1. Tianjin Centers for Disease Control and Prevention, Tianjin, China.
2. School of Nursing, University of Pennsylvania, Philadelphia.
3. National Centre for AIDS/STD Control and Prevention, Chinese Centre for Disease Control and Prevention, Beijing, China.
4. Tianjin Dark Blue Working Group, Tianjin, China.
5. Tianjin Hongqiao District Center for Disease Control and Prevention, Tianjin, China.