Funding for this research was provided by:
National Natural Science Foundation of China (91846303, 81390540, 81390544, 81390541)
Ministry of Science and Technology of the People's Republic of China (2011BAI09B01)
National Key R&D Program of China (2016YFC0900500, 2016YFC0900501, 2016YFC0900504, 2016YFC1303904)
UK Wellcome Trust (202922/Z/16/Z, 088158/Z/09/Z, 104085/Z/14/Z)
Kadoorie Charitable Foundation (None)
Text and Data Mining valid from 2019-11-04
Received: 5 May 2019
Accepted: 14 October 2019
First Online: 4 November 2019
Ethics approval and consent to participate
: The study protocol was approved by the Ethics Review Committee of the Chinese Centre for Disease Control and Prevention (Beijing, China: 005/2004) and the Oxford Tropical Research Ethics Committee, University of Oxford (UK: 025–04). All participants provided written informed consent before taking part in the study.
: Not applicable.
: The authors declare that they have no competing interests.