1. Center for Endemic Disease Control, Chinese Center for Disease Control and Prevention, Harbin Medical University, Key Lab of Etiology and Epidemiology, Education Bureau of Heilongjiang Province & National Health and Family Planning Commission (23618504), Harbin, China
2. Department of Science and Education, Bayan Nur Hospital, Bayan Nur, China
3. Department of Public Health, Dalian Health Development Center, Dalian, China