Determinants of Human Immunodeficiency Virus (HIV) prevalence in homosexual and bisexual men screened for admission to a cohort study of HIV negatives in Belo Horizonte, Brazil: Project Horizonte Leia mais sobre Determinants of Human Immunodeficiency Virus (HIV) prevalence in homosexual and bisexual men screened for admission to a cohort study of HIV negatives in Belo Horizonte, Brazil: Project Horizonte