1. Department of Epidemiology and Biostatistics, The University of Georgia, Athens, Georgia, USA
2. Department of Mathematics and Computer Science, Western Carolina University, Cullowhee, North Carolina, USA
3. Colorado Department of Public Health and Environment, Denver, Colorado, USA
4. Department of Epidemiology and Biostatistics and Health Informatics Institute and Center for the Ecology of Infectious Diseases, The University of Georgia, Athens, Georgia, USA