I understand your concern of witnessing something which might be a child abuse. In pediatric patients also, genital warts are caused by Human Papilloma Virus, just as they are in adults. It is one of the most common sexually transmitted infection. But in contrary to the popular belief, it can be transmitted to other by skin contact also. This virus resides in warts on the superficial layers of cells in body and can be spread to others by contact with those warts. If there is no confirmation of sexual contact, the child might have got the virus through direct contact with skin having genital warts. It is suspected to be abuse if there is a chance for sexual contact and the child is elder than 3 years. Moreover, there are ways to get the accused man tested to find whether he is infected with HPV, other than conventional methods of HPV testing. Hope I have made things clear. Best wishes.