Funding for this research was provided by:
National Basic Research Program of China (973 Program) (2018YFA0606200)
Guangzhou Science and Technology Project (201704020194)
Natural Science Foundation of Guangdong, China (2019A1515011880)
Received: 7 July 2020
Accepted: 8 September 2020
First Online: 15 September 2020
Ethics approval and consent to participate
: The study was approved by the Ethics Committee of Guangdong Provincial Center for Disease Control and Prevention (2019025).
: Not applicable.
: The authors declare no conflict of interest.