HIV SeropositivityHIV SeroprevalenceHIV InfectionsSubstance Abuse, IntravenousSexual BehaviorRisk FactorsSeroepidemiologic StudiesAntibodies, ViralAntibodies, BacterialChlamydophila pneumoniaeImmunoglobulin GChlamydophila InfectionsSerologic TestsEnzyme-Linked Immunosorbent AssayHIV SeronegativityPrevalenceHelicobacter pyloriHelicobacter InfectionsToxocariasisAntibodies, ProtozoanCross-Sectional StudiesCytomegalovirus InfectionsAcquired Immunodeficiency SyndromeToxoplasmosisToxocaraHIV-1Herpesvirus 2, HumanAIDS SerodiagnosisBlood DonorsCase-Control StudiesHepatitis CNeosporaPapillomavirus InfectionsRural PopulationAge FactorsSyphilisCytomegalovirusBrazilHerpes GenitalisToxoplasmaImmunoglobulin AHomosexualityOdds RatioCohort Studies