Epstein-Barr Virus Infections/pathology; Heart Transplantation; Heart-Lung Transplantation; Intestines/pathology; Lung Transplantation; Lymphoproliferative Disorders/pathology; Postoperative Complications/pathology; Adolescent; Age Factors; Child; Child, Preschool; Disease Transmission, Infectious; Epstein-Barr Virus Infections/etiology; Epstein-Barr Virus Infections/transmission; Female; Heart Transplantation/adverse effects; Heart-Lung Transplantation/adverse effects; Humans; Immunocompromised Host; Immunosuppressive Agents/adverse effects; Immunosuppressive Agents/therapeutic use; Infant; Intestinal Perforation/etiology; Intestinal Perforation/surgery; Intestines/surgery; Intussusception/etiology; Intussusception/surgery; Lung Transplantation/adverse effects; Lymphoproliferative Disorders/drug therapy; Lymphoproliferative Disorders/etiology; Lymphoproliferative Disorders/mortality; Male; Postoperative Complications/drug therapy; Postoperative Complications/etiology; Postoperative Complications/mortality; Postoperative Complications/surgery; Retrospective Studies