The role of sequential sexual acts on Neisseria gonorrhoea transmissions between anatomical sites in men who have sex with men: a mathematical modelling study

Objectives: To investigate which sequential sexual acts involving different anatomical sites had the most affect the transmission of gonorrhoea in men who have sex with men (MSM). Methods: A mathematical model was constructed to simulate gonorrhoea transmission between the sequential sexual acts involving the oropharynx, urethra, and anorectum. We simulated 1,000,000 sexual episodes using data of the sexual behaviours of a recent cohort of MSM and identified which acts contributed most to transmission events. The potential impact of condom use on gonorrhoea transmissions was also evaluated. Results: We used data on 2,286 sex episodes that involved 294 different sexual patterns from 312 MSM followed for 12 weeks. Of the 1,000,000 model-simulated sexual episodes, 83.50% of 2,468 transmissions occurred in sexual episodes that involved the oropharynx, with kissing accounting for the majority (68.85%). The three most frequent individual sexual behavioural patterns were ‘kissing only’, ‘kissing-receptive oral sex-insertive anal sex’, and ‘kissing-insertive oral sex-receptive anal sex’. These contributed to 341, 209, and 166 transmissions, respectively. The increasing coverage of condoms (80%) could potentially reduce gonorrhoea transmissions by 8.49% to 2,259 cases/million sex episodes. Conclusions: Oropharynx-related sexual acts contribute to most gonorrhoea transmission. Condom use has a limited impact on gonorrhoea transmission. Keywords: Neisseria gonorrhoea; sequential sexual behaviour; oropharynx-related transmission; anatomical site-specific transmission; men who have sex with men; mathematical model; interventions; sexually transmitted disease.  What is already known on this topic - Gonorrhoea is the second most common sexually transmitted disease in the world. Understanding the transmission of Neisseria gonorrhoea is essential in controlling the further spread of gonorrhoea.  What this study adds - We develop a new mathematical model to simulate the transmission of gonorrhoea through sequential sexual acts, specifically focusing on the role of oropharynx-related acts in the spread of Neisseria gonorrhoea.  How this study might affect research, practice or policy – The study suggests that oropharynx-related sexual acts contribute to most gonorrhoea transmission, and interventions aimed at the oropharynx are necessary.