Acknowledgement
We thank Matt Moore (US CDC Hanoi) and Rogier van Doorn (Oxford University Clinical Research Unit, Vietnam) for scientific review. We recognized timely reagents supporting at beginning outbreak from WHO Collaborating Center for Reference and Research on Tropical and Emerging Infectious Diseases, Institute of Tropical Medicine, Nagasaki University, Japan.
We gratefully acknowledge the contribution of health workers at Center for Diseases Control and Prevention of cities and provinces in northern Vietnam. We also thank health care practitioners of the clinics and hospitals in Vietnam who supported the study.