title: Epidemiologic and evolutionary trends of HIV-1 CRF31_BC-related strains in southern Brazil.
abstract: BACKGROUND
  To evaluate the impact of HIV-1 CRF31_BC in the southern Brazilian HIV epidemic.
  
  
  METHODS
  Blood plasma from 284 patients was collected from July 2002 to January 2003 at 2 reference HIV/AIDS centers in southern Brazil. Viral protease and reverse transcriptase (RT) genomic regions were amplified by RT polymerase chain reaction, sequenced, and subtyped. Evolutionary analyses were performed to estimate the CRF31_BC most recent common ancestor and its population growth rate with BEAST version 1.3.
  
  
  RESULTS
  CRF31_BC was responsible for 7.4% of infections. The average time of HIV diagnosis and the proportion of patients on antiretroviral treatment were shorter for CRF31_BC and subtype C than for subtype B. CRF31_BC was found as early as in 1990 in the Brazilian epidemic. Evolutionary analysis of CRF31_BC revealed that it appeared immediately after the introduction of subtype C in Brazil and has been growing at a similar rate as subtype C.
  
  
  CONCLUSIONS
  CRF31_BC plays an important role in the HIV epidemic of southern Brazil, and its prevalence has increased throughout the years. This circulating recombinant form corresponds to approximately 25% of total HIV isolates in this region in 2004. Understanding the cause of this spread is important for public health strategies in Brazil and in Latin America.
authors.affiliation: Departamento de Genética, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, and Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: André F
authors.initials: AF
authors.lastname: Santos
authors.forename: Carlos G
authors.initials: CG
authors.lastname: Schrago
authors.forename: Ana Maria B
authors.initials: AM
authors.lastname: Martinez
authors.forename: Raul
authors.initials: R
authors.lastname: Mendoza-Sassi
authors.forename: Jussara
authors.initials: J
authors.lastname: Silveira
authors.forename: Thatiana M
authors.initials: TM
authors.lastname: Sousa
authors.forename: Renan B
authors.initials: RB
authors.lastname: Lengruber
authors.forename: Esmeralda A J M
authors.initials: EA
authors.lastname: Soares
authors.forename: Eduardo
authors.initials: E
authors.lastname: Sprinz
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Soares
mesh_terms: D000328:Adult; D001938:Brazil / Q000453:epidemiology; D004196:Disease Outbreaks; D019143:Evolution, Molecular; D005260:Female; D015658:HIV Infections / Q000453:epidemiology*; D016333:HIV Protease / Q000235:genetics; D054303:HIV Reverse Transcriptase / Q000235:genetics; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D008297:Male; D017720:Molecular Epidemiology
chemical_list: D054303:HIV Reverse Transcriptase; D016333:HIV Protease