Wing Wai Yew1, Denise P Chan1, Kwok Chiu Chang2, Ying Zhang3. 1. Stanley Ho Centre for Emerging Infectious Diseases, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China. 2. Tuberculosis and Chest Service, Centre for Health Protection, Department of Health, Hong Kong, China. 3. Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.