Department of Epidemiology, Biostatistics and Occupational Health (Marasinghe), McGill University, Montréal, Que.; Departments of Microbiology, Immunology and Infectious Diseases (Cheaveau, Pillai), Medicine (Meatherall, Vaughan, Pillai), Pediatrics (Kuhn), Community Health Sciences (Zimmer, Pillai) and Pathology and Laboratory Medicine (Pillai), University of Calgary, Calgary, Alta.