1 Division of Pediatric Hematology and Oncology, Oulu University Hospital, Oulu, Finland.
2 University of Helsinki, Helsinki, Finland.
3 Division of Hematology-Oncology and Stem Cell Transplantation, New Children's Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
4 HUS Diagnostic Center, HUSLAB, Clinical Microbiology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
5 Department of Virology and Immunology, Helsinki University Hospital and University of Helsinki, Helsinki, Finland.