Funding for this research was provided by:
National Natural Science Foundation of China (71573275 and 71974199)
Science Foundation of Liaoning Provincial Department of Education (LFWK201719)
Article History
Received: 22 July 2019
Accepted: 22 December 2019
First Online: 2 January 2020
Ethics approval and consent to participate
: The study protocol was approved by the Research Institutional Review Board of China Medical University, and it was exempt from institutional review board assessment due to the fact that it was conducted on the basis of the nationwide surveillance of infectious diseases in China and all the data were publicly open, supplied, and analyzed in an anonymous format, and without any access to the personal identifying information.
: Not applicable.
: The authors declare that they have no competing interests.