Women have roughly doubled odds of having herpes simplex virus type 2 (HSV-2) infection if they have abnormal vaginal flora or if they have ever had an uncircumcised sex partner, and their odds are increased by half if group B Streptococcus is present in the vagina.1 These "previously unidentified associations," found in a cross-sectional study among young, nonpregnant women in Pittsburgh, could point the way toward new interventions for reducing the incidence of genital herpes, according to the researchers, who describe the disease as "a significant public health concern." Other findings support independent associations between HSV-2 infection and recent smoking or douching (which have received little research attention), as well as more established risk factors.
To identify new and potentially modifiable factors associated with HSV-2 infection in women, researchers conducted a study among gynecologic patients at three Pittsburgh-area health clinics during 1998-2000. Women were eligible for the study if they were aged 18-30, were not pregnant, did not have vaginal bleeding and had not used vaginal products in the 24 hours before their examination. The women provided background information during interviews. Serum samples from the women were assayed for antibodies to herpes simplex virus type 1 (HSV-1) and HSV-2 (the more common cause of genital herpes). Vaginal swab and smear specimens were cultured for an assessment of the presence of various microorganisms; on the basis of these results, women were classified as having normal flora, intermediate flora or bacterial vaginosis. Tests for trichomoniasis and gonorrhea were done in some women.
The majority of the 1,207 women included in analyses were white (62%); about a third were black (34%), and the rest were of other ethnicities (4%). Laboratory test results indicated that 25% were infected with HSV-2; only 14% of these women were aware that they were infected.
At the univariate level, the prevalence of HSV-2 infection varied significantly according to a wide range of demographic and behavioral characteristics, women's history of reproductive tract infections and findings on their vaginal flora. Using these results, the researchers conducted logistic regression analysis to determine which factors were independently associated with HSV-2 prevalence.
In the multivariate analysis, black women's odds of being infected with HSV-2 were more than three times those of white women (odds ratio, 3.2). Compared with 18-20-year-olds, women aged 21-25 had a one-half increase in odds (1.5), while women aged 26-30 had nearly tripled odds (2.7).
The odds were elevated by half for women who reported smoking or douching in the past four months (odds ratio, 1.5 for each) and were similarly increased for women who reported having five or more male sex partners in their lifetime (1.4). Compared with women who had never had an uncircumcised sex partner, women who had ever had such a partner had more than doubled odds (2.2) and women who were unsure had nearly tripled odds (2.9).
Women's odds of having HSV-2 infection were about doubled if they had ever had bacterial vaginosis (1.8), gonorrhea (1.9) or trichomoniasis (2.3); the odds were elevated by half for women who had group B Streptococcus present in the vagina (1.5). In addition, compared with women who had normal vaginal flora, women who had intermediate flora or bacterial vaginosis had roughly doubled odds of infection (1.7 and 2.2, respectively). Similarly, among the women who were tested for trichomoniasis and gonorrhea, the odds of HSV-2 infection were twice as high for women who had altered vaginal flora and women who had bacterial vaginosis as for those with normal vaginal flora (2.2 and 1.9).
Some of the factors that this study links to HSV-2 infection are modifiable and could be targeted by prevention interventions, but as the researchers note, longitudinal studies will be needed to determine if they increase women's susceptibility to HSV-2 infection. Confirmation that bacterial vaginosis increases a woman's risk would have important implications because it is the most common vaginal infection, yet it can be effectively and inexpensively treated, the investigators contend. Noting that HSV-2 infection may also promote HIV infection, the researchers conclude that "in the absence of vaccines that effectively prevent the acquisition of HIV or HSV-2, treatment of [bacterial vaginosis] may represent a cost-effective means of slowing the transmission of these viruses."
1. Cherpes TL et al., Risk factors for infection with herpes simplex virus type 2: role of smoking, douching, uncircumcised males, and vaginal flora, Sexually Transmitted Diseases, 2003, 30(5):405-410.