HPV is one of the most common sexually transmitted infections in the United States. HPV includes a group of more than 200 related viruses that cause warts in a variety of places on the body, including the cervix. More than 40 types of HPV affect the genital tract and are easily spread through direct sexual contact of skin and mucous membranes. Nearly all cervical cancers are caused by HPV, but not all HPV strains cause cervical cancer. Some types of HPV cause non-genital warts and are not sexually transmitted.
Cervical strains of HPV are divided into "high risk" and "low risk" categories based on their association with cervical cancer. Persistent infections with high risk types of human papillomavirus (HPV) cause almost all cervical cancers. About a dozen HPV strains, such as HPV 16, 18, 33, 35, and 39, are considered "high risk" because they are linked to an increased risk for cervical and vaginal cancer. Two HPV types, 16 and 18, cause 70% of all cervical cancers. HPV 6 and HPV 11, on the other hand, cause 90% of all genital warts but are considered "low risk" because they rarely lead to cancer.
Women who are sexually active at an early age and have multiple partners, or have a partner who has had multiple partners, or has had partners with cervical cancer are at a greater risk for getting HPV. Individuals with HIV infection (AIDS) and/or suppressed immune systems are also at increased risk. 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.