Human Papilloma Viruses (HPVs)
Human papillomaviruses (HPVs) are a group of more than 120 different viruses. They are called papillomaviruses because certain types may cause warts, or papillomas, which are benign (non-cancerous) tumors. Some HPV types are spread by casual skin-to-skin contact with another person; for example, Type 1 causes plantar warts on the feet and types 2 and 3 cause warts on the fingers. (1) Others are acquired by intimate sexual contact.
Approximately 40 HPV types are primarily sexually transmitted from person to person (for example, genital-genital contact, oral-genital contact and sexual intercourse), infecting the oral, anal or genital areas of both men and women. (2) Genital HPV infections are very common: by 50 years of age, 70-80% of women will have acquired genital HPV infection.
The Centers for Disease Control and Prevention (CDC) estimates that 6.2 million Americans get a new genital HPV infection each year. (3) Sexually active adolescents and young adults are most likely to acquire genital HPV infection. Genital HPV infections are often acquired within a few months after beginning sexual activity. The prevalence declines with age after 25, but increases again in women about the time of menopause. (4) Genital infection with more than one type of HPV is common.
Some of these viruses can cause genital warts and others can cause anogenital cancers:
Outcomes of genital HPV infection
The vast majority of people recover from genital HPV infection uneventfully. Most genital HPV infections cause no symptoms and are cleared by the immune system within a few weeks or months. Because most persons with HPV infection do not show any symptoms,
However, some people develop persistent genital HPV infection.
High-risk HPVs can cause cancer. Although the vast majority of women recover uneventfully from high-risk genital HPV infection, some develop persistent infections with high-risk HPVs which can lead to cancer.
Detection of genital HPV infection
In developed countries, most women are diagnosed with HPV infection on the basis of abnormal Pap tests—the primary cancer-screening tool for cervical cancer. The Pap test screens for changes in cervical cells that are often caused by HPV and may indicate precancerous cells. Pap screening—and then the treatment of any abnormalities that are detected—prevents progression to cervical cancer.
It is estimated that 40 million women received Pap smears in the US in 1998 to screen for precancerous lesions and cancer. (12) Unfortunately—while widely available for free in the US—many women in the US (13) and most women in developing countries (11) do not have access to routine screening.
The most sensitive tests for the diagnosis of high-risk genital HPV infection involves the detection of viral DNA from cervical or vaginal samples. Many clinicians will perform HPV testing in women with mildly abnormal Pap tests, in order to guide further management. HPV testing along with Pap testing may also be recommended in women over 30 years of age.
HPV Infection in Men
Much less is known about the epidemiology and natural history of genital HPV infections in men than in women. (3, 15) The disease spectrum also ranges from unapparent infection to genital warts and anogenital cancers. Tests for genital HPVs in men have not been well standardized and as a consequence estimates of prevalence vary markedly. However, recent studies suggest that rates of infection in men may be similar to that in women.
HPV Infection in Children
Studies in young children have demonstrated that a small percentage of children 6-11 and 11-12 years of age already have been infected with HPV. (16,17) The proportion increases with age, peaking in adolescence and young adulthood.
Children can be infected with genital HPV by transmission from mother to newborn at delivery (which is rare), accidental inoculation (such as adult hand to genital contact during bathing) and by sexual abuse.
More Information about HPVs and Cancer
The American Cancer Society
Kahn JA, Hillard PA (2006) Progress in preventing cervical cancer and other HPV-related diseases, Part 1. Review in Contemporary Pediatrics.
2. National Cancer Institute (2005). Human Papillomaviruses and Cancer: Questions and Answers.
4. Trottier H, Franco EL. (2006). The epidemiology of genital human Papillomavirus infection. Vaccine, in press.
5. Burchell AN, Richardson H, Mahmud SM, et al. (2006) Modelling the sexual transmissibility of human Papillomavirus infection using stochastic computer simulation and empirical data from a cohort study of young women in Montreal, Canada. Amercian J Epidemiology 163:534-543.
6. Koutsky LA, Ault KA, Wheeler CM (2002). A Controlled Trial of a Human Papillomavirus Type 16 Vaccine. The New England Journal of Medicine, 347(21):1645-1651.
7. Castellsague X, Diaz M, de Sanjose S, et al. (2006). Worldwide human Papillomavirus etiology of cervical adenocarcinoma and its cofactors: implications for screening and prevention. J Natl Cancer Inst 98:303-315.
8. Scheurer ME, Tortolero-Luna G, Adler-Storthz K. ((2005) Human Papillomavirus infection: biology, epidemiology, and prevention. Int J Gynecol Cancer 15:727-46.
9. Saslow D, Runowicz CD, Solomon D, et al. (2002) American Cancer Society guideline for the early detection of cervical neoplasia and cancer. CA Cancer J Clin 52:342-62.
10. Ferlay J, Bray F, Pisani P. (2004) GLOBOCN 2002: cancer incidence, mortality and prevalence worldwide. IARC CancerBase No. 5. Version 2.0. Lyon: IARC Press.
11. Katz IT, Wright AA. (2006) Preventing cervical cancer in the developing world. N Engl J Med 354: 11.
12. Insinga RP, Glass AG, Rush BB. (2004) The health care costs of cervical human Papillomavirus-related disease. Am J Ob Gyn 191:114-20.
13. Adams Hillard PJ, Kahn JA. (2005) Understanding Papillomavirus in adolescence and young adulthood: opportunities for understanding and preventing infection. J Adol Health 37: S1-2.
14. Sawaya GF, Grimes DA. (1999) New technologies in cervical cytology screening: a word of caution. Obstet Gynecol 94:307-10.
15. Partridge JM, Koutsky LA. (2006) Genital human Papillomavirus infection in men. Lancet Infect Dis 6:21-31.
16. Stone KM, Karem KL, Sternberg MR, et al. (2002) Seroprevalence of human Papillomavirus type 16 infection in the United States. J IInfect Dis 186:1396-402.
17. Dunne EF, Karem KL, Sterberg MR, et al. (2005) Seroprevalence of human papillomavirus type 16 in children. J Infect Dis 191:1817-9.
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