Epidemic history and baseline resistance to NS5A-specific direct acting drugs of hepatitis C virus in Spain.

Hepatitis C virus (HCV) infection remains a global health problem. Previously, the prevalence of NS5A resistance-associated substitutions (RASs) to elbasvir, a new direct-acting antiviral (DAA) against the NS5A viral protein was assessed by our group before its introduction into clinical use in Spain. However, the origin, epidemic history, transmission dynamics, diversity and baseline RASs to NS5A direct-acting agents of HCV-GT1a in Spain remain unknown. A nationwide cross-sectional survey of individuals chronically-infected with HCV-G1a and DAAs-naïve was performed. HCV population sequencing, phylogenetic analysis and Bayesian methods were used. GT1a clade II was more prevalent than clade I (82.3% vs. 17.7%; P < 0.001) and older (estimated origin in 1912 vs. 1952). Clade II epidemic is currently declining whereas clade I epidemic has reached equilibrium. A total of 58 single RASs were identified, which account for the moderate level (10%) of baseline resistance observed. When considering the regional data, marked differences were observed, with thirteen regions showing an intermediate level (5-15%) and one a high level (20%) of resistance. Current HCV-GT1a epidemic in Spain is driven by clade I which seem to have different dissemination routes relative to clade II. A moderate level of baseline RASs to NS5A-DAAs with marked differences among regions was observed. Close surveillance of response to treatment with DAAs will be important.