Hand-to-genital and genital-to-genital transmission of human papillomaviruses between male and female sexual partners (HITCH): a prospective cohort study.

BACKGROUND: Hand-to-genital contact is hypothesised to be a transmission mode of human papillomavirus (HPV) of the Alphapapillomavirus genus. We compared the relative importance of hand-to-genital and genital-to-genital HPV transmission between sexual partners.

METHODS: In this prospective cohort study, we recruited and followed up female university students aged 18-24 years and their male sexual partners in Montreal, QC, Canada (2005-11). Participants were eligible if they had initiated sexual activity within the past 6 months. Women were examined at clinic visits at baseline and every 4-6 months for up to 24 months. Men had a baseline visit and a single follow-up visit approximately 4 months later. Partners provided hand and genital swab samples, which we tested for DNA of 36 HPV types using PCR. We assessed predictors of incident type-specific HPV detections using Cox proportional hazards models.

FINDINGS: Participants were recruited between June 5, 2006, and April 4, 2013. 264 women and 291 men had valid hand samples. The hazard ratio (HR) of incident detection of HPV in genital samples from women was 5·0 (95% CI 1·5-16·4) when her partner was positive for the same HPV type on his hand versus negative, but adjustment for his genital HPV status reduced the HR to 0·5 (0·1-1·8). Similarly, the HR of incident detection of HPV on men's genitals was 17·4 (95% CI 7·9-38·5) when his partner was positive for the same HPV type on her hand versus negative, but adjustment for her genital HPV status reduced the HR to 2·3 (0·9-6·2). Conversely, the HR of type-specific incident detection of HPV in genital samples associated with partner genital HPV positivity was 19·3 (95% CI 11·8-31·8) for women and 28·4 (15·4-52·1) for men after adjustment for their hand HPV status.

INTERPRETATION: Clinicians can reassure their patients that HPV transmission is unlikely to occur through hand-to-genital contact. The majority of genital HPV infections are likely to be caused by genital-to-genital sexual transmission.

FUNDING: Canadian Institutes for Health Research, National Institutes of Health, Fonds de la Recherche en Santé du Québec, and Merck & Co.