What are human papillomaviruses?
Human papillomaviruses (HPVs) are a group of more than 200 related viruses. More than 40 HPV types can be easily spread through direct sexual contact, from the skin and mucous membranes of infected people to the skin and mucous membranes of their partners. They can be spread by vaginal, anal, and oral sex.1 Other HPV types are responsible for non-genital warts, which are not sexually transmitted.
Sexually transmitted HPV types fall into two categories:
- Low-risk HPVs, which do not cause cancer but can cause skin warts (technically known as condylomata acuminata) on or around the genitals and anus. For example, HPV types 6 and 11 cause 90% of all genital warts. HPV types 6 and 11 also cause recurrent respiratory papillomatosis, a less common disease in which benign tumors grow in the air passages leading from the nose and mouth into the lungs.
- High-risk HPVs, which can cause cancer. About a dozen high-risk HPV types have been identified. Two of these, HPV types 16 and 18, are responsible for most HPV-caused cancers.2,3
HPV infections are the most common sexually transmitted infections in the United States. About 14 million new genital HPV infections occur each year.4 In fact, the Centers for Disease Control and Prevention (CDC) estimates that more than 90% and 80%, respectively, of sexually active men and women will be infected with at least one type of HPV at some point in their lives.5 Around one-half of these infections are with a high-risk HPV type.6
Most high-risk HPV infections occur without any symptoms, go away within 1 to 2 years, and do not cause cancer. Some HPV infections, however, can persist for many years. Persistent infections with high-risk HPV types can lead to cell changes that, if untreated, may progress to cancer.
Which cancers are caused by HPV?
High-risk HPVs cause several types of cancer.
- Cervical cancer: Virtually all cases of cervical cancer are caused by HPV, and just two HPV types, 16 and 18, are responsible for about 70% of all cases.7,8
- Anal cancer: About 95% of anal cancers are caused by HPV. Most of these are caused by HPV type 16.
- Oropharyngeal cancers (cancers of the middle part of the throat, including the soft palate, the base of the tongue, and the tonsils): About 70% of oropharyngeal cancers are caused by HPV. In the United States, more than half of cancers diagnosed in the oropharynx are linked to HPV type 16.9
- Rarer cancers: HPV causes about 65% of vaginal cancers, 50% of vulvar cancers, and 35% of penile cancers.10 Most of these are caused by HPV type 16.
High-risk HPV types cause approximately 5% of all cancers worldwide.11 In the United States, high-risk HPV types cause approximately 3% of all cancer cases among women and 2% of all cancer cases among men.12