The epidemiology of sexually transmitted infections (STIs) is inherently linked to host mating dynamics. Studies across many taxa show that adult sex ratio, a major determinant of host mating dynamics, is often skewed - sometimes strongly - toward males or females. However, few predictions exist for the effects of skewed sex ratio on STI epidemiology, and none when coupled with sex biased disease characteristics. Here we use mathematical modelling to examine how interactions between sex ratio and disease characteristics affect STI prevalence in males and females. Notably, we find that while overall disease prevalence peaks at equal sex ratios, prevalence per sex peaks at skewed sex ratios. Furthermore, disease characteristics, sex-biased or not, drive predictable differences in male and female STI prevalence as sex ratio varies, with higher transmission and lower virulence generally increasing differences between the sexes for a given sex ratio. Our work reveals new insights into how STI prevalence in males and females depends on a complex interaction between host population sex ratio and disease characteristics.

性传播感染（STI）的流行病学与宿主交配动态有着内在的联系。对许多分类群的研究表明，成虫性别比例是宿主交配动态的主要决定因素，通常偏向雄性或雌性，有时甚至强烈偏向。然而，对于性别比例失衡对性传播感染流行病学的影响几乎没有预测，而且当与性别偏向的疾病特征相结合时，也没有预测。在这里，我们使用数学模型来研究性别比例和疾病特征之间的相互作用如何影响男性和女性性传播感染的患病率。值得注意的是，我们发现，虽然总体疾病患病率在性别比例相等时达到峰值，但每种性别的患病率在性别比例倾斜时达到峰值。此外，随着性别比例的变化，疾病特征，无论是否存在性别偏见，都会导致男性和女性性传播感染患病率存在​​可预测的差异，较高的传播力和较低的毒力通常会增加给定性别比例下性别之间的差异。我们的工作揭示了关于男性和女性性传播感染患病率如何取决于宿主人口性别比和疾病特征之间复杂相互作用的新见解。