1. Institute of Clinical Medicine; University of Oslo; Oslo Norway
2. Division of Women and Children; Oslo University Hospital; Oslo Norway
3. Department of Virology; Norwegian Institute of Public Health; Oslo Norway
4. Oslo Centre for Biostatistics and Epidemiology; Research Support Services; Oslo University Hospital; Oslo Norway
5. Department of Medical Microbiology St.Olavs Hospital; Trondheim Norway
6. Department of Microbiology; Oslo University Hospital; Oslo Norway
7. Department of Medical Microbiology; Vestre Viken Health Trust; Drammen Norway