title: Ongoing HIV-1 transmission among men who have sex with men in Amsterdam: a 25-year prospective cohort study.
abstract: BACKGROUND
  To examine the suggested resurgence of the HIV epidemic among men who have sex with men (MSM), we studied trends in HIV-1 incidence rates, sexual risk behaviour, risk factors for HIV-1 seroconversion, and source of HIV-1 infection among MSM in the Amsterdam Cohort Studies from 1984 to 2009.
  
  
  METHODS
  Trends in HIV-1 incidence and risk factors for HIV-1 infection were studied using Poisson regression. Trends in sexual risk behaviour were evaluated using logistic regression, correcting for intra-individual correlation via generalized estimating equations. Trends in the source of HIV-1 infection were modelled via logistic regression.
  
  
  RESULTS
  Of 1642 HIV-1-negative individuals, 217 seroconverted during follow-up. HIV-1 incidence rates strongly decreased from 8.6/100 person-years in 1985 to 1.3/100 person-years in 1992; remained relatively stable around 1.0/100 person-years between 1992 and 1996, and slowly increased to 2.0/100 person-years in 2009 (P = 0.14; linear trend 1996-2009). Reports of unprotected anal intercourse (UAI) increased significantly from 1996 onwards. HIV-1 seroconversion was associated with receptive UAI with casual partners, more than five sexual partners, a history of gonorrhoea (all in the preceding 6 months), and a lower educational level. Currently, MSM are more likely to have contracted HIV-1 from casual partners than from steady partners, but trends of recent years suggest that steady partners became a growing source with increasing age.
  
  
  CONCLUSIONS
  Following increases in sexual risk behaviour from 1996 onwards, HIV-1 continues to spread among MSM. Targeted prevention messages should continue to focus on sexual behaviour with casual partners, but also on sexual behaviour within steady relationships.
authors.affiliation: Public Health Service of Amsterdam, Cluster of Infectious Diseases, Department of Research, The Netherlands.
authors.forename: Irálice A V
authors.initials: IA
authors.lastname: Jansen
authors.forename: Ronald B
authors.initials: RB
authors.lastname: Geskus
authors.forename: Udi
authors.initials: U
authors.lastname: Davidovich
authors.forename: Suzanne
authors.initials: S
authors.lastname: Jurriaans
authors.forename: Roel A
authors.initials: RA
authors.lastname: Coutinho
authors.forename: Maria
authors.initials: M
authors.lastname: Prins
authors.forename: Ineke G
authors.initials: IG
authors.lastname: Stolte
mesh_terms: D000328:Adult; D015331:Cohort Studies; D006679:HIV Seropositivity / Q000453:epidemiology* / Q000276:immunology / Q000635:transmission; D015497:HIV-1; D018451:Homosexuality, Male / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D008297:Male; D009426:Netherlands / Q000453:epidemiology; D011446:Prospective Studies; D012307:Risk Factors; D012309:Risk-Taking; D012747:Sexual Partners; D011795:Surveys and Questionnaires