1. Microbiology and Tumor Biology Center, Karolinska Institute, SE-171 77 Stockholm, Sweden. 2Unit of Neonatology, Astrid Lindgren's Hospital, Karolinska Hospital, SE-171 77 Stockholm, Sweden
2. Institut Pasteur, Dé
3. Centre Pasteur du Cameroun, BP 1274 Yaoundé
4. Microbiology and Tumor Biology Center, Karolinska Institute, SE-171 77 Stockholm, Sweden. 2Unit of Neonatology, Astrid Lindgren's Hospital, Karolinska Hospital, SE-171 77 Stockholm, Sweden
5. Department of Clinical Virology, IMPI, Karolinska Institute, Huddinge University Hospital, SE-141 86 Huddinge/Stockholm, Sweden. 6INSERM U131, 92140 Clamart, France