A human papillomavirus (HPV) is a papillomavirus that infects the skin and mucous membranes of humans. Approximately 130 HPV types have been identified. Some HPV types cause warts (verrucae) or cancer, while others have no symptoms.

About 30-40 HPV types are typically transmitted through sexual contact and infect the anogenital region. Some sexually transmitted HPV types may cause genital warts, while others do not cause any noticeable signs of infection.

Persistent infection with "high-risk" HPV types — different from the ones that cause warts — may progress to precancerous lesions and invasive cancer. HPV infection is a cause of nearly all cases of cervical cancer.

A cervical Pap smear is used to detect cellular abnormalities. This allows targeted surgical removal of condylomatous and/or potentially precancerous lesions prior to the development of invasive cervical cancer. Although the widespread use of Pap testing has reduced the incidence and lethality of cervical cancer in developed countries, the disease still kills several hundred thousand women per year worldwide. HPV vaccines Gardasil and Cervarix, which prevent infection with some of the sexually transmitted HPV types that cause the most disease may lead to further decreases in the incidence of HPV-induced cancers.

United States

Estimates of prevalence vary from 14% to more than 90%. One reason for the difference is that some studies report women who currently have a detectable infection, while other studies report women who have ever had a detectable infection. Another cause of discrepancy is the difference in strains that were tested for.

HPV is the most common sexually transmitted infection in the United States. According to the National Cervical Cancer Coalition (NCCC), 11% of American women do not have regular cervical cancer screenings. Women who do not have regular cervical cancer screenings substantially increase their risk of developing cancer , because precancerous lesions will not be detected and removed. The American Cancer Society estimates that in 2008, about 11,070 women in the United States will be diagnosed with invasive cervical cancer, and about 3,870 US women will die from this disease. Most cases of HPV infection which become cancerous are due to a failure to get regular checkups and removal of precancerous lesions. Death from mere HPV infection is unlikely if a woman has regular checkups and participates in necessary follow-up procedures such as removal of lesions.

One study found that, during 2003–2004, at any given time, 26.8% of women aged 14 to 59 were infected with at least one type of HPV. This was higher than previous estimates. 15.2% were infected with one or more of the high-risk types that can cause cancer. However only 3.4% were infected with one or more of the four types prevented by the Gardasil vaccine, which was lower than previous estimates.