Warts are caused by one of 100 virsuses in the human papillomavirus (HPV) family. Some types of HPV cause warts on the skin, while other types of HPV viruses cause warts on the genitals and rectal area. Warts on the skin and genital warts are, therefore, caused by different strains of the same virus and are removed in different ways. These types of HPV (hand warts) do not cause genital warts.