1. Department of Virology, Karolinska Institute, Stockholm, Sweden
2. Department of Pediatric Haematology and Oncology, Children's Hospital and Medical Centre, Seattle, WA, USA
3. Department of Paediatrics, University of Turin, Turin
4. Department of Paediatrics, II University of Rome ‘Tor Vergata’, Rome, Italy
5. Department of Immunology, Karolinska Institute, Stockholm
6. Department of Virology, National Bacteriological Laboratory, Stockholm, Sweden
7. Department of Paediatrics, Catholic University, Rome, Italy