Abstract

Background Swingers, i.e. heterosexual couples who, as a couple, have sex with others within the swingers’ subculture, are a subpopulation at risk for Sexually Transmitted Infections(STI). Human papillomavirus (HPV) has proven to be highly prevalent in female swingers (unpublished data). The aim of this study is to assess how the different HPV genotypes are distributed within the sexual networks of swingers and whether certain HPV genotypes cluster.

Methods We build a sexual network of swingers based on the network data given by 115 swingers who participated in our prospective cohort network study on swingers between April 2011 and March 2012. The vaginal samples of all female swingers in the network and known in our STI clinic were tested for HPV. HPV genotypes were identified by the highly sensitive SPF 10 -LiPA 25 method detecting 25 different genital HPV genotypes. The multilevel transmission network consisted of the one-mode sexual network of the swingers and the two-mode network of swingers and the HPV genotypes. Distribution and clustering of HPV genotypes in the sexual network was assessed using multilevel network analysis.

Results The sexual network contained 1231 individual swingers of whom 556 female swingers. The sexual network consists of 38 separate components. Of 103 female swingers known in our STI clinic and tested for HPV, 96 (93%) were positive for at least one of the 25 HPV genotypes. All 25 HPV genotypes were present, but not equally distributed throughout the network. Some genotypes clustered together in specific components of the sexual network.

Conclusion All assessed genotypes of HPV were prevalent in the sexual networks of swingers. Despite the incomplete data in our study, multilevel network analysis turns out to be useful for studying transmission networks. Clustering of highly prevalent HPV could be used as a marker for sexual behaviour, potential STI risk and transmission in swingers.