Anal warts are caused by the human papilloma virus, which is usually transmitted through sexual contact but not necessarily through anal intercourse. The same type of warts may occur on the penis, scrotum, vagina or labia. It is important to recognize and treat anal warts if you have them, as the risk of developing cancer is high.  The time from exposure to the virus and growth of the warts is commonly from one to six months, but it can be longer. During that time the virus remains in the tissues but is inactive. There are many types of human papilloma virus; some cause warts on the hands and feet and others cause genital and anal warts.