An Efficacy and Safety Study of Grazoprevir (MK-5172) + Elbasvir (MK-8742) in the Treatment of Chronic Hepatitis C Virus in Participants Who Are Co-Infected With Human Immunodeficiency Virus:C-EDGE CO-INFXN (MK-5172-061)

Inclusion Criteria: * Documented chronic HCV genotype (GT) 1, GT4, or GT6 infection with no evidence of non-typeable or mixed GT infection (positive for anti-HCV antibody, HCV RNA, or any of the listed GTs at least 6 months prior to screening must be confirmed by screening lab results) * Treatment naïve for all anti-HCV treatments * HIV-1 infection documented by laboratory test * Currently naïve to treatment with any antiretroviral therapy (ART) and have no plans to initiate ART during this study OR on a HIV ART for at least 8 weeks prior to study entry * Has not experienced any alteration(s) in HIV therapy within 4 weeks of randomization * Has at least one viable antiretroviral regimen alternative beyond the current regimen in the event of HIV virologic failure or the development of anti-retroviral drug resistance * Participants of reproductive potential must agree to remain abstinent from heterosexual activity OR use (or have their partner use) acceptable contraception during heterosexual activity while receiving study drug and for 14 days after last dose of study drug. Exclusion Criteria: * Evidence of decompensated liver disease manifested by the presence or history of ascites, esophageal or gastric variceal bleeding, hepatic encephalopathy or other signs of symptoms of advanced liver disease * Co-infected with hepatitis B virus * History of malignancy \<=5 years prior to study start except for adequately treated basal cell or squamous cell skin cancer or in situ cervical cancer or is under evaluation for other active or suspected malignancy * Taking or planning to take any HIV therapy that includes a ritonavir-boosted or unboosted protease inhibitor, efavirenz or etravirine * Currently participating or has participated in a study with an investigational compound within 30 days of study start and is not willing to refrain from participating in another study during this study * Clinically-relevant drug or alcohol abuse within 12 months of study start * Pregnant, breast feeding, or expecting to conceive or donate eggs from Day 1 of the study throughout treatment and 14 days after the last dose of study medication, or longer if dictated by local regulations * Organ transplants (including hematopoietic stem cell transplants) other than cornea and hair * Poor venous access * History of gastric surgery (e.g., stapling, bypass) or history of malabsorption disorders (e.g., celiac sprue disease) * Medical condition requiring, or likely to require, chronic systemic administration of corticosteroids during this study * History of opportunistic infection in the 6 months prior to study start * Use of HIV drugs other than a dual nucleoside reverse transcriptase inhibitor (NRTI) backbone of tenofovir or abacavir and either emtricitibine or lamivudine PLUS raltegravir (or dolutegravir or rilpivirine)