1. Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305, United States
2. Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30329, United States
3. Department of Civil Engineering, McGill University, 817 Rue Sherbrooke Ouest, Montreal, QB H3A 0C3, Canada
4. Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30329, United States