Inclusion criteria:  Allogeneic transplant with any cells source and conditioning regimen Age between 0-21 years Viral infection/reactivation (CMV, EBV, ADV) Resistance of viral infections to treatments Absence of concomitant severe uncontrolled infections Life expectancy exceeding 30 days Absence of acute or chronic uncontrolled Graft versus Host Disease (GvHD) Absence of acute kidney damage (creatinine value> 3 times the value normal with respect to age) not related to viral infection; Absence of severe acute liver injury (direct bilirubin> 3mg / dl or glutamic-oxaloacetic transaminase -SGOT> 500 UI/L) not related to viral infection; Presence of informed consent to the treatment of the patient / parent /legal guardian.  Exclusion Criteria:  Absence of a suitable donor (seronegativity for the virus in question and / or failure to respond to the secretion test) Patient with severe renal and/or hepatic impairment as specified above Primary or secondary graft failure Relapse of malignant underlying disease