This is a randomized, parallel-group, placebo-controlled, multi-site, multinational, double-blind followed by open label period, Phase 3 trial of 100 mg of grazoprevir (MK-5172) in combination with 50 mg of elbasvir (MK-8742) (grazoprevir/elbasvir fixed-dose combination [FDC]) in treatment-naïve (TN) participants with chronic hepatitis C virus (HCV), genotype (GT) 1, 4 or 6 infection. The primary hypothesis is that the percentage of participants receiving grazoprevir/elbasvir FDC in the Immediate Treatment Group (ITG) achieving Sustained Virologic Response 12 weeks after the end of all study therapy (SVR12) will be superior to the historical reference rate of 73%.