HIV SeropositivityHIV SeroprevalenceHIV InfectionsSubstance Abuse, IntravenousSexual BehaviorDiscrimination (Psychology)Risk FactorsSeroepidemiologic StudiesDiscrimination LearningPrejudiceSocial DiscriminationAntibodies, ViralPitch DiscriminationAntibodies, BacterialChlamydophila pneumoniaeImmunoglobulin GChlamydophila InfectionsPrevalenceSerologic TestsPrimary PreventionEnzyme-Linked Immunosorbent AssayHIV SeronegativityCross-Sectional StudiesHelicobacter pyloriHelicobacter InfectionsSensory ThresholdsRacismAcquired Immunodeficiency SyndromeToxocariasisCytomegalovirus InfectionsAntibodies, ProtozoanUnited StatesCase-Control StudiesAIDS SerodiagnosisCenters for Disease Control and Prevention (U.S.)Age FactorsHomosexuality, MaleHIV-1ToxoplasmosisTime FactorsHerpesvirus 2, HumanRural PopulationRisk-TakingToxocaraProspective StudiesHepatitis CCohort StudiesSecondary PreventionBlood DonorsLogistic ModelsBrazilPapillomavirus InfectionsSexual PartnersPattern Recognition, VisualIncidenceOdds RatioDifferential ThresholdQuestionnairesHomosexualitySyphilisNeosporaPhotic StimulationColor PerceptionHerpes GenitalisDiscriminant AnalysisCytomegalovirusPregnancySensitivity and SpecificitySocioeconomic FactorsAnti-HIV AgentsImmunoglobulin AToxoplasmaIndiaOdorsHepatitis A Virus, HumanHepatitis ASpeech Discrimination TestsHuman papillomavirus 16Immunoglobulin MMultivariate AnalysisHepatitis BProstitutionSmell