[1] Orebro Univ Hosp, Dept Infect Dis, SE-70185 Orebro, Sweden
[2] Swedish Inst Infect Dis Control, Dept Epidemiol, Solna, Sweden
[3] Karolinska Univ Hosp, Karolinska Inst, Dept Gastroenterol & Hepatol, Stockholm, Sweden
[4] Univ Orebro, Dept Clin Med, Orebro, Sweden
[5] Karolinska Inst, Dept Med Epidemiol & Biostat, Stockholm, Sweden
[6] European Ctr Dis Prevent & Control ECDC, Stockholm, Sweden
[7] Karolinska Univ Hosp, Karolinska Inst, Dept Med, Clin Epidemiol Unit, Stockholm, Sweden