HPV infections affect the skin and/or lining of cells inside the body. In most people, the infection causes no harm, and disappears naturally overtime. However, HPV strains such as HPV16 and 18 are known to be a major cause of cervical cancer in women. A high percentage of penile and anal cancers have also been linked to HPV16. In certain high-risk groups, such as men who have sex with men (MSM) as well as HIV-positive individuals, an even higher prevalence of anal infections are related to HPV.