1. Stanley Ho Centre for Emerging Infectious Diseases, The Chinese University of Hong Kong, Hong Kong, China
2. S.H. Ho Research Centre for Infectious Diseases, The Chinese University of Hong Kong, Hong Kong, China
3. The JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China
4. Special Preventive Programme, Centre for Health Protection, Department of Health, Hong Kong Special Administrative Region Government, Hong Kong, China
5. Department of Medicine, Queen Elizabeth Hospital, Hong Kong, China
6. Department of Medicine and Geriatrics, Princess Margaret Hospital, Hong Kong, China