The development of fever, splenomegaly, atypical lymphocytosis, abnormal liver function tests, and, occasionally, a skin rash that develops following blood transfusion or perfusion of an organ during surgery. The syndrome appears 3 to 5 weeks after transfusion or perfusion with fresh (less than 24 hr old) blood, usually in large quantities. The causative agent is thought to be cytomegalovirus.