1. From the Danish Epidemiology Science Centre at the Department of Epidemiology and Social Medicine, University of Aarhus,
2. Medical Research Unit, Ringkjøbing County,
3. Department of Clinical Epidemiology at Aalborg Hospital and University of Aarhus, Aarhus;
4. Department of Clinical Microbiology, Aalborg Hospital, Aalborg; and the
5. Department of Medicine V, Aarhus University Hospital, Aarhus C, Denmark.