'Certainly not in the heterosexual public eye': a qualitative study of the sociodemographic, behavioural and attitudinal drivers of syphilis among heterosexual-identifying people in England (the NEXUS study)

BackgroundRecent increases in syphilis diagnoses among heterosexual individuals are a growing public health concern. We aimed to qualitatively assess the risk factors, lifestyles, and contexts facilitating syphilis transmission among heterosexually-identifying individuals in England through the NEXUS study. Methods and FindingsNEXUS was a qualitative study based on semi-structured one-to-one interviews conducted between December 2023 and September 2024. Heterosexually-identifying individuals diagnosed with primary, secondary, or early latent syphilis in the previous year at a sexual health service in one of three regions in England were recruited. Interviews were also conducted with healthcare professionals involved in syphilis management. An analytical framework approach identified salient themes from interview transcripts. The service-user data were triangulated using healthcare professional data. Interviews were conducted with 19 service-users and seven healthcare professionals. Syphilis acquisition was primarily associated with condomless vaginal or oral sex. Half (10/19) reported multiple partners around the time of diagnosis; other known risk factors, like swinging (multiple concurrent partners) (1/19), sex work (3/19), or transmission among heterosexually-identifying men who have sex with men (1/19), were linked to a minority of infections. Of those reporting a single partner (9/19), four were in a believed exclusive relationship. Many had low perceptions of STI risk but intended to alter sexual behaviours post-diagnosis. Syphilis knowledge was limited among heterosexual individuals and initially seeking medical advice for symptoms from non-sexual health specialists sometimes led to diagnosis delays. Service-users suggested information on syphilis epidemiology, symptoms, and prevention, conveyed through National Health Service sources and mass media, would have been beneficial. ConclusionsWe identified a range of contexts associated with syphilis transmission. While multiple partners were common, infections also occurred through infrequent or novel practices or among those with few sexual encounters. Increasing awareness of syphilis among heterosexually-identifying individuals and healthcare professionals working in specialties other than sexual health is important to improve detection, facilitate treatment, and reduce transmission.