Human papillomavirus (HPV) infection is a cause of nearly all cases of cervical cancer.[21] Most women will successfully clear HPV infections within 18 months. Those that have a prolonged infection with a high-risk type[22] (e.g. types 16, 18, 31, 45) are more likely to develop Cervical Intraepithelial Neoplasia, due to the effects that HPV has on DNA.