Funding for this research was provided by:
Beijing Science and Technology Planning Project (Z201100005420010)
Received: 22 April 2020
Accepted: 14 July 2020
First Online: 20 July 2020
Ethics approval and consent to participate
: Data collection and analysis were determined by the National Health Commission of the People’s Republic of China to be part of the continual public health investigation of an emerging outbreak and thus the informed consent and ethics approval was waived by institutional review board and human research ethics committee of Beijing Center for Disease Prevention and Control.
: Not applicable.
: The authors declare no competing interests.