title: Transmission of Non-B HIV Subtypes in the United Kingdom Is Increasingly Driven by Large Non-Heterosexual Transmission Clusters.
abstract: BACKGROUND
  The United Kingdom human immunodeficiency virus (HIV) epidemic was historically dominated by HIV subtype B transmission among men who have sex with men (MSM). Now 50% of diagnoses and prevalent infections are among heterosexual individuals and mainly involve non-B subtypes. Between 2002 and 2010, the prevalence of non-B diagnoses among MSM increased from 5.4% to 17%, and this study focused on the drivers of this change.
  
  
  METHODS
  Growth between 2007 and 2009 in transmission clusters among 14 000 subtype A1, C, D, and G sequences from the United Kingdom HIV Drug Resistance Database was analysed by risk group.
  
  
  RESULTS
  Of 1148 clusters containing at least 2 sequences in 2007, >75% were pairs and >90% were heterosexual. Most clusters (71.4%) did not grow during the study period. Growth was significantly lower for small clusters and higher for clusters of ≥7 sequences, with the highest growth observed for clusters comprising sequences from MSM and people who inject drugs (PWID). Risk group (P< .0001), cluster size (P< .0001), and subtype (P< .01) were predictive of growth in a generalized linear model.
  
  
  CONCLUSIONS
  Despite the increase in non-B subtypes associated with heterosexual transmission, MSM and PWID are at risk for non-B infections. Crossover of subtype C from heterosexuals to MSM has led to the expansion of this subtype within the United Kingdom.
authors.affiliation: Institute for Evolutionary Biology.
authors.forename: Manon
authors.initials: M
authors.lastname: Ragonnet-Cronin
authors.affiliation: Roslin Institute, University of Edinburgh, Edinburgh.
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: Lycett
authors.affiliation: Institute for Evolutionary Biology.
authors.forename: Emma B
authors.initials: EB
authors.lastname: Hodcroft
authors.affiliation: London School of Hygiene and Tropical Medicine.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Hué
authors.affiliation: MRC Clinical Trials Unit at University College London.
authors.forename: Esther
authors.initials: E
authors.lastname: Fearnhill
authors.affiliation: Public Health England, London, United Kingdom.
authors.forename: Alison E
authors.initials: AE
authors.lastname: Brown
authors.affiliation: Public Health England, London, United Kingdom.
authors.forename: Valerie
authors.initials: V
authors.lastname: Delpech
authors.affiliation: MRC Clinical Trials Unit at University College London.
authors.forename: David
authors.initials: D
authors.lastname: Dunn
authors.affiliation: Institute for Evolutionary Biology.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Leigh Brown
mesh_terms: D016000:Cluster Analysis; D015658:HIV Infections / Q000453:epidemiology / Q000635:transmission* / Q000821:virology*; D015497:HIV-1 / Q000235:genetics*; D018451:Homosexuality, Male / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D008297:Male; D017720:Molecular Epidemiology; D010802:Phylogeny; D006113:United Kingdom / Q000453:epidemiology
keywords: HIV; MSM; PWID; clusters; crossover; epidemiology; heterosexual; phylogenetics; phylogeny; subtypes