What is human papillomavirus (HPV)?

Causes and Symptoms

Papillomaviruses are deoxyribonucleic acid (DNA) viruses than infect the skin and mucous membranes. Human papillomaviruses belong to a group of papillomaviruses that consists of nearly 120 strains. Most strains are virtually harmless, causing nothing more than benign skin warts (papillomas), while others cause genital warts
(condyloma acuminate) and may cause cancer.

Sexual contact is the primary mechanism by which the virus is acquired. About thirty HPV strains are sexually transmitted and can infect the external genitalia, urethra, anus, rectum, and sometimes the mouth and throat. Some low-risk strains cause genital warts, while the ten more virulent, high-risk strains cause abnormal Papanicolaou (Pap) tests and can in some instances cause cancer
of the cervix, vagina, vulva, penis, scrotum, anus, and/or the mouth and pharynx. Almost all cases of cervical cancer are the result of persistent HPV infection.

HPV is one of the most common sexually transmitted diseases. It has been estimated that more than 50 percent of sexually active people and up to 75 percent of sexually active women will develop an HPV infection during their lifetimes. Although the active viral infection is usually cleared by the immune system within a few months, it often remains dormant and can later cause a reinfection. Babies of infected women may contract potentially life-threatening HPV infections during delivery.

Women are more susceptible to developing genital warts. Many infected people, however, do not have genital warts. Infected women who are asymptomatic are often diagnosed by an abnormal Pap testing. In 2003, the Food and Drug Administration (FDA) approved the use of testing for high-risk HPV DNA as a routine screening procedure. DNA testing is also used as a confirmatory test for HPV after an abnormal Pap test.

Frequent Pap tests are the best way to diagnose HPV infections in asymptomatic women. About 10 percent of HPV-infected women will develop precancerous changes in their cervix, and about 8 percent of these women will develop the early stages of cervical cancer. Since persistent HPV infection is a hallmark of developing cervical cancer and since the cancer usually develops slowly over five to ten years, early diagnosis and treatment can be effective in preventing cervical cancer.

Genital warts are highly contagious and are transmitted through skin-to-skin contact from sexual activity. Risk reduction for HPV infection can be achieved by reducing the frequency of sexual contact. Condom use may partially reduce the risk of HPV infection in women. Since condoms do not cover all infected areas, however, their use does not eliminate the risk of infection. Research has suggested that microbicides may prevent infection if they are applied before sexual activity.

Treatment and Therapy

Since there is no cure for an HPV infection, the primary treatments are for warts.
Some treatments involve the use of topical ointments, creams, resins, and gels such as imiquimod (Aldara), podophyllin and podofilox (Condylox), and 5-fluorouracil, as well as trichloroacetic acid. Alternatively, warts may be removed by electrocautery, cryosurgery, laser, or conventional surgery.

In 2006, the FDA approved Gardasil, developed by Merck, and in 2009 approved Cervarix, developed by GlaxoSmith Kline, for use as preventive vaccines for the most prevalent HPV strains that cause cervical cancer and genital warts. Gardasil is active against two low-risk HPV strains that are the leading cause of genital warts and, as is Cervarix, active against two high-risk strains that cause up to 70 percent of cervical cancers in the United States. In 2010, the FDA approved the use of Gardasil for the treatment of precancerous lesions in an effort to prevent anal cancer. Gardasil is recommended for women between the ages of nine and twenty-six, and Cervarix is recommended for women between the ages of ten and twenty-five. The Center for Disease Control recommends that all eleven- and twelve-year-old girls receive the HPV vaccine, and that girls and women between thirteen and twenty-six receive "catch up" vaccinations. From 2008 to 2010, the percentage of girls between the ages of thirteen and seventeen who were behind on their vaccinations dropped from 84 to 75 percent. Routine Pap testing is still recommended, because the vaccines do not protect against all strains of HPV.

Perspective and Prospects

HPV was first described as a cause of skin warts in 1907. The relationship between sexual activity and cervical cancer was noted when it was discovered that women who have or who have had multiple sexual partners have a greater risk of developing cervical cancer than do women who have had few or no sexual partners. It was not until the 1980s that HPV was linked to cervical cancer.

The mechanism by which HPV causes cancer has recently been determined. Two proteins encoded by HPV DNA attach to and inactivate cellular proteins that control cell division. With these cellular proteins inactivated, the cell multiplies uncontrollably. Current research is directed toward the development of a vaccine that would inactivate the viral proteins that bind to and inhibit the proteins controlling cell division.

Since sisters of women with cervical cancer have a higher risk of developing cervical cancer, it is thought that genetics may be involved in the progression of the disease.

Bibliography

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Dizon Don S., and Michael L Krychman. Questions and Answers About Human Papilloma Virus (HPV). Sudbury, Mass.: Jones and Bartlett, 2011.

Eifel, Patricia J., and Charles Levenback, eds. Cancer of the Female Lower Genital Tract. Hamilton, Ont.: B. C. Becker, 2001.

Gross, Gerd, and Geo von Krogh, eds. Human Papillomavirus Infections in Dermatovenereology. Boca Raton, Fla.: CRC Press, 1997.

McCance, Dennis J., ed. Human Papilloma Viruses. New York: Elsevier Science, 2002.

Markowitz, Lauri E., et. al. “Quadrivalent Human Papillomavirus Vaccine: Recommendations of the Advisory Committee on Immunization Practices (ACIP).” Morbidity and Mortality Weekly Report (MMWR) 56 (March 23, 2007): 1–24.

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Wailoo, Keith. Three Shots at Prevention: The HPV Vaccine and the Politics of Medicine's Simple Solutions. Baltimore, Md.: Johns Hopkins University Press, 2010.