1. Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
2. Department of Animal Health, Ministry of Agriculture and Rural Development of Vietnam, Hanoi, Vietnam
3. National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
4. Office of the U.S. Centers for Disease Control and Prevention in Vietnam, Hanoi, Vietnam