Funding for this research was provided by:
National Special Science and Technology Project for Major Infectious Diseases of China (2018ZX10101002–002)
Received: 14 July 2020
Accepted: 22 September 2020
First Online: 1 October 2020
Ethics approval and consent to participate
: This article was based on analysis of routine surveillance data from NIPD, China CDC. The project leaders and staff led the review, analysis and interpretation of the data. No personal information was disclosed.
: Written informed consent for publication was obtained from all participants.
: Xiao-Nong is an Editor-in-Chief of the journal <i>Infectious Diseases of Poverty</i>. He was not involved in the peer-review or handling of the manuscript. The authors have no other competing interests to disclose.