1. Center for the Management, Utilization and Protection of Water Resources, Tennessee Technological University, Cookeville, Tennessee
2. Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
3. Instituto de Investigaciones Biomédicas, Universidad Autónoma de México, Mexico City, D.F., Mexico
4. Department of Medicine-Division of Infectious Diseases, Dalhousie University, Halifax, Nova Scotia, Canada