A human papillomavirus (HPV), a member of the papillomavirus family, is capable of infecting humans. HPVs establish productive infections in the skin or mucous membranes. Most of the 200 known types cause no symptoms in most people. Some types can cause warts, while others can lead to cancer.
There are more than 30 to 40 types of HPV that are typically transmitted through sexual contact and infect the anogenital region. High risk HPV, can lead to cancer, in fact HPV infection is a cause of nearly all cases of cervical cancer. Most HPVs in young females are temporary and have little long-term significance. 70% are gone in a year while 90% disappear after two years. In those that the infection persists there is a high risk of cancer. This progression to cancer can be prevented through standard strategies.
Pap smears have helped to reduce the fatalities of cervical cancer although there were still 3,900 deaths in the U.S. in 2008. Worldwide there are an estimated 270,000 deaths due to cervical cancer. There are two vaccines that help prevent the type of HPV that cause cervical cancer that should lead to further decreases in infection.
HPV is estimated to be the most common sexually transmitted infection in the United States. Most sexually active people will acquire genital HPV infection sometime in their life. HPV prevalence estimates vary from 14% to 90%. The variance comes from some studies reporting those currently infected while others report those who have been previously infected. Prevalence decreases with age which may be due to HPV being cleared by the immune system. Infection is slow taking 12-24 hours. Once a HPV viron invades a cell the virus can be transmitted. It also may take months to years before lesions appear. The time from infection to clinical detection makes it difficult to detect which partner may have been the source of infection.
There around a dozen “high-risk” types of HPV. In the US, HPV is expected to replace tobacco as the main causative agent for oral cancer. Genital warts are contagious although the common, flat, and plantar warts are less likely to spread. Most people who contract warts clear the infection rapidly without ever actually developing any warts. Condoms do offer some protection but are not 100% effective. There are 40 identified HPV types that infect the genital tract. Warts are the only visible sign of low-risk genital HPV.