This also explains why gay men are a high-risk group: the mucous membrane is easily broken during anal sex, which is why the infection rate is so much higher than for vaginal intercourse.
這也解釋了男同性戀者之所以成為高危險群的原因：肛交容易導致黏膜破裂流血，愛滋入侵的機率自然大過異性性交。