[1] Univ Iceland, Fac Med, Reykjavik, Iceland
[2] Directorate Hlth Chief Epidemiologist, Reykjavik, Iceland
[3] Univ Iceland, Social Sci Res Inst, Reykjavik, Iceland
[4] Landspitali Univ Hosp, Dept Microbiol, IS-101 Reykjavik, Iceland
[5] Landspitali Univ Hosp, Childrens Hosp Iceland, IS-101 Reykjavik, Iceland