Human papillomavirus: often harmless but in some cases carcinogenic.

(1) Globally, papillomavirus infections are very widespread in the general population worldwide. More than 100 genotypes of human papillomavirus (HPV) have been identified; they differ in targeted tissue and carcinogenic activity. (2) This article describes the clinical manifestations, prevalence and modes of transmission of human papillomavirus infections, and the role of HPV in human cancer. A systematic literature review was carried out to answer these questions based on methods developed by Prescrire. (3) The most frequent clinical manifestations of human papillomavirus infection are cutaneous and anogenital growths such as warts, papillomata and condylomata. The HPV genotypes linked to skin infections differ from those infecting the anogenital area. Genotypes HPV-16 and HPV-18 are frequently associated with high-grade cervical dysplasia. (4) The frequency of HPV infections varies widely from one population to another. HPV (usually genotype 16) is found in 1.5% to 44% of cervical smears. In the 1990s, 25% of women between 20 and 29 years of age in the United States were seropositive for HPV-16. (5) Papillomavirus is highly persistent in the environment, on contaminated objects, linen, floors. Skin infections can occur through indirect or direct contact. Most anogenital infections are sexually transmitted. (6) Most papillomavirus infections are asymptomatic, latent or transient. Various factors, especially immunosuppression, increase the persistence and severity of infections, and can promote progression to cancer. (7) The DNA of some highly carcinogenic HPV genotypes (especially HPV-16 and HPV-18) is present in 95% to 100% of cervical epidermoid tumours. Malignant transformation of lesions due to HPV seems to be facilitated by HPV persistence, a high HPV viral load in the cervix, and immunosuppression. (8) However, HPV infection rarely leads to progression to cancer. Only a minority of infections persist for several years, and only about 10% of low-grade lesions progress to a higher grade. About 5% of high-grade lesions progress to invasive cancer. (9) Other anogenital cancers, such as cancer of the anus, vulva, vagina and penis, appear to be linked to HPV (usually genotype 16). (10) Skin cancer due to HPV is rare. Some cancers of the respiratory and gastrointestinal tracts appear to be linked to HPV infection.