1. Department of Clinical Sciences; Division of Otorhinolaryngology; Umeå University; Umeå Sweden
2. Department of Clinical Microbiology; Division of Clinical Immunology; Umeå University; Umeå Sweden
3. Department of Surgical Sciences; Division of Otorhinolaryngology; Uppsala University; Uppsala Sweden
4. Department of Medical Bioscience; Division of Pathology; Umeå University; Umeå Sweden