The human papillomavirus (HPV) is considered the agent responsible for the most frequent forms of sexually transmitted infections in the general population. Its prevalence varies with age, and is higher in young women. There are over 120 strains of HPV, which differ in the types of tissue that they infect. More than 40 types can colonize the epithelium around the anus and genitals (cervix, vagina, vulva, rectum, urethra, penis, anus), and some of these are defined as high-risk HPV. Among the high-risk HPV strains, 16 and 18 are those most frequently implicated in cervical cancer. Other high-risk types are also associated with cervical cancer, but less frequently, while low-risk HPV types (those not linked to cancers) can still cause anogenital warts in both sexes. For several years a preventable vaccine has been available that is meant to be used prior to the start of sexual activity.
