Prevalence of Active <scp>HCV</scp> Infection in Spain in 2022 Using Multiparameter Evidence Synthesis

Hepatitis C virus (HCV) remains a major public health concern worldwide. Spain has implemented large-scale direct-acting antiviral (DAA) treatment programs, yet the prevalence of active HCV infection (aHCV) and its trends over time remain incompletely characterised. We applied Bayesian multiparameter evidence synthesis (MPES) to estimate the prevalence of aHCV in Spain in 2022 and its change from 2019 to 2022. The Spanish population aged 15-79 years was stratified into four non-overlapping risk groups: current people who inject drugs (PWID), ex-PWID, gay-bisexual and other men who have sex with men (GBMSM) engaging in chemsex (GBMSMchem), and the general population. Data sources included, among others, national seroprevalence surveys, behavioural studies, national databases, and clinical records on DAA treatment outcomes. The estimated overall aHCV prevalence in Spain in 2022 was 0.14% (95% Credible Interval: 0.05%-0.27%), corresponding to approximately 54,500 individuals. Prevalence was highest among current PWID (12.5%) and GBMSMchem (8.4%). Compared to 2019, the total number of aHCV cases declined by ~20,000, largely attributable to DAA treatment. Among the general population, 29.4% of aHCV cases remained undiagnosed, with the highest prevalence in individuals aged 50-59 (0.25%) and 60-69 (0.16%) years. Spain has made substantial progress towards HCV elimination, but key populations such as PWID and GBMSMchem remain at high risk. Targeted interventions, including expanded harm reduction services and accessible HCV testing and treatment, are essential to achieving the World Health Organization (WHO) elimination targets by 2030.