title: Modelling the HIV epidemic among MSM in the United Kingdom: quantifying the contributions to HIV transmission to better inform prevention initiatives.
abstract: OBJECTIVE
  HIV is a major public health problem among MSM in the United Kingdom with around 2400 new infections annually. We quantified the contribution of biological and behavioural factors.
  
  
  METHODS
  Modelling study.
  
  
  METHODS
  A partnership-based model of HIV transmission among UK MSM aged 15-64 years was developed and calibrated to time series HIV prevalence. The calibration was validated using multiple surveillance datasets. Population-attributable fractions were used to estimate the contribution of behavioural and biological factors to HIV transmission over the period 2001-2002, 2014-2015, and 2019-2020.
  
  
  RESULTS
  The contribution of most biological and behavioural factors was relatively constant over time, with the key group sustaining HIV transmission being higher-sexual activity MSM aged below 35 years living with undiagnosed HIV. The effect of primary HIV infection was relatively small with 2014-2015 population-attributable fraction of 10% (3-28%) in comparison with other subsequent asymptomatic stages. Diagnosed men who were not on antiretroviral therapy (ART) currently contributed 26% (14-39%) of net infections, whereas ART-treated MSM accounted for 17% (10-24%). A considerable number of new infections are also likely to occur within long-term relationships.
  
  
  CONCLUSIONS
  The majority of the new HIV infections among MSM in the United Kingdom during 2001-2020 is expected to be accounted for by a small group of younger and highly sexually active individuals, living with undiagnosed HIV in the asymptomatic stage. Bringing this group into HIV/AIDS care by improving testing uptake is a vital step for preventing onward transmission and will determine the success of using ART as prevention.
authors: aCentre for the Mathematical Modelling of Infectious Diseases and Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London bMedical Research Council Biostatistics Unit, Cambridge cHIV and STI Department, Public Health England, Colindale dCentre for Sexual Health & HIV Research, Department of Infection & Population Health, Mortimer Market Centre, University College London eSchool of Health Sciences, City University London, London, UK.
authors: Narat
authors: N
authors: Punyacharoensin
authors: William John
authors: WJ
authors: Edmunds
authors: Daniela
authors: D
authors: De Angelis
authors: Valerie
authors: V
authors: Delpech
authors: Graham
authors: G
authors: Hart
authors: Jonathan
authors: J
authors: Elford
authors: Alison
authors: A
authors: Brown
authors: Noel
authors: N
authors: Gill
authors: Richard G
authors: RG
authors: White
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D058070:Asymptomatic Diseases; D018562:Disease Transmission, Infectious; D058872:Epidemics; D015658:HIV Infections / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission*; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D012725:Sexual Behavior; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult