Funding for this research was provided by:
Nanjing Municipal Science and Technique Foundation (ZDX12019)
Text and Data Mining valid from 2018-10-29
Accepted: 21 October 2018
First Online: 29 October 2018
Compliance with Ethical Standards
: KS is the developer of the CHU9D and took a small royalty in 2016 for a commercial licence. All other authors declare that they have no conflict of interest.
: The study protocol was reviewed and approved by the academic and ethical committee of Nanjing Municipal Center for Disease Control and Prevention. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
: All participants to both surveys provided written consent prior to participation.