1 Department of Toxicology, Henan Center for Disease Control and Prevention, Zhengzhou 450016, Henan Province, China.
2 Department of Epidemiology, School of Public Health, Zhengzhou University, Zhengzhou 450001, Henan Province, China.
3 Department of Infectious Diseases, the Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, Henan Province, China. Electronic address: huifen.feng@163.com.