any of a subgroup of viruses belonging to the family Papovaviridae that infect birds and mammals, causing warts (wart) (papillomas) and other benign tumours in humans. They are small polygonal viruses containing circular double-stranded DNA; more than 55 distinct types of human papillomaviruses (HPVs) have been identified by DNA analysis. Skin warts are of two types, flat warts (which are superficial and usually on the hands) and plantar warts (on the soles of the feet and on the toes). Genital and venereal warts (condylomata acuminata) are caused by other types of papillomavirus.

Most papillomas, whether found on the skin or in the mucous membranes of the genital, anal, or oral cavities, are benign and may actually go unnoticed for years. A minority of genital and venereal warts, however, are visible, painful, or itchy. The papillomaviruses that cause these warts are transmitted by sexual intercourse, and it is estimated that about 10 percent of the adult population in developed countries has papilloma infections of the genital tract.

A number of papillomaviruses have been linked with various precancerous lesions and malignant tumours, especially cervical cancers. In fact, one or more of these high-risk type HPVs has been found in more than 90 percent of women diagnosed with cervical cancer. Their presence can be detected through an ordinary pap smear. In 2006 the first vaccine against HPV was approved. The vaccine is effective in preventing most cases of cervical cancer in women who have never been infected previously with the virus.