The human papillomavirus (HPV) is the main cause and risk factor of cervical cancer. HPV has been detected in virtually all invasive cervical cancers. About 1 in 4 U.S. females ages 14 - 59 are infected with HPV. The prevalence of HPV is highest (45%) in women ages 20 - 24.
How HPV Is Transmitted. HPV is spread primarily by having sex with a partner infected with HPV. HPV infection around the genitals is common, although most people have no symptoms. Some people with HPV infection will have visible genital warts. They are raised, flesh-colored soft growths that may occur singly or in clusters.
The HPV virus can cause warts on the penis, vulva, urethra, or around the anus. In women, HPV can invade the vagina and cervix. Vaginal and cervical warts are flat and not easily visible without special procedures. However, both men and women can be infected with the HPV virus and not have any visible warts on the genitalia. This is because this virus lives in the cells.
Most sexually active young women become infected with this virus, but only 10% remain infected for more than 5 years. In most cases, HPV goes away on its own. The risk for cervical cancer in infected women appears to be highest in those with persistent long-term infection with high-risk HPV strains. Generally, those infected for longer than 5 years have a higher risk (about 50% above normal).
How HPV Contributes to Cervical Cancer. Research suggests that most cervical cancers develop when certain genetic HPV strains activate certain oncogenes (cancer-causing genes). These oncogenes interfere with certain protective proteins, which normally limit cell growth. Once they are blocked, cell growth can accelerate, leading to tumor development and cancer.
HPV Genetic Types. There are more than 100 types of HPV. More than 30 genetic variants of human papillomaviruses can be passed through sexual contact from one person to another. People initially infected by one type of HPV are still at risk for infection from other types.
Low-risk HPV types, such as HPV 6 and 11, cause genital warts and cervical intraepithelial neoplasia I (CIN I). High-risk HPV types can cause cervical cancer. Less commonly, high-risk HPV types can cause as well as cancers of the vagina, vulva, anus, penis, oropharyngeal (throat, tongue, soft palate) and possibly lung cancers.
Of the high-risk types, HPV types 16 and 18 are known to be particularly dangerous. These two genetic types and six others (31, 33, 35, 45, 52, and 58) account for 95% of HPV-related cervical cancers. Other high-risk types are 39, 51, 56, 59, 68, 73, and 82. All are associated with cervical intraepithelial neoplasia II (CIN II) and cervical intraepithelial neoplasia III (CIN III). Types 26, 53, and 66 are also considered high risk.
The high-risk viruses generally produce flat and nearly invisible growths, compared to the usually harmless warts caused by low-risk HPV viruses.