1. Public Health College, Harbin Medical University, Harbin, People's Republic of China.
2. Institute of Health Quarantine, Heilongjiang Entry-Exit Inspection and Quarantine Bureau, Harbin, People's Republic of China.
3. Public Health College, Jinzhou Medical University, Jinzhou, People's Republic of China.
4. Institute of Health Quarantine, Chinese Academy of Inspection and Quarantine, Beijing, People's Republic of China.