1. National Institute of Allergy and Infectious Diseases (NIAID), Bethesda, MD 20892, USA
2. College of Veterinary Medicine, Jilin University, Changchun 130062, China
3. Centre for Infectious Animal Diseases, Faculty of Tropical AgriSciences, Czech University of Life Sciences Prague, 165 00 Prague, Czech Republic
4. Section of Infectious Diseases, Yale School of Medicine, Yale University, New Haven, CT 06519, USA