A recent prospective longitudinal cohort study [24] found a significant association between UAI and HCV infection, but did not include potential confounders that could explain other sexual or non-sexual routes of HCV infection, such as frequency of anal intercourse, group sex, sex-associated bleeding, traumatising sexual practices such as fisting, use of PDE-inhibitors, lesion-prone STIs (i.e. sexual), or (procto-)surgical interventions [25], tattooing or NIDU (i.e. non-sexual). Here, ALDH7A1 is linked to sexually transmitted disease.