Sexual Intercourse (without condom) STD Activity Human Papillomavirus (HPV) October 10, 2016October 19, 2016 0 Comment HPV is the most common sexually transmitted infection. It lives in the body’s epithelial cells. These are flat and thin cells found on the skin’s surface and also on the surface of the vagina, anus, vulva, cervix, penis head, mouth, and throat.