1. Departments of Pediatrics, Microbiology and Infectious Diseases, University of Calgary and the Child Health Research Unit, Alberta Children's Hospital, Calgary, Alberta
2. Departments of Pediatrics, Dalhousie University, Halifax, Nova Scotia
3. Community Health and Epidemiology, Dalhousie University, Halifax, Nova Scotia
4. Shared Department of Microbiology, Mount Sinai and Princess Margaret Hospitals, University of Toronto, Toronto, Ontario