1. School of Public Health; Shandong University; Jinan Shandong China
2. Shandong Center for Disease Control and Prevention; Jinan Shandong China
3. Schools of Medicine; Fudan University; Shanghai China
4. Wuhan University School of Health Sciences; Wuhan Hubei China
5. Departments of Pathology and Microbiology and Immunology; University of Texas Medical Branch; Galveston TX USA