title: Transmission networks of HIV-1 among men having sex with men in the Netherlands.
abstract: OBJECTIVE
  To obtain insight in the HIV-1 transmission networks among men having sex with men (MSM) in the Netherlands.
  
  
  METHODS
  A phylogenetic tree was constructed from polymerase sequences isolated from 2877 HIV-1 subtype B-infected patients monitored as part of the AIDS Therapy Evaluation in the Netherlands (ATHENA) nationwide observational cohort.
  
  
  METHODS
  For MSM with a known date of infection, the most similar sequences were selected as potential transmission pairs when they clustered with bootstrap value of at least 99%. Time from infection to onward transmission was estimated as the median time between dates of infection for each transmission pair. The source of infections with a resistant strain was traced using the entire phylogenetic tree.
  
  
  RESULTS
  Of sequences from 403 MSM with a known date of infection between 1987 and 2007, 175 (43%) formed 63 clusters. Median time to onward transmission was 1.4 years (interquartile range 0.6-2.7). Twenty-four (6%) MSM carried a virus with resistance-related mutations, 13 of these were in eight clusters together with sequences from 28 other patients in the entire phylogenetic tree. Six clusters contained sequences obtained from 29 men all presenting the same resistance-related mutations.
  
  
  CONCLUSIONS
  From our selection of likely transmission pairs, we conclude that onward transmission of HIV-1 from infected MSM in the Netherlands happens both during and after primary infection. Transmission of resistant strains from the antiretroviral therapy-treated population is limited, but strains with resistance-related mutations have formed subepidemics.
authors.affiliation: HIV Monitoring Foundation, Academic Medical Centre, Amsterdam, The Netherlands. D.O.Bezemer@amc.uva.nl
authors.forename: Daniela
authors.initials: D
authors.lastname: Bezemer
authors.forename: Ard
authors.initials: A
authors.lastname: van Sighem
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Lukashov
authors.forename: Lia
authors.initials: L
authors.lastname: van der Hoek
authors.forename: Nicole
authors.initials: N
authors.lastname: Back
authors.forename: Rob
authors.initials: R
authors.lastname: Schuurman
authors.forename: Charles A B
authors.initials: CA
authors.lastname: Boucher
authors.forename: Eric C J
authors.initials: EC
authors.lastname: Claas
authors.forename: Maarten C
authors.initials: MC
authors.lastname: Boerlijst
authors.forename: Roel A
authors.initials: RA
authors.lastname: Coutinho
authors.forename: Frank
authors.initials: F
authors.lastname: de Wolf
mesh_terms: D000328:Adult; D001483:Base Sequence; D015153:Blotting, Western; D016000:Cluster Analysis; D024882:Drug Resistance, Viral / Q000235:genetics* / Q000502:physiology; D015751:Genes, pol / Q000235:genetics*; D015658:HIV Infections / Q000235:genetics / Q000635:transmission* / Q000821:virology; D015497:HIV-1 / Q000235:genetics*; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D010802:Phylogeny