Background. We report on the hepatitis C virus(HCV) epidemic among HIV-positive men who have sex with men(MSM) in the UK and model its trajectory with or without scaled-up HCV direct-acting antivirals(DAAs).

Methods. A dynamic HCV transmission model among HIV-diagnosed MSM in the UK was calibrated to HCV prevalence(Ab+ or RNA+), incidence, and treatment from 2004-2011 among HIV-diagnosed MSM in the UK collaborative HIV cohort(UK CHIC). The epidemic was projected with: current or scaled-up HCV treatment, with or without a 20% behavioral risk reduction.

Results. HCV prevalence among HIV-positive MSM in UK CHIC increased from 7.3% in 2004 to 9.9% in 2011, whereas primary incidence was flat(1.02-1.38 per 100 person-years). Over the next decade, modelling suggests 94% of infections are attributable to high-risk individuals, comprising 7% of the population. Without treatment, HCV chronic prevalence could have been 38% higher in 2015(11.9% vs 8.6%). With current treatment and SVR rates(status quo), chronic prevalence is likely to increase to 11% by 2025, but stabilize with DAA introduction in 2015. With DAAs scale-up to 80% within one year of diagnosis (regardless of disease stage), 20%/yr thereafter, chronic prevalence could reduce by 71% (to 3.2%) compared to status quo in 2025. With additional behavioural interventions, chronic prevalence could reduce further to <2.5% by 2025.

Conclusions. Epidemiological data and modelling suggest a continuing HCV epidemic among HIV-diagnosed MSM in the UK driven by high-risk individuals, despite high treatment rates. Substantial reductions in HCV transmission could be achieved through scale-up of DAAs and moderately effective behavioural interventions.