1. Department of Epidemiology, School of Public Health, Air Force Medical University, Xi’an, China
2. Ministry of Education Key Lab of Hazard Assessment and Control in Special Operational Environment, Xi’an, China
3. Centre for Disease Prevention and Control in Northern Theater Command, Shenyang, China
4. Lintong Rehabilitation and Convalescent Centre, Xi’an, China
5. Department of Epidemiology, School of Public Health, Gansu University of Chinese Medicine, Lanzhou, China