Human papillomaviruses (HPV) are DNA viruses that are sexually transmitted and replicated in cells. There are over 120 types of HPV, which differ in the types of tissue they infect. More than 40 types affect the anal and genital epithelium (cervix, vagina, vulva, rectum, urethra, anus, penis) and some of these are defined HPV high-risk are those related to the emergence of various types of tumors, especially of the cervix, but also the penis, anus, vulva, and others.
Of high-risk HPV, HPV 16 and the 18 are those most frequently implicated in cervical cancer, being responsible respectively for about 60% and 10% of all cervical cancers. Other high-risk types are associated with cervical cancer, but less frequently, while low risk HPV (those not linked to cancers) can still cause anogenital warts in both sexes.
Most HPV infections are transient, because the virus is eliminated by the immune system before developing a pathogenic effect. In case of persistent infection, the time between infection and the occurrence of precancerous lesions is about five years, while the latency for the onset of cervical cancer can be 20-30 years.
Mode of transmission
HPV infection is transmitted mainly through vaginal or anal intercourse with partners carrying the virus. The risk of contracting the virus and then increases with the number of sexual partners. Other types of sex (oral or manual) can be transmission routes, but much more rarely.
Prevention, treatment and vaccine
Until recently, the only way to prevent Cervical cancer through screening was done using a Pap test is still recommended every three years for women between 25 and 64 years. The smear test makes it possible to identify precancerous lesions and to intervene before it evolve into carcinoma. Recently the European Medicines Agency ( EMEA ) approved in Europe, the first HPV vaccine (Gardasil ®). Gardasil ® prevents injuries caused by four types of the virus: HPV 16 and 18 (total associated with about 70% of all cervical cancers), 6 and 11 (responsible for 90% of genital warts).
The vaccination series consists of the administration, intramuscular injection of three doses, in the second and third at a distance of 2 and 6 months after the first. The clinical efficacy of the vaccine was evaluated in women between 16 and 26 years. Among those who were not infected with HPV types in the vaccine, the efficacy of three doses in preventing precancerous lesions associated with these types was 95%. The vaccine, however, has no therapeutic effect, and the effectiveness drops to 46% if the women infected with at least one of HPV types in the vaccine and those who had not completed the vaccination series.
The availability of the vaccine thus opens the way for a possible strategy for prevention of cervical cancer, screening alongside policies. In August 2006 the WHO published a guide for the introduction of HPV vaccines, that the pre-adolescents between 9 and 13 years of age are the primary target: the vaccination before the start of sexual relations is in fact particularly advantageous because it leads to a high security before a possible infection with HPV.