Authors’ contributions
Xiaqing Zhang designed and conceptualized this study, and drafted the manuscript. Yao Wang and Wei Qin participated in the data collection and analysis. Yong Lyu and Wei Qin critically reviewed and supervised the development of the paper. Chengyang Hu, Pengpeng Xu, Liguo Ma, Lei Liu, Jie Sun, Yang Liu, Hui Yang, Fan Pan, Jieying Hu, Chengsong Cao, Kai Cheng, and Dawei Gao participated in the case investigation and the quality control of the epidemiological survey reports of all subjects. All the authors reviewed and edited the final manuscript.