Funding for this research was provided by:
China Mega-Projects for Infectious Disease (2018ZX10711001, 2017ZX10104001 and 2018ZX10713-002)
the China 13th Five-Year National Science and Technology Major Project and the key R & D Program of Hunan Province (2018ZX10713002 and 2017SK2101)
Text and Data Mining valid from 2019-07-01
Received: 15 March 2019
Accepted: 14 May 2019
First Online: 1 July 2019
Ethics approval and consent to participate
: All aspects of the study were performed in accordance with national ethics regulations and approved by the Institutional Review Boards of the National Institute for Viral Disease Control and Prevention, Center for Disease Control and Prevention of China.
: Not applicable.
: All the authors approved the final manuscript and they have no competing interests to declare.
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