1. Department of Infectious Disease, Oslo University Hospital, Oslo, Norway;
2. Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway;
3. Department of Respiratory Medicine, Oslo University Hospital, Oslo, Norway;
4. Faculty of Odontology, University of Oslo, Oslo, Norway;
5. Oslo Group of Biostatistics and Epidemiology, Oslo University Hospital, Oslo, Norway;
6. Department of Infection Control and Environmental Health, Norwegian Institute of Public Health, Oslo, Norway;
7. Department of Internal Medicine, Lovisenberg Hospital, Oslo, Norway