HIV SeropositivityHIV SeroprevalenceHIV InfectionsSubstance Abuse, IntravenousSexual BehaviorRisk FactorsSeroepidemiologic StudiesAntibodies, ViralAntibodies, BacterialChlamydophila pneumoniaeImmunoglobulin GChlamydophila InfectionsSerologic TestsEnzyme-Linked Immunosorbent AssayHIV SeronegativityPrevalenceHelicobacter pyloriHelicobacter InfectionsToxocariasisAntibodies, ProtozoanCytomegalovirus InfectionsAcquired Immunodeficiency SyndromeHIV-1ToxoplasmosisCross-Sectional StudiesHerpesvirus 2, HumanToxocaraAIDS SerodiagnosisBlood DonorsHepatitis CCase-Control StudiesNeosporaPapillomavirus InfectionsCytomegalovirusRural PopulationBrazilToxoplasmaSyphilisHerpes GenitalisImmunoglobulin AHomosexualityAge FactorsAntibodies, HelminthImmunoglobulin M