Funding for this research was provided by:
China National Key Research and Development Project (2018YFC1315300)
Received: 8 December 2019
Accepted: 14 May 2020
First Online: 3 July 2020
Ethics approval and consent to participate
: As all data was summarized from the China CDRS; the consent to publication is not applicable. The ethics committee at the Chinese Center for Disease Control and Prevention approved the study.
: No individual data is presented, and consent to publication is therefore not applicable.
: ADL is a Board Member for this Journal. Other authors have declared that they have no competing interests.