This study is a survey in Japan of Maribavir tablets used to treat participants with Cytomegalovirus (CMV) infection refractory to existing anti-CMV therapy in organ transplantation (including hematopoietic stem cell transplantation). The main aim of the study is to check if treatment with Maribavir can protect Japanese people against CMV infection, and to check side effect from the study treatment. The study sponsor will not be involved in how the participants are treated but will provide instructions on how the clinics will record what happens during the study. During the study, participants with CMV infection will take Maribavir tablets according to their clinic's standard practice. The study doctors will check for side effects from Maribavir tablets for 27 weeks.