HSV-1 as those who were sexually abstinent. That was true, even if the sexually active women only had oral sex without vaginal intercourse.
Women who had vaginal intercourse were more than six times more likely as sexually abstinent women to get HSV-1, says the study.
Those results were found by monitoring herpes infection in 1,200 young women in the Pittsburgh area. After an initial clinical visit, the women returned for three follow-up appointments, scheduled four months apart. They disclosed their sexual practices and gave blood samples, which were screened for herpes viruses.
All of the women were 18 to 30 years old. At the study's start, 38% had HSV-1. That's a low rate, says the study, which appears in the February edition of the journal Sexually Transmitted Diseases.
The study didn't cover whether the women's partners had herpes, and it couldn't rule out kissing as the means of transmission.
Herpes Risk Rising for Young Adults
The rate of childhood HSV-1 infection has been falling in the U.S. and other developed countries. That's left a "burgeoning population of young adults who are susceptible to either oral or genital HSV-1 infection," says the study.
"Because oral HSV-1 infections are less frequent in childhood and adolescence, future prevention strategies will be needed to consider increased susceptibility for HSV-1 among young adults, and the important contribution of HSV-1 to the growing genital herpes epidemic," says researcher Thomas Cherpes, MD, in a news release. Cherpes works in the infectious diseases division of the University of Pittsburgh's medical school.
HSV-2 infection doesn't help protect against HSV-1 write the researchers, calling for a herpes vaccine that targets both types of the virus.