1. College of Medicine and Public Health, Ubon Ratchathani University, Warinchamrap, Ubon Ratchathani 34190, Thailand
2. Faculty of Medicine, Chiang Mai University, Muang, Chiang Mai 50200, Thailand
3. Pathology, Microbiology and Immunology, University of California, Davis, CA 95616, USA
4. Bung Borapet Research and Training Center, Mahidol University Nakhonsawan Campus, Nakhonsawan 60000, Thailand