1. From the Department of Pediatrics, Izaak Walton Killam Grace Health Centre and Dalhousie University, Halifax, Nova Scotia;
2. Clinical Epidemiology Unit, The Hospital for Sick Children and University of Toronto, Toronto, Ontario;
3. Department of Pediatrics, Winnipeg Children's Hospital and University of Manitoba, Winnipeg, Manitoba;
4. Department of Pediatrics, Children's Hospital of Eastern Ontario and University of Ottawa, Ottawa, Ontario;
5. Department of Pediatrics, Alberta Children's Hospital and University of Calgary, Calgary, Alberta;
6. Department of Microbiology, Montreal Children's Hospital and McGill University, Montreal, Quebec;
7. Department of Pediatrics, Centre Hôpitalier de l'Université Laval and l'Université Laval, Laval, Quebec; and
8. Department of Pediatrics, British Columbia Children's Hospital and University of British Columbia, Vancouver, British Columbia.