Human papillomavirus (HPV) is the most common sexually transmitted infection (STI) that commonly causes skin or mucous membrane growths (warts). HPV is a virus with double-stranded circular DNA from the papillomavirus family. All HPVs have icosahedral capsids. HPV displays tropism toward the epithelial basal layer, which houses adult epithelial stem cells responsible for replenishing the epithelium with daughter cells. There are more than 100 varieties of human papillomavirus (HPV). Some types of HPV infection cause warts, and some (HPV 16 and 18) can cause different types of cancer, including cancers of the anus, penis, vagina, vulva and back of the throat (oropharyngeal). Worldwide, the risk of being infected at least once in a lifetime among both men and women is 50%. Vaccines can help protect against the strains of HPV most likely to cause genital warts or cervical cancer.