Human papillomavirus (HPV) is not one virus, but a family of them. (There are more than 100 types.) HPV can be sexually transmitted, and it can cause genital warts and cervical cancer. HPV infections are very common—half of sexually active people in the U.S. get HPV—but relatively few people have lasting health effects. HPV usually goes away on its own without treatment, although vaccines can protect against the virus.