Text and Data Mining valid from 2019-11-29
Received: 13 September 2019
Accepted: 25 November 2019
First Online: 29 November 2019
Ethics approval and consent to participate
: This study was conducted according to the guidelines laid down in the Declaration of Helsinki and all procedures involving research study participants were approved by the Institutional Review Boards at Oxford University and the China National Center for Disease Control. Written informed consent was obtained from all participants.
: Not applicable.
: The authors declare that they have no competing interests.