A largescale study conducted in two parts of the world has revealed that roughly one in four heterosexual men [emphasis added] have anal human papillomavirus (HPV) infection. … “There are a number of questions this study raises. For instance, how was HPV transmitted to the perianal region and anal canal of these men.” How indeed?
—from the Gay and Lesbian Review's blog.
For the nitty gritty (of the statistical as opposed to the anecdotal variety) see the full report in the Journal of Infectious Diseases.