1. CSIRO Materials Science and Engineering, Parkville, 343 Royal Parade, Parkville, Victoria, 3052, Australia
2. University of Wollongong, New South Wales, 2522, Australia
3. WHO Collaborating Center for Reference and Research on Influenza, National Institute of Infectious Diseases, Toyama 1-23-1 Shinjuku-ku, Tokyo 162-8640, Japan
4. National Institute for Animal Health, Tsukuba City, Ibaraki, Japan