The warts commonly seen on the skin are caused by a viral infection. The culprit is one of the HPVs (human papillomaviruses) that can be spread from person to person or be acquired through contact with a contaminated surface. Over 100 types of HPVs have been identified that infect skin or mucous membranes, depending on the virus type. HPV types that infect skin lead to the development of common skin warts. HPVs have gained widespread attention for their proven role in the development of genital and anal cancers, particularly cancer of the cervix. Specific "high risk" types of HPV that infect the mucosal tissue that lines the genital area are responsible for these carcinogenic (cancer-causing) effects. "High risk" HPVs have also been implicated in the development of a subset of head and neck cancers that develop in the area of the tonsils. There are also "low risk" HPV types that lead to the development of benign lesions in the genital area, such as genital warts. Some of these HPV types infect skin and cause warts in various locations on the body. Other HPV types cause benign growths, or papillomas, on the vocal cords.