1. Institute of Microbiology and Epidemiology, Beijing, ChinaJunhui Zhai and Thomas Briese contributed equally to the manuscript.
2. Mailman School of Public Health of Columbia University, New York, New York, USAJunhui Zhai and Thomas Briese contributed equally to the manuscript.
3. Institute of Microbiology and Epidemiology, Beijing, China
4. Mailman School of Public Health of Columbia University, New York, New York, USA