Risk of Human Papillomavirus Infection and Associated Cancer

130 Infection with human papillomavirus (HPV) poses risk of cervical and anal cancer in women and anal cancer in men who have sex with men (MSM). There are high rates of cervical and anal HPV infection in HIV-infected women and high rates of anal HPV infection in HIV-infected MSM. Infection in the cervix primarily occurs in the transformation zone where the squamous epithelium of the exocervix and columnar epithelium of the endocervix meet. The anal canal has a similar zone where the squamous epithelium of the anus meets the columnar epithelium of the rectum. This latter structure is more exteriorized in women than in men, which may account for the apparent higher rate of anal infection in women than in men. The virus must reach the basal cell layer to initiate infection, and it is currently thought that it takes approximately 24 hours for the virus to enter these cells. This window appears to allow time for vaccine-induced antibody response that has been shown to be effective in preventing infection (see below). Risk of Human Papillomavirus Infection and Associated Cancer