Human papillomavirus (HPV) infection causes the vast majority of cervical cancers. HPV includes a group of about 100 viruses that cause warts in a variety of places on the body, including the cervix. Those that affect the genital tract are spread sexually.
Cervical strains of HPV are divided into "high risk" and "low risk" categories based on their association with cervical cancer. HPV 6 and HPV 11, for instance, cause most cases of genital warts but are considered “low risk” because they rarely lead to cancer. Other HPV strains, such as HPV 16, 18, 33, 35, and 45, are considered "high risk" because they have been linked with an increased risk for cervical and vaginal cancer.
Those women who start having sex at an early age, have multiple partners, or have a partner who has had multiple partners are at a greater risk for getting HPV, as are those with HIV infection (AIDS) and/or suppressed immune systems. Cigarette smoking may also raise risk because it suppresses the immune system and may damage the DNA in the cells of the cervix. Smokers are about twice as likely as nonsmokers to get cervical cancer.