HPV is short for human papilloma (pap-uh-LO-muh) virus. HPVs are a group of more than 100 related viruses. Each HPV virus in the group is given a number, which is called an HPV type. HPVs are called papilloma viruses because some of the HPV types cause warts or papillomas, which are non-cancerous tumors. The papilloma viruses are attracted to and are able to live only in squamous epithelial cells in the body. Squamous epithelial cells are thin, flat cells. They are found in the surface of the skin and in moist surfaces like the vagina, anus, cervix (the base of the womb at the top of the vagina), vulva (around the outside of the vagina), head of the penis, mouth, and throat. HPVs will not grow in other parts of the body.
Of the more than 100 known strains of HPV, about 60 HPV types cause warts on skin, such as that of the arms, chest, hands, and feet. These are the common warts.
The other 40 HPV types are mucosal types of HPV. "Mucosal" refers to the body's mucous membranes, or the moist surface layers that line organs and cavities of the body that open to the outside. For example, the vagina and anus have a moist top layer. The mucosal HPV types are also called the genital (or anogenital) type HPVs because they often affect the anal and genital area. The mucosal HPVs prefer the moist squamous cells found in this area. They do not grow in the skin.
Low-risk HPV types
Some types of genital HPV can cause cauliflower-shaped warts on or around the genitals and anus of both men and women. In women, warts may also appear on the cervix and vagina. This type of "genital wart" is called a condyloma acuminatum and is most often caused by HPV-6 or HPV-11. Because these genital warts very rarely grow into cancer, HPV-6 and HPV-11 are called "low-risk" viruses. These low-risk types can also cause low-grade changes in the cells of the cervix that do not develop into cancer.
High-risk HPV types
Other types of genital HPV have been linked with cancers in both men and women. These types are called "high-risk" because they can cause cancer. They also cause low-grade and high-grade changes in the cells of the cervix and pre-cancers. Doctors worry more about the high-grade changes and pre-cancers, because they are more likely to grow into cancers over time. Common high-risk HPV types include:
- HPV-16
- HPV-18
- HPV-31
- HPV-35
- HPV-39
- HPV-45
- HPV-51
- HPV-52
- HPV-58
Warts and cancer are caused by different types of HPV
In summary, low-risk HPV types can cause genital warts and low-grade changes in the cells. High-risk HPV types can cause low-grade changes, high-grade changes, pre-cancer, and cancer.
This diagram shows the different groups of HPV types and the problems each group can cause.
Feedback
