[1] Univ Uppsala Hosp, Dept Family Med, Uppsala, Sweden
[2] Lindesberg Hosp, Dept Otorhinolaryngol Head & Neck Surg, Lindesberg, Sweden
[3] Huddinge Univ Hosp, Dept Pathol & Cytol, S-14186 Huddinge, Sweden
[4] Gavle Sandviken Cent Hosp, Dept Clin Microbiol, Gavle, Sweden
[5] Univ Uppsala Hosp, Dept Clin Microbiol, Uppsala, Sweden
[6] Univ Uppsala Hosp, Dept Infect Dis, S-75185 Uppsala, Sweden
[7] Natl Publ Hlth Inst, Oulu, Finland