1. Central Region Laboratory, Center for Research and Diagnostics, Centers for Disease Control, Taichung City 40855, Taiwan
2. Institute of Medicine, Chung Shan Medical University, Taichung City 40201, Taiwan
3. National Institute of Infectious Diseases, Tokyo, Japan
4. University of Malaya, 50603 Kuala Lumpur, Malaysia
5. Division of Enteric Infections, National Institute of Hygiene and Epidemiology, Vietnam