Funding for this research was provided by:
Beijing Science and Technology Planning Project (Z201100005420010)
National Key R&D Program of China (2019YFB2102103)
National Natural Science Foundation of China (92046010, 82161148011)
Received: 26 January 2021
Accepted: 14 April 2021
First Online: 7 May 2021
: Ethical approval and informed consent requirements were waived by the Institutional Review Board and Human Research Ethics Committee of the Beijing Center for Disease Prevention and Control (Beijing CDC) because this study was considered a continuation of the public health investigation associated with an emerging infectious disease.
: Not applicable.
: The authors declare that they have no competing interests.