1. Department of Clinical Microbiology, Microbiology and Tumor Biology Center
2. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet
3. Unit of Infectious Diseases
4. Division of Pediatrics, Department of Clinical Sciences, Huddinge University Hospital, Stockholm, Sweden
5. Unit of Gastroenterology and Hepatology, Department of Medicine, Karolinska Hospital
6. The Swedish Institute for Infectious Disease Control