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 SyndromeToxoplasmosisHIV-1ToxocaraAIDS SerodiagnosisHerpesvirus 2, HumanCase-Control StudiesBlood DonorsHepatitis CRural PopulationNeosporaPapillomavirus InfectionsAge FactorsBrazilCytomegalovirusSyphilisImmunoglobulin AHerpes GenitalisToxoplasmaHomosexualityImmunoglobulin MCohort StudiesHuman papillomavirus 16