HPV infection: How does it cause cervical cancer?

Human papillomavirus (HPV), a sexually transmitted infection, is the most common cause of cervical cancer. When a woman is exposed to HPV, her immune system usually prevents the virus from doing any harm. But in a small number of women, the virus survives for years and eventually converts some cells on the surface of the cervix into cancer cells. These changes happen very slowly. At first, the cells only show signs of a viral infection. Later, the cells become precancerous. Doctors refer to this as cervical intraepithelial neoplasia. In time, it progresses to invasive cervical cancer.

It's not clear why some women are more likely to develop cervical cancer. Cigarette smoking increases the risk of both precancerous changes and cancer of the cervix. The best way to prevent HPV infection is to have fewer sexual partners and use condoms.

In June 2006, the Food and Drug Administration (FDA) approved a vaccine that offers protection from the most dangerous types of HPV. The national Advisory Committee on Immunization Practices recommends routine vaccination for girls age 11 and 12, as well as girls and women ages 13 to 26 if they haven't received the vaccine already. The vaccine is most effective if given to girls before they become sexually active.