Updated: February 1, 2007
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:
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.
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 US13 and most women in developing countries11 do not have access to routine screening.
Costs for all HPV-related expenditures from one health plan, extrapolated to the entire US were $3.4 billion of which $2.1 billion was for screening tests.12
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.
These tests have greatly reduced the mortality from cervical cancer by allowing treatment before the cancer develops or in early stages of the cancer. Unfortunately, 50% of newly diagnosed invasive cervical cancers are detected in women who have not been previously screened with Pap smears and another 10% have not had a Pap test in more than 5 years.14
Much less is known about the epidemiology and natural history of genital HPV infections in men than in women.315 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.
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.1617 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.