Inclusion Criteria  Be Japanese with Japanese nationality, >=16 years of age at the time of consent. Be a recipient of HSCT or SOT that is functioning at the time of Screening. Have a documented CMV infection with a screening value of >455 IU/mL in plasma in 2 consecutive assessments, separated by at least 1 day, as determined by a central specialty laboratory qPCR or comparable quantitative CMV DNA results. Both samples should be taken within 14 days prior to first dose of study treatment with the second sample obtained within 5 days prior to first dose of study treatment at Visit 2/Day 0.  Have the current CMV infection after HSCT or SOT, either primary or reactivation, which, in the investigator's opinion, requires treatment and have any of the following.  Asymptomatic participants: The subjects do not have CMV tissue-invasive disease or CMV syndrome (SOT subjects only) at Baseline, as determined by the investigator according to the criteria specified by Ljungman et al., 2017. Refractory or resistant participants: The participant must have a current CMV infection that is refractory to the most recently administered of the anti-CMV treatment agent(s). Refractory is defined as documented failure to achieve >1 log10 (common logarithm to base 10) decrease in CMV DNA level in plasma after a 14 day or longer treatment period with IV ganciclovir/oral valganciclovir, or IV foscarnet.  Have all of the following results as part of screening laboratory assessments (results from either the central laboratory or a local laboratory can be used for qualification):  Absolute neutrophil count >=1,000/mm^3 (1.0 × 10^9/L) Platelet count >=25,000/mm^3 (25 × 10^9/L) Hemoglobin >=8 g/dL Estimated creatinine clearance >=30 mL/minute (estimated glomerular filtration rate by Modification of Diet in Renal Disease) Be able to swallow tablets. Have life expectancy of >=8 weeks. Weigh >=40 kg.  Exclusion Criteria  Have central nervous system (CNS) CMV tissue-invasive disease or CMV retinitis as assessed by the investigator at the time of Screening and prior to administration at Visit 2/Day 0.  Be receiving valganciclovir, ganciclovir, foscarnet, or letermovir when study treatment is initiated, or anticipated to require 1 of these agents during the 8-week treatment period.  NOTE: Participants receiving letermovir must discontinue 3 days prior to first dose of study treatment. Ganciclovir, valganciclovir, and foscarnet must be discontinued prior to the first dose of study treatment.  Have known hypersensitivity to the active substance or to an excipient of the study treatments. Have severe vomiting, diarrhea, or other severe GI illness within 24 hours prior to the first dose of study treatment that would preclude administration of oral medication. Require mechanical ventilation or vasopressors for hemodynamic support at the time of Baseline. Pregnant or nursing female. Have received any investigational agent (including CMV-specific T-cells) with known anti-CMV activity within 30 days before initiation of the study treatment at any time. Have previously received maribavir. Have serum aspartate aminotransferase (AST) >5 times upper limit of normal (ULN) at Screening, or serum alanine aminotransferase (ALT) >5 times ULN at Screening, or total bilirubin >=3.0* ULN at Screening (except for documented Gilbert's syndrome), as analyzed by local or central laboratory. Have known (previously documented) positive results for HIV. Participants must have a confirmed negative HIV test result within 3 months of study entry or, if unavailable, be tested by a local laboratory during the screening period. Have active malignancy with the exception of nonmelanoma skin cancer, as determined by the investigator. Participants who experience relapse or progression of their underlying malignancy (for which HSCT or SOT was performed), as determined by the investigator, are not to be enrolled. Be undergoing treatment for acute or chronic hepatitis C.