1. Division of Infectious Diseases, State Key Laboratory of Biotherapy and Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, PR China
2. Capital Institute of Pediatrics, Beijing 100020, PR China
3. School of Life Science, Fudan University, Shanghai 200438, PR China
4. West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, Sichuan 610041, PR China