1. Department of Environmental Science, Policy and Management, University of California Berkeley, 137 Mulford Hall, Berkeley, California 94720-3114
2. Departments of Microbiology and Molecular Genetics and Medicine, University of California Irvine, 3012 Hewitt Hall, Irvine, California 92697
3. Division of Vector-Borne Infectious Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado 80522
4. Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado 80523