HIV SeropositivityHIV SeroprevalenceHIV InfectionsSubstance Abuse, IntravenousSexual BehaviorRisk FactorsDisease ProgressionSeroepidemiologic StudiesAntibodies, ViralAntibodies, BacterialChlamydophila pneumoniaeImmunoglobulin GChlamydophila InfectionsEnzyme-Linked Immunosorbent AssaySerologic TestsHIV SeronegativityPrevalenceHelicobacter pyloriHelicobacter InfectionsAge FactorsAcquired Immunodeficiency SyndromeToxocariasisCross-Sectional StudiesHIV-1Antibodies, ProtozoanCytomegalovirus InfectionsCohort StudiesCase-Control StudiesToxoplasmosisTime FactorsHepatitis CHerpesvirus 2, HumanProspective StudiesToxocaraAIDS SerodiagnosisBlood DonorsPapillomavirus InfectionsRural PopulationNeosporaCD4 Lymphocyte CountFollow-Up StudiesCytomegalovirusImmunoglobulin AHerpes GenitalisOdds RatioSyphilisHuman papillomavirus 16HomosexualityRisk-TakingHomosexuality, MaleBrazilToxoplasmaCell CycleSexual PartnersImmunoglobulin MHepatitis A Virus, HumanIncidenceHepatitis AMultivariate Analysis