This is a multi-part study to evaluate the safety, tolerability, and pharmacokinetics (PK) of uprifosbuvir (MK-3682/IDX21437) in healthy participants and in participants infected with HCV genotype (GT)1-GT6. The effect of food on the PK of uprifosbuvir will be evaluated. The antiviral activity of uprifosbuvir will also be assessed in HCV-infected participants.