Warts on a man's penis. Genital warts are caused by the human papilloma virus (HPV) and are spread through direct contact, including sexual activity. Once infected it can take weeks or months for warts to develop and in many cases warts will never develop. However, the individual will still be able to infect others. Some strains of HPV may lead to cancers of the affected areas. Treatment is either with chemicals that are applied directly to the warts or cryotherapy, which kills the warts by freezing them with liquid nitrogen.