Observational Trial to Evaluate Hematopoietic Stem Cell Transplantation CMV Reactivation

Inclusion Criteria: 1. Age ≥18 years. 2. Patients who will undergo one of the following types of allogeneic transplantation: matched related donor, matched or mismatched unrelated donor, haploidentical, or cord blood. 3. Patients must be seropositive for CMV prior to transplantation, regardless of donor seropositivity. 4. Institutional Review Board (IRB)-approved written Informed Consent and privacy agreement per national regulation (e.g., Health Insurance Portability and Accountability Act \[HIPAA\] for sites in the USA) must be obtained from the patient or the patient's legally authorized representative prior to any study-specific procedures. 5. Patients must be considered suitable for the study by the Investigator. Exclusion Criteria: * 1\. Patients with a known active CMV reactivation within 1 month prior to enrollment or during the study's pre-transplant screening period. 2\. Patients who have received any antiviral therapy active against CMV other than acyclovir and valacyclovir (i.e., foscarnet, ganciclovir, valganciclovir, or cidofovir) during the month prior to enrollment. 3\. Patients who have previously received or are planning to receive a CMV vaccine. 4\. Patients who are known to be hepatitis B, hepatitis C, or human immunodeficiency virus (HIV) positive. 5\. Patients who are known to have a clinically significant medical or psychiatric condition considered a high risk for participation in an investigational study. 6\. Patients who are participating in or plan to participate in CMV-related drug or vaccine studies.