Text and Data Mining valid from 2020-04-08
Received: 25 October 2019
Accepted: 28 March 2020
First Online: 8 April 2020
Ethics approval and consent to participate
: All studies had institutional ethical review approvals and obtained written informed consent from all participants.
: Not applicable.
: The findings and conclusions presented in this manuscript are those of the authors and do not necessarily reflect the official position of the US Centers for Disease Control and Prevention. The authors declare that they have no competing interests.