Causes
Genital warts, including anal warts, are caused by human papillomavirus (HPV). HPV is a sexually transmitted infection (STI). In young people, HPV may go away on its own and might not cause any signs or symptoms. However, the virus can linger in the body and cause genital warts. Some types of HPV cause genital warts and others may lead to cancer, but the type of HPV that causes anal and genital warts does not generally lead to cancer.
HPV in general is spread from one person to another by direct contact with the mouth, anus, penis, or vagina of a person with HPV. Intercourse is not necessary to spread the infection. It can be transmitted by skin-to-skin contact. Transmission of HPV can occur even if warts are not visible.
According to the Centers for Disease Control and Prevention (CDC)Trusted Source, genital warts are most commonly spread through anal and vaginal sex. The CDC also states that nearly all men and women who are sexually active get HPV at some point in their lives.