Sexually transmitted infections (STIs) have remained a worldwide public health threat. It is difficult to control the spread of STIs, not only because of heterogeneous sexual transmission between men and women but also because of the complicated effects of sexual transmission among men who have sex with men (MSM) and mother-to-child transmission. Many studies point to the existence of a ‘bisexual bridge’, where STIs spread from the MSM network via bisexual connections. However, it is unclear how the MSM network affects heterosexual networks as well as mother-to-child transmission. To analyse the effect of MSM on the spread of STIs, we divided the population into four subpopulations: (i) women, (ii) men who have sex with women only (MSW), (iii) men who have sex with both men and women (MSMW), (iv) men who have sex with men exclusively (MSME). We calculated the type-reproduction numbers of these four subpopulations, and our analysis determined what preventive measures may be effective. Our analysis shows the impact of bisexual bridge on the spread of STIs does not outweigh their population size. Since MSM and mother-to-child transmission rates do not have a strong synergistic effect when combined, complementary prevention measures are needed. The methodologies and findings we have provided here will contribute greatly to the future development of public health.

中文翻译：

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男男性行为者 (MSM) 对性传播感染传播的影响

性传播感染 (STI) 仍然是全球公共卫生威胁。性传播感染难以控制，不仅是因为男女之间性传播的异质性，还因为男男性行为者（MSM）间性传播和母婴传播的复杂影响。许多研究指出存在“双性恋桥梁”，性传播感染通过双性恋连接从 MSM 网络传播。然而，目前尚不清楚 MSM 网络如何影响异性恋网络以及母婴传播。为了分析 MSM 对 STI 传播的影响，我们将人群分为四个亚群：(i) 女性，(ii) 只与女性发生性关系的男性 (MSW)，(iii) 与男性和女性发生性关系的男性女性 (MSMW)，(iv) 只与男性发生性关系的男性 (MSME)。我们计算了这四个亚群的类型繁殖数，我们的分析确定了哪些预防措施可能是有效的。我们的分析表明，双性恋桥梁对 STI 传播的影响并不超过其人口规模。由于 MSM 和母婴传播率在结合时不会产生很强的协同效应，因此需要采取互补的预防措施。我们在此提供的方法和发现将对公共卫生的未来发展做出巨大贡献。由于 MSM 和母婴传播率在结合时不会产生很强的协同效应，因此需要采取互补的预防措施。我们在此提供的方法和发现将对公共卫生的未来发展做出巨大贡献。由于 MSM 和母婴传播率在结合时不会产生很强的协同效应，因此需要采取互补的预防措施。我们在此提供的方法和发现将对公共卫生的未来发展做出巨大贡献。