About the Authors
Virology and Immunology, Southwest Foundation for Biomedical Research, San Antonio, Texas, United States of America
School of Geography and Development, University of Arizona, Tucson, Arizona, United States of America
The authors have declared that no competing interests exist.
Conceived and designed the experiments: JC RR-H. Performed the experiments: JC HEB. Analyzed the data: JC HEB. Wrote the paper: JC HEB RR-H.