Human Papilloma Viruses (HPV) have been found in more than 20 different mammalian species. To date, there are more than 200 known HPV genotypes, identified numerically.
HPV infection in humans is very common and is the causal agent associated with cervical, anogenital (cervix, anus, penis) and oropharyngeal cancer. Over 40 HPV types infect the cervical, anogenital and oropharyngeal regions. Twenty-one have been classified as “high” risk for the development of malignant tumors. Others have been classified as “probable high risk” or “low risk” for the development of tumors. Recently, a vaccine has been developed to protect both men and women from the more aggressive HPV high risk viruses. The HPV risk classifications are as follows:
Human Papilloma Viruses that are known to cause cancer or are associated with the development of malignant tumors in the anogenital tracts or oropharynx.
High Risk types include: 16, 18, 26, 31, 33, 34, 35, 39, 45, 51, 52*, 53, 58, 56, 59, 66, 67, 68, 70, 73, 82
These viruses have genetic features very similar to High Risk Viruses and have occasionally been found in malignant tumors but the incidence of tumors is so low as to lack statistical confidence.
Possible High Risk types includes: 30, 64, 69
These viruses lack the genetic apparatus to cause malignant tumors in immunologically competent people, but can cause benign growths, usually on the skin.
Low Risk types include: 6, 11, 32, 40, 42, 43, 44, 54, 55, 61, 62, 71, 72, 74, 75, 77, 80, 81, 83, 84, 89
At this time, the exact risk classification of these viruses is not verified; however, there is a strong probability these will be categorized as low risk viruses. As more research is done, the World Health Organization does make updates to the risk ratings.
Unknown Risk types include: 41, 49, 60
Over 50% of sexually active men and women are infected by one or more HPV genotypes. HPV-16, considered to be one of the most aggressive viruses, is one of the most common types identified in sexually active individuals and is the most frequent cause of cancer in the anogenital (cervix, anus, penis) and oropharyngeal locations. So genotyping is an important procedure to verify the type of HPV virus “on board”.
In the U.S., the most frequent HPV viruses found in cancer include HPV-16, 18, 31, 52, and 58. The current vaccine, Gardasil 9, available for men and women between the ages of 9 and 26 generate antibody protection against the following HPV viruses: HPV-16, 18, 31, 33, 45, 52, 58 as well as against two low-risk wart causing viruses, HPV-6 and HPV-11.
The prevalence of HPV coincides with sexual activity. Although there appears to be a reduction in prevalence with increasing age, studies have shown an increase in incidence after age 55 that is attributed to reactivation of latent virus, an important feature of HPV.
Infection with the high risk HPV viruses, especially HPV-16, conveys a markedly increased risk of malignant transformation at all anogenital and oropharyngeal sites.
In families, it is important to realize that transmission of HPV viruses from parents to infants is quite common and may reflect the reservoir of positive HPV types in the younger population.
Vaccination with the latest HPV vaccine has been shown to be protective against the nine HPV viruses mentioned earlier, since the listed HPV viruses, especially HPV-16, are so aggressive. Unfortunately, the vaccine is only effective in the younger population (ages 9-26) who are capable of generating a robust immunologic response to the vaccine.
If, however, infection with a high risk virus is detected in the anogenital or oropharyngeal locations, the risk of malignancy increases, especially if the virus persists over time. Persistence of HPV-16 is of particular importance at any age and any location. HPV-16, as well as HPV-18, 31, 33, 45, 52, and 58 each is particularly aggressive and their persistence (the ability to detect the same virus over time) is a “red flag” requiring further evaluation. The location of a persistent high risk virus, whether cervical, anogenital, or oropharyngeal, requires examination by a health care professional experienced with significant changes in that anatomic location.