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

Background To investigate which sequential sexual acts involving different anatomical sites had the most affect on 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 2286 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 2468 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 2259 cases/million sex episodes. Conclusions Oropharynx-related sexual acts contribute to most gonorrhoea transmission. Condom use has a limited impact on gonorrhoea transmission.