1. Center for Endemic Disease Control, Chinese Center for Disease Control and Prevention, Harbin Medical University, Harbin 150081, China
2. Key Lab of Etiology and Epidemiology, Education Bureau of Heilongjiang Province & Ministry of Health (23618504), Harbin Medical University, Harbin 150081, China
3. Heilongjiang Provincial Key Laboratory of Trace Elements and Human Health, Harbin Medical University, Harbin 150081, China
4. Institution of Environmentally Related Diseases, Harbin Medical University, Harbin 150081, China