1. Influenza Research Institute, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA
2. Department of Pathology, National Institute of Infectious Diseases, Tokyo, Japan
3. UW Health Clinical Laboratories, University of Wisconsin Hospital and Clinics, Madison, Wisconsin, USA
4. Department of Pathology and Laboratory Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA
5. Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan